Post #602: Radical change in CDC guidance, and implications for your behavior.

Source: COMMENTARY: COVID-19 transmission messages should hinge on science. March 16, 2020, Lisa Brosseau, ScD, author, on line at the University of Minnesota Center for Infectious Disease Research and Policy.

In the illustration above, Person A has COVID-19 but doesn’t know it.  He’s talking loudly and at close range to person B, who soon will have COVID-19.  Person C is standing to the side, wondering why none of them are wearing masks.  Presumably, this snapshot was taken in an android nudist colony.

In all seriousness, go read that article if you want to know what’s probably going on with the continued spread of COVID-19.

Continue reading Post #602: Radical change in CDC guidance, and implications for your behavior.

Post #601: If you don’t want to spend a month slowly suffocating to death …

Note to regular readers:  This is a compendium of everything I think I know about the current pandemic.  Some material repeats prior posts.  I am hoping to get wider distribution of this once it is finished.  But I have been told that this is a hard post to read.  All I can say is, read it anyway.

By Christopher Hogan, Ph.D.

If you don’t want to spend a month slowly suffocating to death, the CDC has a tip for you:  Wear a mask.  Wear one any time you’re around people other than your immediate family.  That won’t guarantee that you’ll avoid dying from COVID-19 (SARS-CoV-2), but it will improve your odds.  And it will improve everyone else’s odds as well.

Sure, you need to keep doing everything else that the Centers for Disease Control (CDC) has recommended.  Wash your hands and maintain your distance.  Wash your hands and avoid touching your face.  Disinfect commonly-touched surfaces in your home.  And then wash your hands again.  But now, in addition, wear a mask whenever you are around people other than your immediate family.

As I write this, it looks like we’re about a week away from inevitable mass deaths in New York City.  That’s going to happen when they run out of ventilators and they start just letting people die.  Not because they want to, but because there will be no other option.

We don’t know, yet, whether other parts of the country will end up in that position or not.  Including the Washington DC area.  We’ve taken the gamble that “social distancing” will break the back of this pandemic.  But in fact, nobody knows whether our “soft” approach to social distancing will slow the spread  enough.

In effect, we are in the middle of a vast experiment.  Performed ad-hoc, one city or state at a time.  And we’re the guinea pigs.

Or maybe sheep would be a better analogy.  Because, by and large, We the People have been sitting around, hoping that our various government leaders will solve this problem for us.  And we are now finding out that, outside of the US Army Corps of Engineers, not only is the Federal government not helping, it has actively been getting in the way.

In two critical ways, business-as-usual mistakes by two Federal agencies have made things vastly worse.  And those two key mistakes dovetail in such a way as to increase your risk of death materially.

But before I get into that, let me remind you of what, exactly, we’re talking about.  In so far as a person can know, absent first-hand experience.


What will it be like to die from COVID-19?

The short answer is that it will take a while, you’ll be alone, and you’ll be on a ventilator as you slowly suffocate to death.  That means that you will be confused, unable to move and likely delirious when you are conscious.

And that’s the best-case scenario.  That assumes you get into a hospital, a ventilator is available, and the drug stocks hold out.

First, it will take a while.  World Health Organization analysis of the Chinese experience suggests that, among decedents, it typically takes two to eight weeks from diagnosis to death.  Given that this type of data typically has a “long right tail”, a good guess for the median would be about three-and-a-half weeks.  But that’s awkward to say, so let me just say “about a month”.

Second, you’ll be alone:  You’ll never see your family again.  Hospitals are no longer allowing visitors, almost without exception.  Looking at Inova as an example, they say they make an exception for (e.g.) some end-of-life situations.  But not in the case of COVID-19.

"Visitation will not be allowed for suspected or confirmed patients with COVID-19."

The upshot of that is that if you die in the hospital, from the time of admission to the time of death, you (or your loved one) will never see family or friends again.  You won’t have any way to know that, ahead of time, because you don’t enter the hospital expecting to die.  But that will be the outcome, after the fact.

Third, you’ll be on a ventilator for some time, with all that entails.  In most if not all cases, they have to dope you up, eventually, so you don’t “fight the ventilator”.  So, you’ll be not-quite-unconscious, and not-quite totally unable to move.  And being in that ICU environment for any length of time makes many people literally go crazy, as in, experience delirium (as in ICU psychosis).


Two big mistakes.

OK, with that firmly in mind, let’s move on to the two big mistakes our Federal government has made.  So far.  And a third big mistake that we need to prevent. And then, finally, what we can do, for ourselves, as a sort of mid-course correction.


Mistake 1:  The N95 mask shortage and the Food and Drug Administration rules

I used to be self-employed as a health economist.  And  I still get a lot of business-to-business emails.  One of those landed in my in-box yesterday.  It was a legitimate offer to sell me up to 5 million N95 and KN95 masks per month.  If I only need a few — 100,000, say — they could get them to me in three to five days.  Larger orders would take a bit. The masks cost about $3 each.  Free shipping.

My first thought was, what alternative universe did that come from?  All I read is that we have a huge shortage of those N95 masks.  So much so that it is our patriotic and ethical duty to leave those for the health care workers.  You, as a good citizen, need to accept a small additional risk of death, so that front-line health care workers and first responders don’t have to take a much larger risk.  Just look on Amazon, and you’ll see those clearly marked “Hands Off” for the general public.

If they’re in such short supply, how can this joker offer me 100,000 masks by next Wednesday?  (Not me personally, of course, he mistook my business as one that actually provides health care.)  And what the heck is a KN95, anyway?  I thought they were called N95.

Well, as it now turns out, it looks like that shortage was, in some large part, the result of our shooting ourselves in the foot.  And now, months into the US portion of the pandemic, the Food and Drug Administration has graciously, if ever-so-slowly and ever-so-grudgingly, decided to stop doing that.

The FDA would not allow Chinese-made N95-equivalent masks (“KN95”) to be used in US hospitals.  If you look at the full specs for N95 and KN95 (here, from 3M, in a .pdf), they are virtually identical.  I believe the FDA’s concern was not about the performance of the masks, but instead about the potentially insecure supply chain (i.e., you might get sold knock-offs).

But as of two days ago, the FDA changed its mind.  Apparently after numerous people yelled at them for the stupidity of their actions, including a petition that collected thousands of signatures of front-line health care personnel. Just read it on Buzzfeed.

And as a result, yesterday I got that email.  It was from a well-established firm whose main line of business is helping other companies sell to the Federal government.  They’re deal-makers, for want of a better term.  And right now, they’re in the business of arranging import of KN95 masks from China.  They were ready to go the day the FDA dropped the ban.  And I doubt that they were the only ones in that position.

So I expect our mask shortage to begin easing soon.  Through the simple expedient of buying them.  And it only took us a few months to think of doing that.  Better late than never, I guess.

For the time being, consumers should still refrain from buying them.  Leave what we have for health care workers and first responders.  For now.

And, as far as I can tell, anything you want to know about masks, that is known, you can find on the Smart Air website.  If you have a question, look there first.  I have no idea who those folks are, but I am glad they are sharing their knowledge.


Mistake 2: CDC guidance and its misunderstanding of how COVID-19 spreads.

Let’s briefly review what has changed, now that the CDC has quietly added “wear a cloth mask” to its guidance to the public on dealing with COVID-19.

A week ago, CDC was saying that COVID-19 was primarily spread by droplet transmission from symptomatic individuals.  And so, in effect, stay out of range of droplets when an obviously sick person coughs or sneezes, and hey, you’ll be OK.  Keep your distance and wash your hands.  Social distancing will keep you safe, so there’s no need to wear a mask.

Anyone who was paying attention realized that couldn’t possibly be right.  You really couldn’t explain the spread of disease that way.  I mean, do you really think they let somebody who was coughing and hacking anywhere near the Prime Minister of Great Britain in the past few weeks?

Even for hoi polloi, that explanation wasn’t credible once social distancing was in place.  Based on the handful of shopping trips I have made in the past three weeks, nobody is stupid enough to be out in public with symptoms of COVID-19. The idea that this is mainly spread by people coughing and sneezing is just plain nuts.

Not-being-sick-in-public is now a rigidly-enforced social norm.  Last time I was in the Safeway, somebody, somewhere in the store, coughed.  And we shoppers reacted like a herd of startled deer.  Heads came up.  Eye contact was made.  Everybody made that little “wasn’t me” gesture.  These days, you’ll get some hard looks if you so much as clear your throat loudly in the grocery store.

Finally, just do the simple arithmetic.  COVID-19 has a median incubation period of 5 to 6 days, based on the Chinese experience.  In Fairfax County, my home, schools have been closed for more than three weeks now.  And yet, the count of cases continues to climb at an accelerating rate, with Fairfax expected to top 400 cases today.  Do the math.  We’re now seeing our third or fourth generation of new infections since the start of serious social distancing.  If “stay out of range when sick people cough” was all it takes, we wouldn’t be seeing this.

Today?  Now CDC says, well, maybe this is being routinely spread by asymptomatic individuals.  People who don’t look sick, feel sick, or sound sick.  Maybe you don’t have to cough or sneeze, because most people spew tiny droplets simply by talking.   And — not clear if they are saying it or not, but true nevertheless  — clearly some of this is aerosol spread, for which, indoors, there is no “out-of-range”.

And so, as their understanding of the facts has changed, the CDC has changed its mind.  Everybody needs to mask up in public.  Social distancing is not enough.  Particularly not when the head of the Chinese CDC called failing to require masks in public “the big mistake” that the US and Europe were making. Presumably, he would know.

So the CDC is finally getting it.  This disease is a lot easier to spread than they thought.  And it’s not being spread by obviously sick people.  So everybody needs to wear a mask, all the time, when you are in public around others.

In addition to droplet transmission, we need to start having public discussion of the potential for aerosol (airborne) transmission (particularly close-range aerosol transmission) and superspreaders.   Because at this point, it’s clear that the CDC isn’t going to be doing that despite clear evidence that it has occurred.  And, so, without an explicit warning from the CDC, we risk that it will continue to occur.

(If you read nothing else, go read the University of Minnesota, Center for Infectious Disease Research and Policy piece that explains the importance of close-range aerosol transmission.  My takeaway from that is that, arguably, the stupidest thing we can be doing, right now, is to stand six feet apart and talk at each other, loudly, with no masks on.)

Everyone needs to read about the safely-conducted, properly-socially-distanced, hand-sanitized, no-hugs choir practice that resulted in 45 infections and two  deaths (so far), out of 60-member choir.  That’s aerosol spread.  There’s no way to be sure, but that’s plausibly due to a single infected individual who was a superemitter of aerosols.

And that’s the kind of event that may continue to happen if we don’t educate ourselves about it. (But in groups no larger than ten, these days, in Virginia).  Because at this point it’s clear that the CDC isn’t going to do that for us.  Possibly for fear of panicking the public.  Possibly because they believe their epidemiological evidence rules that out as a common transmission route outside of the hospital.  (But inside the hospital is a different story.  The threat of aerosol transmission is the main reason they need those N95 masks instead of common surgical masks, and why the US Army Corps of Engineers has worked up an expedient way to convert hotel rooms to negative-pressure rooms for housing the overflow of COVID-19 patients.)

But we also have to say what needs to be said:  So far, the CDC has been dead wrong about how this virus routinely spreads.  They kept telling the public that coughing and sneezing by clearly sick individuals was the problem.  And so, social distancing and hand washing was the answer.  You can’t really blame the CDC, because droplet transmission by symptomatic individuals is what the WHO analysis of China (cited above) said.  But it’s still wrong.  And you have to wonder why, up to now, they continued to ignore the potential for widespread transmission by asymptomatic individuals.  Maybe the thought that was just too scary for us to handle?

In any case, however they got there, they have now come to realize that a lot of the spread must be via asymptomatic individuals. As had anyone else who has been paying attention.  Because nobody with symptoms of anything is going out in public any more.

But they’re still focused on droplet transmission, and they aren’t going to mention aerosol transmission.  Maybe that’s because they have evidence that strongly supports that.  Maybe they won’t mention it because they don’t want a run on the N95 masks needed to filter out aerosol-sized (five micron or smaller) droplets.  Or maybe because they think that’s just too scary for us to handle.  However you slice it, after this first about-face on the typical transmission route, I’m not sure it means anything that the CDC isn’t talking about aerosol spread.

The CDC is mum on this topic despite that certain knowledge that many historical and current contagious diseases were characterized by aerosol transmission.  Those include both bacterial disease such as tuberculosis and viral diseases such as Ebola and some forms of influenza.

And in this case, there’s an old saw that clearly applies.  It ain’t what you don’t know that gets you into trouble.  It’s what you know for sure that just ain’t so.  Every thinking American took the CDC guidance as an indication of what they knew about how this disease spreads.  And, as it turns out, that just wasn’t so.

If aerosol spread is a probable route of transmission, we’re unknowingly making a major public health blunder by standing around talking loudly to each other.  Speech generate large volumes of aerosol-sized (5 micro or smaller) droplets.  Loud speech generates more.  And singing generates those droplets at roughly the same rate that coughing does.  Which is, in all likelihood, how almost that entire choir got infected from a single choir rehearsal.

No mask that you can ethically buy right now will stop all, or even most, of those tiny aerosol droplets.  Your only option, for benefit of us all, is to try not to generate them.

So shut up when you are in public.  That’s advice the CDC needs to offer us, but can’t.  Because, for whatever reason, they won’t engage in public discussion of the potential for aerosol transmission.  We need to do that for ourselves.  So far,  “superspreader” events like that choir rehearsal are almost unheard-of.  Let’s hope it stays that way.


The synergy of those two mistakes.

So now the CDC has added a wishy-washy bit of advice to their guidance to the public:  Wear a cloth face covering.  Wear a cloth mask, if you will.

Why cloth?  That pretty much means that every American has to make one, borrow one, or scrounge one up.  Is there something beneficial about cloth masks?  Do they perform well.

No.  The recommendation for cloth masks isn’t to protect you, the wearer, very much.  With luck, skill, and diligence, a face mask made out of cloth can be constructed so as to provide nearly as much protection to the wearer as a standard hospital surgical mask.  If you happen to make the right choice of fabric, you can filter out aerosol particles almost as well as a standard surgical mask.  But it’s a good bet that the typical cloth mask won’t come up to that standard.

Wearing a cloth masks probably does help protect others, in the event that you’re infected but don’t know it yet.  I keeps you from spreading disease by capturing or at least slowing the velocity of the droplets you emit.  So that’s a plus, and that’s the public health benefit.  But wearing a commercially-made mask would probably do a better job of that, too.

The guidance to use a cloth mask is there because the CDC is afraid of exacerbating the N95 mask shortage.  Commercially-produced masks are better (surgical mask), and sometimes vastly better (N95 respirator), than what the typical American is going to be able to whip up on the fly.  The guidance to wear a cloth mask is to keep the public from purchasing those “real” masks.

But no reputable seller has N95 masks for sale to the public.  Just look on Amazon.  See what Home Depot has done.  Any reputable entity that could channel a large number of such masks to the public has withdrawn those from the market.

And, see Mistake 1.  With the lifting of the ban on use of KN95 masks, and the realization that standard N95s and similar masks can be filter air effectively for vastly longer than a single use, with relatively little risk if appropriate protocols are adopted, it’s a fair bet that this N95 mask shortage is simply going to disappear as a factor in the future progress of this pandemic.

And yet, it’s the heart of current CDC guidance.  Will that change in the near future, if the mask shortage abates?  I guess we’ll see.

What has me truly irked, of course, is how the FDA exacerbation of the N95 mask shortage dovetails with the CDC decision not to recommend masks in public.  If you think about it, if these two agencies had done this differently, there’s some chance that we could have all been wearing KN95 masks whenever we were out in public.  Or, maybe, all the people in New York City could have been wearing KN95s whenever they were in public.  And maybe it’s not too late to make that happen.  Bet that would have altered the course of this some.

If the importation of large numbers of KN95 masks from China resolves the current N95 shortage, the next city to approach the situation that New York is in will have the opportunity to issue those effective, commercially-available masks to citizens and enforce wearing them in public places.  Before they run out of ventilators.

The whole point of an N95 mask (technically, respirator) is that, when properly worn, very little gets through it.  It’s effective at stopping even the most difficult-to-catch size of aerosol particle (0.3 microns).  Nothing is a perfect, but that’s (very nearly) as good as it gets.  (Unless you want to wear a half-face or full-face respirator.)  And that, and hand washing, and social distancing, would seem to up the odds of breaking the back of this pandemic.  If we can solve the current and apparently self-inflicted mask shortage, we need to start thinking of the strategic deployment of those masks to the citizenry, and enforcement of public mask use.


Will vaccine development be the next big Federal mistake?

Edit:  Upon re-reading this the next day, I think I overstated the case for skipping Phase I trials in this emergency, slightly, so let me clarify.  But I still conclude that it would be smarter to proceed directly to Phase II, in terms of total lives lost.  You will need to read the rest of this section, then come back and re-read this. 

What I forgot in the first draft of this is that vaccine trials have a unique feature:  You can use the Phase I trial to see whether or not vaccine recipients develop the appropriate antibodies.  That can prevent you from going on to Phase II, and needlessly exposing a cohort of individuals to coronavirus with a vaccine that has no chance of success.  Further, if you move directly to Phase II, and expose the patients to disease, that would confound your ability to determine whether or not patients developed antibodies from the vaccine alone.

That said, somebody needs to do the estimate of total lives lost under two scenarios:  Business-as-usual:  Take the N months required for Phase I, and ultimately distribution the vaccine X + N months down the road.  Emergency approach:  Skip Phase I, and distribute it a X months down the road. 

To some degree, that calculation depends on what you think the state of the world will be X months from now.  That is, how many people you think will die in the period from X to X + N.  If you are convinced that this will be under control, you might judge that fewer lives would be lost under business-as-usual.  If not, you’d judge that fewer lives would be lost with the emergency method.

Given that the total number of people in the vaccine trial will likely number in the hundreds, while the number of people at significant risk of dying from COVID-19 will likely still be in (at least) the tens of millions, I’m almost sure that under any plausible scenario, fewer lives would be lost under the emergency methods that skips Phase I. 

That’s all I’m trying to say.  The text of my original post follows.

So far, there’s scant information available to the public on what the Federal government is doing to produce a vaccine.  But I can tell you, from what I’ve read, and based on what we’ve seen from FDA and CDC so far, I’m not betting on seeing one any time soon.

What sets me off on this topic is the report that the Federal government was starting Phase I trials of a vaccine.  To which I said, why in the hell are they doing that?  Allow me to explain.

Drug development goes through three phases.  Phase I simply tests whether or not the drug will kill you.  Is it safe?  It doesn’t actually do anything to test whether or not it works.  (Edit:  See above.  You do test development of antibodies.)  Phase II is where you start to test whether the drug works or not, and typically tries a few different dosing regimens to see what works best.  Then Phase III re-tests whether it works, using the most promising dosing regimen.

There’s no barrier to skipping Phase I.  If the proposed vaccine kills people, you’ll find that out in Phase II.  (Edit:  And so, if the vaccine could have been discarded as ineffective in Phase I, you risk needlessly killing some of the treatment group by skipping that, but gain lives saved by delivering an effective vaccine sooner than you otherwise would.) And normally, under business-as-usual, sure, you wouldn’t want to take a risk of killing a large number of people.  So you do a small Phase I trial first.  Take a few months, go slow, don’t push it.  Just on the off-chance that what you’ve developed is particularly deadly.

But in this case, every day that we don’t have a vaccine is a day that more people die.  What are we up to now, about a thousand a day?  Is that going to double or triple when New York City hits the wall?  How long is that going to go on?

Skipping straight to Phase II risks killing a few more people than you might have otherwise.  On the other hand, how many additional deaths will result from each additional day of delay in creating this vaccine?  Has anyone even bothered to do the cost-benenfit analysis of Phase I in this case? 

Or, as I suspect, is this just another example of a Federal agency that can’t shake itself loose from its business-as-usual attitude?  On the one hand, they realize this is a national emergency. They press forward with all due haste.  But on the other hand, it never even occurs to them to skip Phase I.  Or, if it does, the people making their decisions, within their own silos, are not being forced to see the big picture.

The question of how many deaths for each day of delay is not an idle one.  That will will depend on the state of the pandemic at the point when the vaccine is ready for distribution.  Maybe our current state and local experiments in social distancing will pay off, and nobody will be dying from this 12 to 18 months from now.  In that case, sure, take your time.  On the other hand, maybe we’ll never get this fully under control, and we’ll still be looking at 1000 deaths a day, 12 months from now.  In which case, in hindsight, this will be yet a third example of business-as-usual by a Federal agency being exactly the wrong choice.

So it’s a gamble, and I’m not sure our Federal government realizes it.  Phase I makes perfect sense — if you think all the dying will be over before the vaccine is ready.  Phase I is lunacy if you don’t.  If it were up to me, I’d hedge my bets in favor of developing this as rapidly as possible, just in case we’re still dying from this, in large numbers, a year from now.


But back in the real world, citizens are not taking this seriously enough.

Based on my last trip to the grocery store, it’s clear that many people and some major corporations still haven’t gotten the message.  Yesterday, at my local Safeway, maybe a third of the employees were wearing masks.  And at least some employees were not maintaining social distance. I expected to see that sort of thing among the shoppers, and did.  Some people are hopelessly stupid and there’s not much you can do about it.  But I did not expect that from a major US corporation with a huge number of public-facing employees.

Just do the math:  My home, Fairfax County, has 400 known cases of coronavirus and about 800,000 adults.  Based on the recent daily growth, it’s fair to say we likely have at least one case of undetected coronavirus per 500 adults, right now.  That Safeway is the largest one on the East Coast, so I’m guessing they have 2000 people a day walk through there, even with this pandemic.  With those numbers, the odds are overwhelming that those Safeway employees are being exposed to coronavirus, right now, every day. 

And what do I see?  No masks, no sneeze guards at the registers, no enforcement of social distancing.  No nothing.  For the single largest grocery store in the area.

My wife called the manager to complain, and got a classic corporate non-response.  Safeway says its up to each individual employee to wear a mask or not.  A corporation with a huge public-facing staff, and their policy is, every man for himself.

I’m still trying to figure out whether they are unaware of the almost-certain daily exposure of their staff, or they just don’t care.  The only thing I know for sure is that I’m not going back there until this pandemic is over.  Maybe never.  And that’s from a loyal life-long Safeway shopper.

Doesn’t anybody get this?  We haven’t fixed it.  We hope we’ve fixed it, sure.  But there’s no guarantee that our various half-hearted attempts at social distancing will, in fact, work.  Look at what China imposed in Wuhan, then go to your local grocery store and see what’s going on.  The game isn’t over yet.  The fat lady has not yet sung.  I don’t think we’ve reached an inflection point (where the daily increase in cases begins to decline) in any US state yet.  For sure, we haven’t reached that in the Commonwealth of Virginia.

And the clerks at Safeway aren’t wearing masks.  Official corporate policy at the largest grocery store in the County is, eh, wear ’em if you want to.  This is so wrong.  We need to start thinking of getting ahead of the curve, not acting like a bunch of sheep.

So, for damned sure, I’m not going to spend another penny on a vendor who is too lazy, or too foolish, to require all public-facing personnel to mask up.  Not if I have any alternative.   I suggest that all of you do the same, and maybe that will speed them along toward eventually figuring this out.

We, as a country, are in the process of running out of hospital beds, masks, respirators, and staff.  As we scramble to build temporary hospital space, now more than ever, public health officials need to keep in mind the reverse of Roemer’s Law:  A bed not filled is a bed not built. 

We as citizens, have an obligation to ourselves not to be the moron who fills the next bed.  Morally, I’m a Darwin Awards fan.  I really have little objection to stupid people getting themselves killed for their stupidity.  But in this case, with beds and ventilators in scant supply, stupidity is going to kill a lot of innocent bystanders.  If our current lackadaisical attitude results in filling all the beds by the time I catch this disease, then I’m going to be the one left to suffocate slowly at home.

Unsurprisingly, I object to that.


Summary:  What can you do?

Rule 1:  Don’t be the dumbass who fills the next available hospital bed.

The big change this week is that the CDC has finally figured out that this is being spread by people who are infected, but don’t have symptoms.  You need to act as if you are one of those people.  And you need to act as if everyone you meet outside of your immediate family is one of those people.

Outside of your home, treat yourself and everyone else as potential carriers of coronavirus.  Not because you’re paranoid.  But because its true.

First, minimize trips to public places.  Given the shortage of delivery slots for groceries, I’ve decided to continue grocery shopping in person.  And, while I’m there, I pick up a few things for relatives and neighbors.  There’s no sense having three people in the grocery store when it only takes one.

Two, do what the CDC tells you to do.  Wash your hands.  Maintain a 6′ distance.  Wash your hands.  Don’t touch your face. Wash your hands.  And if you even think you might be sick, stay home.

Three, wear a mask when you are in public around other people.  In particular, wear a mask whenever you find yourself talking to someone, in person, outside of your immediate family.

Fourth, unless and until the CDC can firmly rule out aerosol transmission of this disease, keep your voice down when in public.  Ideally, just keep your mouth shut, because talking releases large numbers of aerosol particles.

Fifth, wear the best mask that you own, right now.  If you don’t own one, ask around.  If you have to make one, there are plenty of plans available.  And I’ll give you my tip:  The smart people have figured out that the best possible material for use in an expedient (home-made) mask is the inside of a high-end furnace filter.  I’ve heard Filtrete 1900 or better.  I’d accept MERV-13 or better.  See Post #593 for details.  If you have access to materials like that, incorporate them into your home-made mask.

Sixth, if the importation of KN95 masks solves the mask shortage, the Federal government needs to step up and target any excess to hard-hit cities and towns.  And those cities and towns need to distribute those, and enforce public mask use by ordinance.

Seventh, urge your city or town to enforce public mask use by ordinance.

Eighth, boycott any business that does not require all public-facing employees to use masks, or a least puts them behind a sneeze guard or some other effective barrier.  In my area, it’s a sure bet that employees in the largest retail establishments are now being exposed to coronavirus on a daily basis.  Corporation who can’t figure that out don’t deserve your money.

Ninth, write your Congressman and urge all possible haste on vaccine development.  We really have no clue what things are going to look like a year from now.  Bureaucracies stick to business-as-usual unless and until somebody screams at them loudly enough.  Maybe we all need to start screaming.

Finally, consider establishing a mask-distribution program in your immediate area.  Mail-a-Mask, or some such.  People who have them, or have the skills to make them, offering them to their neighbors.

Post #600: Farmers’ market followup

This is a followup to Post #583.

I emailed the people who run the Central Markets farmers’ market, and they will continue to hold their farmers’ market at the Holy Comforter church on Sundays.  The next date is now explicitly shown on their website.

If aerosol transmission of this disease actually does occur frequently, and vendors won’t wear masks, then an open-air market on a windy day is probably your safest bet for shopping, and long as the density of individuals is kept low.

If you go, you should wear a mask of some sort.  Get ahead of the curve.

Post #599: Safeway, are you crazy? Or just stupid? CORRECTED

On the plus side, the Safeway was nearly fully stocked.  Yes, they have bananas.  Produce was fully stocked.  Butter and eggs were there, but skimpy.  Milk was little moth-eaten, but anything you’d want, they had some.  Still light on cooking oil.  Rice was fine.  Poultry was still a little scanty (but they had chicken wings at $0.99/lb).

All in all, they are to be commended on getting on with their business.  Except for TP, the place looked more-or-less normal.

On the minus side, many employees were not wearing masks.  Many employees were not maintaining “social distance” from each other.

I mean, sure, I expected some of the customers to ignore the current CDC guidance.  And, in the past, because CDC said we didn’t need to wear masks in public, I could forgive stores that didn’t impose that on employees.  No matter how foolish I thought that was.

But now?  Grocery store clerks, including at checkouts, not wearing even a rudimentary mask? Other stores are at least putting up plastic guards between customer and checkout clerk?  Not here.

I am a loyal, lifelong Safeway customer.  When they shut their Vienna store, I dutifully began shopping at Pan Am.  And I’m not going back there until the epidemic is over.  Maybe not even then.  Not if I can find a store that will follow anticipate current CDC guidance.

Let’s briefly review what has changed.

A week ago, CDC was saying that COVID-19 was primarily spread by droplet transmission from symptomatic individuals.  So, stay out of range of droplets when an obviously sick person coughs or sneezes, and hey, you’ll be OK.  No need to wear a mask.

That obviously wasn’t right.   You really couldn’t explain the spread of disease that way.  I mean, do you really think they let somebody who was coughing and hacking near Boris Johnson?  I don’t.

Today?  Now CDC says, well, maybe this is being spread by asymptomatic individuals.  Don’t look sick, don’t feel sick, don’t sound sick.  Maybe you spew droplets just by talking.  No sneezing or coughing needed.  And — not clear if they are saying it or not, but true nevertheless  — clearly some of this is aerosol spread, for which, indoors, there is no “out-of-range”.

(If you don’t understand droplet versus aerosol, look them up in my prior posts.)

And so, the facts have changed, and the CDC has changed will soon change its mind.  Everybody needs to mask up in public.  Social distancing is not enough.  Particularly not when the head of the Chinese CDC called failing to require masks in public “The big mistake” that the US and Europe were making.

This disease has a median 5 to 6 day incubation period.  That’s the time lag between when you are infected, and when you feel ill.  Fairfax County Schools have been closed for 21 days now.  I assume we’ve all been doing our social distancing during that time period.  And today, Fairfax is set to record its 400th case.

Surely we can all do math here, right?  We are seeing new cases that had to have been infected way, way after the start of social distancing.  COVID-19 is still spreading, for now, despite social distancing. 

Doesn’t anybody get this?  We haven’t fixed it.  We hope we’ve fixed it, sure.  But there’s no guarantee that our various half-hearted attempts at social distancing will, in fact, work.  Look at what China imposed in Wuhan, then go to your local grocery store and see what’s going on.  The game isn’t over yet.  The fat lady has not yet sung.  I don’t think we’ve reached an inflection point anywhere in any US state yet (but I have not checked that). 

And the clerks at Safeway aren’t wearing masks.  So we are living by Rule #6:  Yes, the really can be that stupid.  Not the clerks.  I mean the people who run Safeway.

The CDC finally wised up.  We all need to follow the CDC advice.  The new advice, that reflects their current understanding of the facts.

Edit:  Well, I was not right.  I guess I read a description of what their advice might be.  But right now, the CDC is still kind-of, sort-of, maybe talking about someday asking (but not requiring) Americans to wear a mask in public.  I can’t even imagine what they are dithering about. But the bottom line is that they still have not modified their official guidance regarding use of masks in public places.

And here’s why they need to get on the stick.  My wife called the Safeway and talked to the manager, and he said that nobody had called for public mask use, so it’s up to each employee to do what they want with regard to mask or not.  That said, I’m sticking by my original conclusion.  We need to start thinking of getting ahead of the curve, not acting like a bunch of sheep.

 Again, do the simple arithmetic.  Fairfax has about 800,000 adults.  And as of today we’re likely to reach our 400th known can of COVID-19.  One in 2000 adults is known to have been infected.  Do you think 2000 adults shop at the Pan Am Safeway on a given day?  I’d bet so.  So, I’d say the odds are pretty good that the clerks in that store are getting exposed on a regular basis.  Day in and day out.  It’s really stupid not to provide them with some protection.  And it’s really stupid of me to shop at a store that does not provide and require at least some minimal protection for public-facing staff.

And, for damned sure, I’m not going to spend another penny on a vendor who is too lazy, or too foolish, to require all public-facing personnel to mask up.  Not if I have any alternative.   I suggest that all of you do the same, and maybe they’ll eventually figure it out.

Post #598: Mask shortage?

Following up on the last post, I used to be self-employed as a health economist.  And so I still get a lot of business-to-business emails, from folks who think that I was, in fact, a “real” business.

You know this N95 mask shortage that’s happening now?  Well, as it turns out, that might have been the result, at least in part, of our shooting ourselves in the foot.

The FDA would not allow Chinese-made N95-equivalent masks (“KN95”) to be used in US hospitals.  If you look at the specs for N95 and KN95, they are virtually identical.  I believe the FDA’s concern was insecure supply chain (i.e., you might get sold inferior knock-offs).

But as of late yesterday, they changed their minds.  Apparently after thousands of people yelled at them — including circulating a petition — for being stupid.

Read it on Buzzfeed.

So, luckily, they’ve now figured out that, eh, maybe that wasn’t so smart.  And they are allowing them to be used on a caveat emptor basis.  They are still not certified for use in US hospitals.  But if you want to use them, you can.

Today I got an email, from a well-known (i.e., not fly-by-night) company whose line of business is helping other companies sell to the Federal government.  They’re deal-makers, for want of a better term.  Among other things, they’re connected with an Ohio mask manufacturer.  But in the meantime, they’re in the business of arranging import of KN95 masks from China.

I’m just going to summarize their apparently legitimate offer.

Anything under 100,000 KN95s, they’ll charge you $3/mask, and get them to you in 3 to 5 days.  Same offer on N95s, they just cost twice as much.

Want a half-million KN95 masks?  Under $3 each, takes 5 to 10 days.  Half-million N95s?  Twice as much, 7 to 14 days.

If you want, say, 10 million or more, they’re slightly cheaper, but it’s going to take two or three weeks to fill the first million.  And they’re limiting you to 5 million per month.

If you have priority from the US government, let them know, and they’ll make sure US Customs doesn’t hold up your shipment.

And it’s a fair bet that these aren’t the only guys who were ready to go the instant the FDA backed off of its ban.

And, while those prices seem high to me, they don’t seem extraordinary.

For the time being, you, the consumer, should still refrain from buying them.  Leave them for the medical professionals.

But I expect the shortage to begin easing.  Better late than never.

What has me truly irked, of course, is how this dovetails with the CDC decision not to recommend masks in public.  If you think about it, if these two agencies had done this differently, there’s some chance that we could have all been wearing KN95 masks whenever we were out in public.  Or, maybe, all the people in New York City could have been wearing KN95s whenever they were in public.   Maybe it’s not too late to make that happen.  Bet that would have altered the course of this some.

Now more than ever. it’s time to keep reverse Roemer’s Law in mind:  A bed not filled is a bed not built.

If not for the inertia of the CDC and the FDA.

Just passing this along FWIW.  If you know somebody who needs a few million masks, email me, I’ll forward that offer to them.  chogan@directresearch.com

Post #597: Payroll protection program, pass this along please.

Below is an email I received from Zimmer Biomet, a company I used to consult for.  I hope that they don’t mind if I share it, but I am not going to bother them, at present, to ask permission.

It’s a nice, succinct description of the Payroll Protection Program.  If you know a small business owner, you might want to pass this on to them.  Today is the first day on which they may apply for aid under this program.

The key phrase here is this:  “The PPP provides an opportunity for certain small businesses to receive monies in the form of a grant instead of a loan (subject to certain conditions).”  Grant means you don’t have to pay it back.

That’s all I have to say.  All credit to Zimmer Biomet for putting this together in an effort to help support their suppliers.  Here’s what they sent me:


Coronavirus Aid, Relief and Economic Security (CARES) Act

President Trump signed into law a stimulus package which includes the Payroll Protection Program (PPP) authorizing up to $349 billion to provide small businesses with the capital they need.  The PPP provides an opportunity for certain small businesses to receive monies in the form of a grant instead of a loan (subject to certain conditions).   I have attached an overview together with a short summary (below, with hyperlinks) that I encourage you to review to understand the PPP.  If you are interested in this program, I encourage you to look into this as soon as possible with your accountants, financial advisors and others to determine if in fact you would qualify.  There will no doubt be a lot of interest in this program (as well as others) so we strongly encourage you to gather the needed information sooner rather than later so you can timely submit an application (as appropriate).

Recently, the Treasury Department issued more details on this paycheck protection program and a loan application available for download.

 

Where can I apply for the Paycheck Protection Program?

You can apply for the Paycheck Protection Program (PPP) at any lending institution that is approved to participate in the program through the existing U.S. Small Business Administration (SBA) 7(a) lending program and additional lenders approved by the Department of Treasury. This could be the bank you already use, or a nearby bank. There are thousands of banks that already participate in the SBA’s lending programs, including numerous community banks. You do not have to visit any government institution to apply for the program. You can call your bank or find SBA-approved lenders in your area through SBA’s online Lender Match tool. You can call your local Small Business Development Center or Women’s Business Center and they will provide free assistance and guide you to lenders.

Timing:

Banks and other lending institutions are mobilizing now. Starting April 3, 2020, small businesses and sole proprietorships can apply. Starting April 10, 2020, independent contractors and self-employed individuals can apply.  We encourage you to apply as quickly as you can because there is a funding cap

 

A Spanish language version of the guide is at: https://www.uschamber.com/sites/default/files/coronavirus_aid_spanish_3.31.20.pdf

 

Refundable tax credits

The Treasury Department and the Internal Revenue Service released a set of frequently asked questions (FAQs) today that provide additional information to small- and mid-sized employers on refundable tax credits that reimburse them for the cost of providing paid sick and family leave to their workers as a result of the coronavirus.  The Families First Coronavirus Response Act (FFCRA) enacted on March 18 gives businesses with fewer than 500 employees funds to provide employees with paid sick leave and family and medical leave related to COVID-19.

The FAQs are available online at: https://www.irs.gov/newsroom/covid-19-related-tax-credits-for-required-paid-leave-provided-by-small-and-midsize-businesses-faqs

A Treasury news release follows.  It also is available online at:  https://home.treasury.gov/news/press-releases/sm965

Treasury and IRS Release FAQs to Help Small and Midsize Businesses Navigate Paid Sick and Family Leave Tax Credits

 

April 1, 2020

 WASHINGTON – The U.S. Department of the Treasury and the Internal Revenue Service are offering small and mid-size employers more information on refundable tax credits that reimburse them, dollar-for-dollar, for the cost of providing their employees paid sick and family leave wages related to COVID-19.

“The financial strain American businesses are experiencing is not their fault,” said Secretary Steven T. Mnuchin. “These tax credits for small and mid-size businesses will cover the cost of providing paid sick and family leave wages, which will help protect the health of American families and businesses during this unprecedented time.”

The Families First Coronavirus Response Act (FFCRA), signed by President Trump on March 18, 2020, gives businesses with fewer than 500 employees funds to provide employees with paid sick leave and family and medical leave related to COVID-19.

Eligible employers can receive a credit in the full amount of the qualified sick leave and family leave wages paid for between April 1, 2020, and December 31, 2020. 

Employers can be reimbursed immediately by reducing their federal employment tax deposits.  If there are insufficient federal employment taxes to cover the amount of the credits, employers may request an accelerated payment from the IRS.

 

Read more information on small and mid-size business tax credits for paid sick and family leave.  https://www.irs.gov/newsroom/covid-19-related-tax-credits-for-required-paid-leave-provided-by-small-and-midsize-businesses-faqs

Post #___: Expedient masks, part 4: My niche.

Source: 3M

You can find numerous plans for sewing a mask. I’ll present one below, from Instructables, that I like for its simplicity and efficiency.  And for the fact that I see that other like-minded people also point to that design.

And I do, in fact sew.  I own a sewing machine.  And I do … big stuff:  slip covers, drapes, and so on.

Which, if you really know sewing, gives away the fact that I’m not good at it.  I could not set a zipper if my life depended on it.  I think Velcro (R) is God’s gift to  mankind the ham-handed.

And I now am hearing that a lot of people that don’t sew.  Doesn’t surprise me, really.  But we have an army of unemployed people.  So I’m making it my mission to help the sewing-challenged.

This is America, folks.  Think Apollo 13.  Have you never asked yourself, why in the world did NASA sent a roll of duct tape to the moon?  Can you even conceive of what it cost to do that?  And they planned on bringing it back?  They can eject an entire Saturn V first stage to self-destruct in the atmosphere, but the friggin’ duct tape had do be able to make the entire round trip?  Do you have any notion of what it takes to get a pound of material to the moon and back?  (Let alone a kilogram, which is why America had the best space program, right?)

I digress.  Got duct tape?

My role for the next few days is to put together a few high-protection masks, for the maskless, with minimal sewing.  Duct tape, 3M products, furnace filters, and such like.  Because, if you’ve been around, you know that if it’s 3M, it does what it says it does.  May not be the cheapest, but clearly the best.  This is no time to screw around with generics.

So this is the mask blog for rednecks.  Or maybe old rednecks.  If you don’t sew, but still occasionally refer to the big hardware store at Fairfax Circle as Hechinger’s, you’ve probably found the right place.

If mainstream America has the comfy fabric-store masks, what you’re going to get here is your basic hardware-store mask.  I aspire to channel Hyneman and Savage for the next couple of days.  WWMG What would MacGyver do.

But with the serious and ultimate goal of producing an N95-equivalent mask. 

Trust me, if you want comfortable masks, go with something that somebody sews.  So this may or may not be the most effective source for mask plans.  The best mask is the one that you’ll wear.

But if you’re among the paranoid — and, seriously, that’s hard even to define these days — even the most nervous of nervous Nellies would accept an N95-equivalent. Even if it’s ugly, and really not a lot of fun to wear.  And maybe then they’d leave the real ones for the pros who need them.

So I’m going to do non-sewn masks.  That’s what I see as the unfilled market niche.  These will not be as comfortable as sewn cloth masks.  They are going to be every bit as much of a pain in the … face as real masks.  But they are going to be a lot more scientific.

Tomorrow’s task is to replicate a 3M 8511 mask, from MERV-rated cloth and … not sure what else.

Got any good ideas, within what I have outlined above?  Email me:  chogan@directresearch.com

Post script:

Here’s what I believe to be the best sewn mask I’ve come across so far.  FWIW.  When I saw another MERV-mask maker mention this, I knew it was the right design.  Note that she has a design with a pocket for a filter.  So, if you have a high MERV filter at home, you could plausibly get the best of both worlds with this.  I find this an admirable design due to its simplicity, depth of face coverage, and attention to critical details like the nosepiece.  If you don’t have elastic at hand, think something like kitchen cotton twine would probably work.

Source:  Image used without permission, for which I apologize.

  • Mask 2:  DIY Cloth Face Mask.  By
  • Cloth:  Tightly woven cotton or cotton/poly.  Cotton recommended.
  • Layers:  2
  • Ties:  Elastic, over ears.
  • Metal noisepiece:  Yes, continuous wire, sewn in, floral wire or other thin wire.
  • Design:  Single piece of cloth with elastic feed through “drawstring”-type channels at side.
  • Methods/skill level:  Knowledgeable craft sewer.
  • Steps:  14
  • Number made:  73
  • Interesting quote:  “Surgical masks and some cloth masks will block 7 micron particles.”

Post #595: Expedient masks, part 3: Expedient mask prototype

Rapid conversion of dust masks to MERV-8, proof of concept.

 

I just heard that the Mayor of Los Angeles has asked everyone to wear masks in public.  So, now more than ever, we need effective masks for everyone.  I reviewed what’s for sale, and a) it ain’t much, and b) likely, most of it is gone by now.

Just breaking:  Looks like the CDC is finally going to issue guidance to wear masks in public.  Thank goodness.  I’ve just been told that Laredo, Texas will now fine people for being in public without a face covering.

Maybe the Army Corps of Engineers can produce and distribute a few optimized mask designs, with the idea that its within their mandate as sort of reverse Roemer’s Law.  A bed not filled is a bed not built.


In Post # 593, I showed the key tables from a scholarly article on home-made respiratory masks.  That analysis looked at the air-filtering properties of various types of cloth.  And, in fact, you could achieve particle filtration equivalent to a surgical mask, merely by using two layers of tightly-woven a tea towel.  But that two-tea-towel mask would have generated much higher back-pressure than a surgical mask (i.e., hard to move air through it).  That would have resulted in moving a lot of air around the mask (at the edges), rather than through the mask.  So, likely, you’d end up inhaling significant amounts of unfiltered air.

Return to Post #593 for the discussion MERV standards for air filters.  There was a reason I included that.  Some people (and other people) (and even some doctors) (and some nurses) have already come to the conclusion that the obvious material for home-made masks is the fabric inside of furnace air filters.

At the end of this, I’m going to make something that I think is obvious.  Take a dust mask — one with no guarantee of filtration at all — and tape a piece of MERV-8 cloth over it.  That should provide excellent protection against droplet transmission.  The shape of the face seal is formed by the factory-made dust mask, and is far better than I could achieve by hand.  The filtration is performed by the MERV-8 material, which should be adequate for droplet protection.  It uses a minimal amount of the MERV material.  I believe I could get this down to maybe — well certainly under 5 minutes a mask.  And if I can swap out MERV-16 for MERV-8 and still breathe through it, the same techniques would allow me to mass-produce N95-equivalent masks.

Seriously, I think this is a way to help solve America’s current shortage of masks for the public.  So this is my last plea:  If you know someone in a position of responsibility, please pass this along.  Because this way, not only do you have a mask that protects others.  This way, if I up the MERV level, you have a mask that protects you.  Using filtering materials that are outside the hospital supply chain. 

And if you can suggest ways to do this better, or have an idea for a better design using MERV-rated furnace filters, email me (chogan@directresearch.com).

Let me now list the advantages of the MERV-based mask.

  1. It has a known level of filtration, the MERV rating.  With cloth, you have to guess.
  2. You can achieve a N95 level of filtration with a (rare) MERV-16 filter.  This would provide protection against aerosol (airborne) transmission.
  3. You can filter out some small droplets with a MERV-8 or higher.  This would provide protection against droplet transmission.  You can get almost all of them with a MERV-13 or so.
  4. Most American homes have some supply of these in the basement, so there is a large supply of this material readily available and already distributed to homes.
  5. The only tool required to extract the cloth from filters and work it into shape is a set of common household shears.
  6. The MERV-8 cloth is easy to work with (well, sort of), if somewhat fragile.
  7. FWIW, except for Filtrete (R) filters, I believe that the material in MERV-rated furnace filters is in fact melt-blown cloth, the same stuff that is in masks.

And so, while I could talk about how to sew a cloth mask, for that, I think I’ll just just put that off, for the time being.  At some point, that will come back into play, because I would need sewn bodies for my MERV-based masks.  But for now, let me just convert a dust mask that I have, and see how that works out.

I’m not even going to review MERV.  Refer back to Post #593 if you want to brush up on it.  For now, you’ll just have to take me at my word that MERV-16 requires 95% removal of particles down to 0.3 microns, in one pass.  Just line N95.  And we can work backwards from there.

For the record, I know MERV-8 ain’t great.  You can see the specs here.  But its what I happen to have.  MERV-8 only guarantees to trap 70% of particles between 3 and 10 microns in size.  And only 20% of those those 1 to 3 microns.  (Aerosols are those 5 microns and below).  But a MIRV-12 — readily available for home use, traps a minimum 90% and 80%, respectively.  And, you can double up the fabric, get two passes, and presumably raise those to something like 99% and 96%, respectively.

(And MERV-16 is basically the same spec as N95:  It gets 95% of particles down to 0.3 microns.  But I just got my hands on a MERV-16 filter, and I don’t think I could breathe through the material..)

So this is a proof of concept.  I.e., I’m wrecking a relatively low-valued MERV-8 filter.  Once I’ve fine-tuned this, I’ll move up the MERV scale.


Section 1:  Converting a MERV-8 pleated filter, and common dust mask, to a MERV-8 mask.

You’re going to take a standard home air filter, MERV-8, cut it out of its casing, leave the wire backing in place, cut out a rectangle, mold it around a common dust mask, trim and tape in place overtop the dust mask.  Then replace the elastic with something more substantial.

Tools and materials:

  1. MERV-8 or better home air filter
  2. Kitchen shears, large scissors or similar
  3. Sharp razor blade (optional)
  4. Packing tape, duct tape, Gorilla (R) tape, or similar.
  5. Piece of cord (shoelace, parachute cord, kitchen twine, garden twine).

1  Remove the filter from the cardboard casing, taking care not to damage the fabric.

You can’t peel them out without damaging them.  I learned that the hard way.  Take a pair of scissors and cut them out, cutting right through the metal mesh on the back.

On mine, the carboard on the face was randomly glued to the fabric.  Don’t pull that off.  For now, just cut around it, leaving chunks of cardboard on the fabric surface.  You can cut them down later, and either leave them or carefully get them off the fabric with a sharp razor blade.

Step 2:  Roughly flatten the fabric and wire assembly.

Leave the wire mesh attached.  I tried removing the fabric from the wire, but a) it was tedious and b) being as careful as I could be, I was still damaging the fabric.  I would prefer to work with the fabric alone, but that’s not gonna happen.

Step 3:  Cut roughly to size.

Carefully roll the mask in one direction, mark, then roll it in the other dirction, and mark.  Give yourself maybe a half-inch seam allowance all the way around.

Step 4:  Roughly shape the filter material by wrapping it round one fist.

Check for fit against the mask shape.  Fine-tune as needed.   Avoid creating “folds” in the material, to the extent possible.  I have a large fold at the bridge of the nose that may, to small degree, compromise the filtering, but … when I look at it, it’s not obvious that it does.

Once you are comfortable with the fit, trim the excess.  It’s OK to be a bit sloppy because you’re going to cover the joint between the two materials with plastic tape in the next step.

Step 5:  Attach the filter material to the dust mask.

Lay down a ring of tape on the mask seal.  This is just small pieces of high-quality tape.  It’s important that these overlap a bit, because these are going to become, in effect, the new mask seal.

Lay the dust mask into the shaped filter/mesh assembly, start in one place, and tape it all around.  When you are done, take a couple of strips of tape about 1″ wide, and just tape your way around the circumference of the mask.  Just to stabilize it, and make sure it sticks.

Step 5:  Replace the elastic with a cord of some sort.

Knot the cord, tape it to the mask.

6:  Put it on on, bend to adjust fit as necessary, and tie tightly.

Time and materials summary:

This entire process took me an hour, and left me with enough MIRV-8 material to make, looks like, maybe another 7 or 8 masks, with a lot of waste (because the mask min dimension is just over half the MERV-8 sheet that I got from my 14 x 30 x 1 filters.

Performance:  Yeah, it works.

I’ve been wearing this for an hour now, and it’s hot, uncomfortable, and it stinks a bit of plastic..  Which is to say, behaves like just about every other face mask.

I was worried that I would compromise the mask seal, but I don’t think I did.  For one thing, my glasses aren’t fogging up.  I don’t notice any leaks with a wet finger held near the edge (and sharp exhalations).  And, when I exhale, I can feel my hot breath diffuse out the lower part of the mask.  I want it going through the mask, not around the mask.

Back pressure is fine.  Not at all hard to breath, despite narrowing the breathable area somewhat with the plastic tape  .As it should.

The plastic tape is a little itchy, and I can feel a couple of the seams.  But I actually think the plastic tape, the overall metal mesh, and heavy-duty tie, in total, results in a pretty good seal against my face.

Tomorrow I’m going to review what other MERV masks are out there, and either improve this one, or build one of a different design.

And keep in mind, there is no obvious barrier to do this with MIRV-16 material.  The only real hitch there is that few domestic furnaces or air cleaners use MIRV-16.  And MIRV-16 — at least in terms of the specification — matches N95 for capture of 0.3 micro particles, and such.

I, Christopher Hogan, PhD., place this posting entirely in the public domain.

 

Post #594: Expedient masks, part 2: What can you buy

Source:  Amazon.com


As our Federal government stumbles toward a public mask policy at a glacial pace and with off-the-cuff advice, let’s see if we, the people, can get ahead of the game on this one.

The just-prior post already established that a reasonable home-made mask will do just fine for protecting others.  This next series of posts is about protecting yourself.  

And this post is about what you can buy, right now.  Its about expedient masks, meaning anything you can buy or make to serve as a face mask, that would (we hope) never be used by health care workers.  Anything other than real medical masks — either N95 (or equivalent hardware-store P95) or proper, certified surgical masks — such as might be used in a hospital.

Upshot:

If you want to buy a plausibly-effective sanitary mask, right now, for wearing in public, it looks like your sole option is disposable “surgical” masks bought through Ebay.  As discussed below, these are not actually proper certified surgical masks, and some of them are in fact simple “single-use” masks, as described in my just-prior post.  You can order the same thing through Amazon, but typical wait times are about a month.  I list out the features you want to see in those masks, if you buy them, below.

Caveat emptor:  I just looked at Ebay, and there are clearly a lot of unscrupulous sellers, and a general air of on-line panic shopping.  If you absolutely have a need for these, consider it.  But be aware that you may well be wasting your money.

In addition, anybody who is in the business of throwing away N95 or P95 masks (respirators) should read this analysis of how long an N95 may be re-used.  The answer is, putting aside the issue of sterilization, a long, long time.  Which is good, because (e.g.) the screeners at Dulles Airport have been asked to re-use their masks on a permanent basis.  So, even if you don’t re-use them now, it’s probably time to start separating them from the rest of the waste stream and retaining them.


What’s off-limits, what’s available on Amazon

This post is about masks that you can buy, right now.  And, separately, how you might modify them to improve their filtration capabilities.  I’m not going to spend a lot of time on this, because I suspect that when CDC issues guidance that Americans should wear masks when in public, anything for sale will disappear from the shelves.

I am sticking with Amazon, for the time being, because they appear to be doing things responsibly, as discussed below.  As I read it, right now, if you see it for sale to the general public on Amazon, that’s because it’s not needed by the US health care system.  That is not uniformly true of places like Ebay.  So I’m only going to look at items that are for sale on Amazon.  I may check availability of those same items on Ebay.  Clear enough?

I spent some time explaining the technical jargon in the last post, so I am going to feel free to use those terms around here without explanation.  Just refer the last post.

But this is not about protecting yourself, at the expense of the health-care workers.  In my last post, I explained why hospital workers need N95 masks and you don’t, under the section on aerosol transmission of disease.  So let me list not just the things you can buy, but the things you shouldn’t buy.


N95, P95, P99, P100:  NO. 

Source:  Wikipedia

If you stumble across anything rated N95 or P95 or better, just leave it alone, unless you plan to purchase it for donation to your local hospital or fire and rescue unit.  You should not be able to find these for sale now, but that’s only because responsible companies have withdrawn them.  (See Home Depot in just-prior post.  I don’t think the Federal government has taken any action to make the sale of these (to other than medical/fire/rescue providers) illegal. This class includes not only classic N95 “masks” as above, but (e.g.) anything like the P100 paint respirator pictured at the very top of this posting.

Again, you don’t need it.  Health care workers and fire and rescue units are going to need them.  See my prior post on why health care workers need them, and you don’t.


Surgical masks certified for medical use:  NO.

Source:  Wikipedia.

I’m not sure if you can find proper certified surgical masks for sale or not, but ditto the remarks above on N95s.  Leave them for health care workers.  Please see the prior post for a discussion of the difference between single-use masks and surgical masks, and the filtration standards.

Note that several large-scale controlled clinical trials show that surgical masks are just as good as N95 respirators at preventing flu infection among hospital workers.  An excellent summary is here, at Smart Air.  So, in a pinch, you bet hospital workers would use those if N95 respirators are not available.

Read my just-prior post for the difference between certified surgical masks, and “single-use” masks, which you can buy, and which are not critical to the US health care system right now.


Things that look like surgical masks but are not certified for medical use, available on Amazon, and are probably “single-use masks”, not surgical masks (defined below):  I would say, yeah, for now, probably YES. 

Wait times are long (typically one month) on Amazon, but this same sort of produce appears widely available (for now) on Ebay with short delivery times promised.

Source:  Amazon

What makes me say that?  Amazon is one of the responsible vendors who have pulled all masks that can be used by medical personnel and first responders.  Anything like that, their pages now have this wording:

Available only for hospitals and government agencies directly responding to COVID-19

For example, Amazon has withdrawn not only N95 respirators, but high-quality nuisance dust masks as well.  They have withdrawn surgical masks that appear to be certified for medical use.  (Note that those masks list their actual filtration rates, whereas the ones that remain for sale do not.)  To me, that suggests that they really have gone through their inventory and pulled out anything that would be useful to medical providers or first responders.

I have to infer, then, that if Amazon doesn’t say that, then there has been some professional judgment that the item in question is not needed by health care workers.  I am not 100% sure about that, but at some point, I have to believe that Amazon knows its business, and has done the right thing, and has stopped sale of all items that would be useful to health care workers (as Home Depot has done.)

An incredibly helpful and succinct discussion of single-use masks, surgical masks, and N95 respirators, along with considerable other helpful information (e.g., can you wash disposable masks) can be found at Smart Air.  If you want to get up to speed on what’s what, for actual medical supplies, that’s the place to start.

So, provisionally, I’m going to say, despite some misgivings, these are probably OK to buy.  I’m guessing that most of them are, in fact, “single-use masks” and not surgical masks.  If (note, if) those were manufactured to any standard, it would be a Chinese standard, and they would be able to filter out 95% of large aerosol droplets (3 microns), but would not filter something the size of a virus.  Proper surgical masks, by contrast, will filter out virus-sized particles.  Again, see Smart Air for a discussion of mask standards.

Even though these are not certified, and some appear to be poorly made, many of them do appear to have the right construction:

  • Three-ply construction, with
  • A layer of melt-blown fabric, and
  • A metal strip at the bridge of the nose.

To the extent that these are fairly good at filtering the air, that’s due to the melt-blown fabric and the nose piece.  See prior post for “melt-blown fabric”.  (You don’t know the quality/specs on the melt-blown fabric, but at least it has some, suggesting that it has filtering ability above-and-beyond what you’d get from just paper.) The nose piece is required to seal up what would otherwise be the largest air leak for the mask, right at the bridge of the nose.

Finally, multiple large-scale controlled clinical trials have shown that proper, certified surgical masks (not single-use masks) work just as well as N95 respirators at keeping hospital workers from catching the flu.  (Cite Smart Air). Whether or not whatever-these-are on Amazon — single-use masks or possibly uncertified surgical masks — would work as well as certified surgical masks is a complete unknown.  For sure, single-layer single-use masks, even if they were built to the Chinese standard, have no ability to filter virus-sized particles.  They would not have the filtration capacity of a certified surgical mask.

Check the delivery time before you buy.   The main catch here is delivery time.  That nice-looking white mask above?  I searched “face mask”, sorted by descending customer rating, and checked the earliest promised delivery time for the first 20 entries.  Median earliest promised delivery date was 26 days.  Three entries promised delivery within six days.  Two of those were of such low quality (by description and customer comments) that I doubt they would work.  The third was priced at about three times the going rate for masks.

The upshot on delivery is that a) for the typical product, it’s going to take a month, and b) anything promised for near-term delivery is either too poor to be useful, or (in one case) priced at several multiples of the going rate.

I re-sorted by descending price, and spot checked.  Even for very large orders (e.g., 1000 masks) first promised delivery dates were about a month away.

To summarize:  It appears that Amazon has stopped selling anything that has been judged useful to the medical or first-response sectors.  The only safe thing is to assume that whatever you are seeing on Amazon, at best, meets the Chinese standard for filtration for single-use masks.  If so, those would provide significant filtration against droplets, but limited filtration against aerosols and virus particles.  (I.e., they aren’t as good as real surgical masks).  Some of the disposable masks appear to have proper construction, per bullet points above.  If so, you could reasonably assume that wearing them would offer you some protection, but that is just an assumption.  The best of these have melt-blown fabric (the “filter” portion of a certified surgical mask), but you have no way of knowing what type of melt-blown fabric it is (i.e., how well it would filter air).  Even with that, you should expect about a one-month wait time for anything that looks worth buying, or feed the occasional price gouger who is promising an earlier delivery time.

Can you get them now, on Ebay?  Yes, that appears to be true.  If you go that route, look for three-ply construction, metal nosepiece, melt-blown fabric, and some claim as to bacterial filtration.  You have no idea whether the claim is right or not, but so be it.  A fair price appears to be in the range of $0.70/mask or so, in large lots.


Fabric sports masks:  YES, if you are wiling to modify it.  What you can routinely get does not appear very effective as a protective mask, because these are designed to “breathe”.  If you can sew, you can add a lining.  If not, you can try to add a paper lining.  You will definitely want to add a wire nosepiece to provide a tight fit across the bridge of the nose.

Source:  Amazon

At present, everybody says that any type of fabric mask is OK. Masks like that are frequently sold as pollen/pollution masks for outdoor exercise.  Amazon has a wide range of them. Most (perhaps all) are really not adequate for this task, consisting of a single layer of cloth.  Because these are exercise masks, they are made to “breathe”, which is what you don’t want, right now.

At the minimum, you’d have to line these with something.  Practically speaking, I think you’d have to resort to lining these with paper towels.  That provides some protection, but not much (see prior post, last section).  You would also want to take a bit of wire and either duct-tape it to the mask, or thread it through the mask, to provide a metal nosepiece for sealing the mask to your face at the bridge of your nose.

And, as with the disposable masks above, most have one-to-two-month shipping times.  I saw a handful with promised delivery times of a couple of weeks.  Weirdly, I did not find these on Ebay.  Maybe I just didn’t have the right search terms.

I’m not going to pursue these any further.


“PM2.5 masks”:  Eh, I’m not even sure what this means.

Source:  Amazon

There is a huge range of masks — some hard-surfaced, as the one above, some fabric, some hybrid — that are sold as anti-air-pollution masks.  That is, they claim to filter out particulate matter of 2.5 microns in size (PM 2.5).

Near as I can tell, as discussed in my prior post, there are no standards and there is no testing of these masks.  Some probably work.  Some probably don’t.  I have no way to tell.  I’m not going to discuss these further.  The few that I checked appeared to have delivery days 6 weeks away or so.

Caveat emptor.


Various loose-fitting masks and bandanas.  These protect others, a bit, but the lack of any seal means they provide very limited protection to you.

Source:  Amazon

And, of course, even these have promised delivery dates 6 weeks out.  These are single-layer loose-fitting cloth mouth coverings.  Better than nothing, but probably not as good as just pulling your t-shirt up so it covers you nose and mouth.  I don’t see value here.


Etsy hand-sewn cloth masks.

I did not pursue this option, but I would assume that some are available.


My next posts will discuss making masks.


Post #593: Expedient masks, part 1, background.

Source:  Amazon.com

 

The bottom line of this posting is that, yes, home made masks work to block much of your potential for transmitting disease to others.  Wear a real medical mask if you own one.  Buy (and potentially improve) a non-medical one if you don’t.  Or make one from scratch.  Even paper towels have some efficacy in filtering the air.

This post is really just background.  If you already know that you need to wear a mask, there is no need to read this.  Next post will be about what you can still buy, for now.  Final post will be on making them.


Background

The drumbeat in favor of universal mask use outside the home is getting louder. Some people figured this out sooner than others.  I finally wised up less than a week ago, and did my 3/27/2020 grocery shopping masked.  And every time I enter a public place from now on, I’m wearing a mask.

That said, you can see a summary of the achingly slow progress on this front in this Washington Post article.

So, unless spectacular stupidity triumphs, you will soon have official guidance from the CDC that you ought to wear a mask in public.  I’ve already written down what I would use as the official rules, FWIW (Post #589).  I’ve now posted a comment on the Whole Foods Facebook page, asking them to consider some form of “no mask, no service” policy.

Everybody who is smart, ethical, or both is withholding N95 respirators from the general public.  AKA, the best masks.  Those need to be kept for health care providers.   Here’s Home Depot’s policy.

Executed a "Stop-Sale" on all N95 masks in stores and HomeDepot.com and redirected all shipments to be donated to hospitals, healthcare providers and first responders around the country

I highlight Home Depot because that’s the first place I detected panic buying/hoarding behavior, back in Post #535. Even if they were too late to stop that, they have had the good sense not to restock.

My point is that mask use is coming.  You can’t buy the ones that protect you with some security (if they are properly fitted).  What can you do?  What are your options for an expedient mask?  What is your best expedient mask choice?  Adapt what you have?  Buy?  Buy and modify?  Make from scratch?

From the standpoint of not infecting others, it’s all good, pretty much.  Any mask beats no mask, hands down.  When you talk, and even to a small extent when you breath, you emit tiny droplets (discussed at length in Post #573, Post #585). Droplet transmission of disease is believed to be the primary way in which the infection is spread.  Any sort of substantial cloth barrier over your face will reduce the spread of those droplets significantly, both by catching some, and by reducing the velocity/range of others, as the mask slows the velocity of your breath.  (See wet finger whistle test in Post #589 to prove this to yourself.)

See this reference for a scholarly look at the ability of home-made masks to stop spread of disease.  But please note that they used the wrong cloth (cotton t-shirts) — nobody recommends that.  They concluded that homemade masks aren’t as good as surgical masks, but they are much better than nothing.  I’ll get into that paper in detail, at the end of this posting.

So the only thing to discuss, really, is how you can get some sort of mask, and then, how well can you expect that mask to protect you.  This assumes you are smart enough to do everything the CDC already says, and in addition, minimize your trips to enclosed public spaces, and the time you spend there, on those trips.

While you can buy some type of (e.g.) cloth face mask now, well, by this time we all know the drill.  The supply chain is set up to deliver product only at the rate at which it is used.  As soon as the CDC says “wear a mask of any sort”, it’s a fair bet that what’s currently for sale will get hoovered up.

So, for most of you who don’t have a mask, I’m afraid this is going to turn into a DIY project.  Or, having your neighbors make one for you.

So I thought that what I might do is offer a kind of mask tutorial.  This is mostly by way of helping me get my thoughts together on whether or not I could build a high-quality expedient mask from available materials.  Anybody can make a mask.  The question is, can I make a good mask, in quantity.

This is part 1:  Background.  Part 2 will be, what can you buy (for now) and modify.  Part 3 will be, what can you make from scratch.


Step1:  What are we talking about?  Definition of N95, PM2.5, MERV, HEPA, and so on.

I’m kind of tired of writing, at this point, so this will largely be done without citation as to sources.  I’m just summarizing things here that I have duly cited in earlier posts, mostly. New information will be cited as needed.

Aerosol versus droplet transmission

Micron (micrometer):  One millionth of a meter.  1000 nanometers.  Droplets from a sneeze range from under about one micron to hundreds of microns.

Nanometer: One billionth of a meter. The diameter of an individual coronavirus particle is around 120 nanometers (Wikipedia).  An obsolete term for it is “millimicron” or “millimicrometer”.

Aerosol versus droplet transmission.  Here’s a key distinction.  Conventionally, anything under 5 microns is an “aerosol”, meaning, it will stay suspended in the air and float around on air currents.  See Post #585.  Particles that size are far too small to be seen. When professionals talk about “airborne transmission”, then mean transmission of the disease in this fashion. If you inhale enough of them, from an infected person, and they land in the right place in your respiratory tract, you get infected.

Studies of influenza showed that aerosol particles were quite potent at spreading lower respiratory tract infections.  It takes less total volume of virus to cause an inflection of you aerosolize it, versus leaving it in larger droplets.  The reason is that if you inhale these tiny droplets, they have the ability to penetrate far into the lungs.  (This same ability is what makes very fine particulates from (say) diesel exhaust particularly harmful air pollution).  And, for SARS (currently SARS-CoV-2 aka COVID-19), that’s where this virus wants to be.  So aerosols put the virus directly into its most favorable habitat within the human body.

Sneezing and coughing produce some aerosol-sized droplets.  But, surprising, just breathing produces a few.  Talking produces them at a rate somewhat less than coughing (but you talk a lot more than you cough, so total production can easily be the same, when integrated over time).  The louder you talk, the more aerosols you produce.  And singing is easily the equivalent of coughing, in terms of the rate of aerosol production.

One fact you need to know is that, for aerosols, some people are “superemitters”.  They produce orders-of-magnitude more aerosol than the average person.  And it’s not really all that rare, but I’m not going to stop and look that up right now.  My recollection is that in any group of 100, you are more than likely to find a few.

And so, likely that event that I wrote about — 45 persons of a 60 person choir got COVID-19, after a single carefully-done practice — it’s a very good guess that this was the result of aerosol transmission of disease by an infected superemitter.

That said, I need to be clear here, because this is now a hot topic:  As far as anyone knows, aerosol transmission of this disease is rare outside the hospital setting.  How do they know?  Well, they think they know that because of what they think they know of the epidemiology of it. If aerosol transmission were common, you probably wouldn’t be able to trace cases back and figure out how they got infected.  Because they think they can do that tracing, and they find that most transmission (that they can trace) appears to occur when people are symptomatic (i.e., coughing), they infer that most transmission is, in fact, droplet transmission, not aerosol.

Let us each now solemnly pray to our respective God or Gods that they are correct, and not just kidding themselves.

The situation in a hospital is different, though.  There, you can get instances where the concentration of aerosol particles is high enough, and exposure times are long enough, that people can get sick literally by simply breathing the same air as the patient.  You’ve got a combination of a very sick patient (so, high virus shedding rate), in a small room (so that person can build up high density of aerosol per cubic foot), and you have health care personnel who spend considerable time in that tainted air.

The non-negligible potential for aerosol transmission in that setting is one of the reasons that health care practitioners need N95 masks.  I’ll get to the definition of N95 below.

By contrast, health professionals use the term “droplets” to mean drops larger than 5 microns.  To a greater or lesser degree, these settle out of the atmosphere fairly quickly.  (Or, at least, that’s the conventional wisdom).  But, if you inhale them, or they land on you in the right place (in your mouth, eyes, nose), or they land on a surface that you touch and then touch your face (mouth, eyes, nose), they can infect you.

You produce droplets by sneezing or coughing, but you also produce them by talking.  (And, because we talk a lot more than we cough, arguably, at small droplet sizes, we’re producing more in total by talking.  Which is among the reasons I called for us all to shut up in public spaces.)

The fact that droplets settle pretty quickly is the basis for the 6-foot social distancing rule.  In theory, if somebody coughs from six feet away, the droplets produced won’t hit you.

But social distancing alone is not good enough for the Chinese.  They use masks, both to absorb some of the droplets, and to slow down the velocity with which they are projected away from the source.  And they are absolutely right in doing that.  Which is why US policy is about to change.

Filtration standards and such.

An incredibly helpful and succinct discussion of single-use masks, surgical masks, and N95 respirators, along with considerable other helpful information (e.g., can you wash disposable masks) can be found at Smart Air.  If you want to get up to speed on what’s what, for actual medical supplies, that’s the place to start.

A different guide to the different types of “surgical” masks can be found at Crosstex (.pdf).  The takeaway  from both of these is that just because it looks like a surgical mask does not mean that it filters viruses and droplets like surgical mask.  It may or may not.  And if it were certified to filter like a surgical mask, it would probably not be on sale to the general public.

N95:  A filtration standard meaning that, when new and carefully tested, a mask will stop 95% of very tiny (0.3 micron or 300 nanometer) particles.  Source:  FDA.  Note that, in real life, you don’t actually achieve that because air leaks around the edge of the mask.  That’s why, for protecting the mask user, a properly-fitted mask is important.  For the mask maker, that means you need to construct it so it seals well.

But that’s the primary reason that health care professionals need N95s.  They really need to be able to stop everything, all the droplet sizes, and stop particles down the size of a few viruses stuck together.  That’s why they need those masks more than we do.

N99, P95, P99:  Additional mask standards.  First one filters 99% of particles that size.  The Ps have the indicated filtration, but are good for oily particles as well, where the Ns aren’t (I think of it as P as in paint).

How in the heck do you filter out something that small, and still be able to breathe through the mask?  Mainly, through the miracle of Melt-blown cloth.  This is a nonwoven cloth made from small-diameter plastic fibers fused together.  It is the heart of most common medical masks, including both N95 and true surgical masks.  This is the element in the mask that filters out fine particles.  And, of course, many different types are made, so you can’t just buy melt-blown cloth and assume it’s good enough for a mask.

PM2.5 (particulate matter 2.5 microns) refers to air pollution particles of around 2.5 microns in size.  In essence, PM2.5 is shorthand for all the common air pollutants that are aerosols, i.e., can stay suspended in the air.  Note that, by definition, an N95 mask filters out at least 95% of PM2.5.

PM2.5 mask.  Near as I can tell, this is not a standard.  This just means that the manufacturer claims that the mask was designed to filter out PM2.5.  It’s a mask that claims to filter out (some, all, most?) particles of that size.   Near as I have been able to tell, a) nobody tests those claims, b) a lot of PM2.5 masks and respirators don’t do what they claim (but some do), and c) near as I can tell, these are not approved for use by health care personnel.

Mask versus respirator.  Near as I can tell, anything that is truly designed to seal up against your face, so that air doesn’t leak around the device, is technically a respirator. By contrast, if it’s designed that air likely leaks around the edges and/or the principal purpose of it is to stop fluids, that’s a mask.

That’s why you’ll hear the terms N95 respirator and N95 mask used interchangeably.  Even though the thing looks like a mask, it’s supposed to function like a respirator.  You are supposed to fit the thing to your face so that air leaks are minimized.  Otherwise, really, what’s the point?

Edit:  Single-use mask versus surgical mask.  I didn’t even realize there were standards here, but see this page at Smart Air for a very helpful discussion.  Single-use face masks are typical single-layer thin masks.  If manufactured to the Chinese standard, these will stop large droplets (3 micron) fairly well, but not viruses.  The US does not have a standard for these.  The US only had standards for surgical masks:

Surgical mask standards:  BFE and PFE.  An excellent summary of the difference between single-use masks, surgical masks, and respirators can be found at Smart Air Filters.  They explain it much better than I do.

Edit:  CORRECTION.  I have now located a proper description of surgical mask standards, from Primed, which I am going to crib here.

1. BFE (Bacterial Filtration Efficiency): BFE measures how well a surgical mask mask filters out an aerosol consisting of 3 micron droplets containing staph.  In order to be certified as a surgical mask, the cloth has to filter out 95% of those droplets.  Better grades of mask (mderate and high protection masks) must filter out at least 98% of those droplets.

2. PFE (Particulate Filtration Efficiency): PFE measures how well a mask filters out virus-sized particles.  They are supposed to be tested with particles of 0.1 micron size (about the size of coronavirus).  The higher the percentage, the better the mask filtration.  Apparently, some masks are tested with somewhat larger particles, and can show a misleadingly high PPE.

Note that the actual performance of a surgical mask, in use, will not be as good as these filtration rates suggest, because the mask does not seal up against the face.  (See Mask versus Respirator).  Air leakage around the edges of the mask compromises the overall filtration.  The standards above show the filtering ability of the cloth, not the overall mask assembly as a whole.

Edit: WRONG. Note that surgical masks are NOT tested for their ability to stop penetration by bacteria in the air.  They ARE tested against penetration by fluids, and penetration by bacteria and such in fluids.  They are designed for health care workers who need to avoid being infected by fluid-borne bacteria and viruses.  As far as I can tell, that’s why a proper surgical mask, tested and certified for health care use, has some ability to filter particles.   Most (some?) are made with three-ply construction, the middle ply of which is some form of melt-blown cloth.

And, helpfully, melt-blown cloth is also used in some (but by no means all) home furnace filters ( (see this manufacturer’s page)Which gives me the segue to comparing the standards above to two that homeowners are familiar with:  MERV and HEPA.  And here, I assume you all know I am not talking about standard fiberglass, very-open-weave filters.  I’m talking about the ones that look like a sheet of fuzzy cloth.

MERV:  Minimum Efficiency Reporting Value.  From Wikipedia.

The scale is designed to represent the worst-case performance of a filter when dealing with particles in the range of 0.3 to 10 micrometers. The MERV value is from 1 to 16. Higher MERV values correspond to a greater percentage of particles captured on each pass, with a MERV 16 filter capturing more than 95% of particles over the full range.  (That little factoid will be important for tomorrow’s post.)

Do two MERV 8s make a 16?  No, absolutely not.  The MERV rating is like a pore size.  As you go up the scale, in groups of four, they start filtering smaller particles.  The 8s simply have larger pores, in effect, and let the smallest particles pass through.  That’s clear from this full explanation of MERV ASHRAE chart.  (But, if I’m reading that right, two MERV 14s, in sequence, come very close to achieving the same filtration as a MERV 16.  And two MERV 15s in sequence exceed that).

HEPA:  High-efficiency particulate arresting.  Again, from Wikipedia:

“Filters meeting the HEPA standard must satisfy certain levels of efficiency. Common standards require that a HEPA air filter must remove—from the air that passes through—at least ..  99.97% (ASME, U.S. DOE)[5][6] of particles whose diameter is equal to 0.3 μm; with the filtration efficiency increasing for particle diameters both less than and greater than 0.3 μm.[7] 

The little μm thing is microns (micrometers).

MPR:  Microparticle Performance Rating.  This is a propriety rating system developed by 3M.  It reflects the ability of a filter to capture the smallest airborne particles—from 0.3 to 1 µm in size (Wikipedia).  So you have to get the detailed 3M literature, if you want to look at Filtrete electrostatic filters:  https://multimedia.3m.com/mws/media/1740587O/filtrete-merv-vs-mpr.pdf

Filtrete (r) filters differ from MERV-rated filters in that all varieties of Filtrete capture some small particles.  If you look at E1s (the smallest particles, down to 0.3 micron), it appears that you need two layers of MPR 2800 Filtrete to achieve 95% or more of filtration of E1 particles.  Although, for particles one micron and up, one layer of MPR 2800 or one layer of MPR 2500 would achieve 95% capture of those particles in a single pass.

I am uncertain as to how that Filtrete electrostatic material behaves under adverse conditions, such as when damp.


Filtration properties of common household materials. 

This is where the rubber hits the road.  Start with this article, where they actually tested cloth and made masks.

Here’s one key table, below

This is a pretty good setup, because they literally aerosolized the bacterium and virus, then tested what happened when they pushed that aerosol through a cloth panel at about the rate you would if you were breathing.  These particles are certainly on a par with the size of the coronavirus itself, and presumably the aerosol droplets are about the best proxy you are going to find for … well, aerosol droplets.

First, note the similarity of the first two columns, despite the differing size of the bacterium and the virus.  That’s because, by and large,  the masks are catching the droplets, not the individual bacteria and viruses themselves. The standard here is the surgical mask, circled in red.  I note that a vacuum cleaner bag (not stated as to type, likely not HEPA, because I’m pretty sure they are talking about cloth bags) was just about as good as a surgical mask — I put a red line there.  And a tea towel, doubled over, was just about as good.  But in the right-hand column, that’s the back-pressure you would face, in breathing through those materials.  The vacuum-cleaner bag and the doubled-over tea towel were 2 to 2.5 times harder to breathe through than the surgical mask material.

Source: Testing the efficacy of homemade masks: would they protect in an influenza pandemic? Davies A1, Thompson KA, Giri K, Kafatos G, Walker J, Bennett A.  Disaster Med Public Health Prep. 2013 Aug;7(4):413-8. doi: 10.1017/dmp.2013.43.

This is important, because the harder the material is to breathe through, the more air will leak around the mask, rather than through it, and reduce the overall filtration efficiency.

So, to be clear, yeah, you can find stuff around the home that will give as much filtration efficiency as a good surgical mask (but not an N95 mask).  But it’s going to be somewhat hard to breathe through.

And, if you care, read the section of that paper on fitting the mask.  All of the home-made masks were much leakier than a good-quality surgical mask.  That’s important, and that’s what you need to focus on if you make a mask.

Finally, how much better is it to wear a home-made mask, made out of a cotton t-shirt, than to have no mask at all, in terms of containing the spread of disease (from people coughing, in this case).  Well, they tested that empirically:  Literally had people cough, through a mask, into a sterile box, and counted the crap that came out.

 

Source:  Same as prior table.

Do home-made masks help prevent the spread of contagion?  Heck yes.  Look at the bottom line:  No mask, 200, homemade mask, 43, proper surgical mask, 30.  That’s the count of bacterial “colony-forming units” that they observed.  Do the math, and a home-made mask gets you (200-43/200-30) = 92% of the reduction that you would get from a standard high-quality surgical mask.

Now in case you’re surprised by that, my reading of it is that anything that stops droplets from flying is good.  You aren’t literally trying to filter out tiny little viruses.  You are trying to filter droplets, most of which you can catch with cloth, some of which fly right through.

Filtering ability of paper towels.  I didn’t find a scholarly article (and got tired of looking), but these people seem to have their act together.  It’s one of those great articles that just gets to the point.  And the short answer is that common household paper towels, do, in fact, have some measurable ability to filter out particles in the size range we are talking about.

For very tiny (0.3 micron) particles, “A single layer of kitchen paper captured just 23% particles. Adding an extra layer only increased particle capture to 33%.”

But for aerosol-sized particles (smaller than “droplets”):  “For larger 2.5 micron particles, paper towel performed better. The single layer of kitchen paper captured 52% of these larger particles”.

(From that, I would infer that two layers would get 75% or so.)

Those same folks provide a nice graphic re-write of the article on home-made masks, at this location.

Near as I can tell, nobody has done the one I want to see, which is a coffee filter.  I use(d) those as a pre-filter when purifying raw water when camping, and I think that’s a pretty common use.   I did test that you could breathe through one (possible, but a lot of resistance).  I will keep looking for that one.


Bottom line:  Wear ’em if you’ve got ’em.  If not, buy one and modify it.  If not, make one from scratch.  Any mask is better than no mask.  Even paper towels have some filtering efficiency. 

Next post is about buying and modifying masks.

Final post will be about making masks.  But you can just go on Amazon and get a free Kindle download on that.