Post #627: Another short cost-effectiveness calc. Is anybody listening?

Posted on April 12, 2020

I upgraded my first cloth masks today, inserting Filterete (r) 2500 fabric into commercially-made fabric masks that my wife and daughter are using.  Then whip-stitching them shut.

What I found is that, even if I doubled it up, and provided generous seam allowances, and bought the Filtrete (r) at full retail, it works out to about $0.50 per mask.

Stay with me on this.

Filtrete (r) is a 3M product, and is designed to filter out the most difficult-to-filter particles — those around 0.3 microns.  And it’s designed to do that without causing a large back-pressure.  (Because otherwise you’d screw up your HVAC system, right?)

Those particles are exactly what you want to be able to filter out, these days. Virus-sized, for want of a better term. Aerosols.  Under 5 microns. Ah, I gathered the info a week ago.  (see Post #593 for details)

Those N95 masks that are in such great shortage?  That stands for being able to trap 95% of those small particles, in a single pass, through that mask (really, respirator). That’s the gold standard.

If you look at the specs, via the 3M website (see Post #593 for details), or look at this .pdf on the 3M website, a single layer of 3M Filtrete 2500 removes 77% of E1 particles (down to 0.3 micron) in a single pass.  Two layers?  Simple math. They allow 0.33 * 0.33 = 10% Edit: oops, .23*.23 = 5% of those particles to pass.  So, the same as the N95 standard.

Yeah, there’s caveats.  That’s based on some specific rate of air flow.  And while I may be wrong, I get the feeling that my HVAC unit, with its 1 HP motor running a blower and driving air though 400 square inch filter, probably passes more air per square inch than a wheezy old fat guy, with a mask.  Meaning, me.

Anyway, in mask parlance, two layers of Filterete (r) 2500 creates an N905 mask.  If you can keep air from leaking around the edges of the mask.

And that ain’t too shabby.  For a fifty-cents-per-mask investment.

My point being, there could be a cheap way to end this.  Mask up.  Mask up in public.  Mask up in private business spaces — places where you’re indoors with people other than your family.

And, maybe, way outside the box here, if we all masked up, and followed other CDC guidelines, and had high-quality masks — maybe we could just cut this whole quarantine thing short.

The US powers-that-be won’t consider that, because there aren’t nearly enough N95 or KN95 masks to allow 330M Americans to mask up.  Those are the only Officially-Certified masks.  And KN95, only because FDA was dragged kicking and screaming into allowing that.  Search FDA here, if you want to see the story.

So, screw that.  Let’s make some.  We’re Americans, for gosh sakes.  If we were dumb enough to take an insane king’s word as law, we’d still be part of the British Commonwealth.  But our founders had better sense than that.

Some people are sufficiently behind the times that they think of those N95’s as one-use disposables, instead of nearly-indefinitely re-usable.  So let’s assume that, by now, they’ve all gotten the word that the first thing to wear out on a 3M N95 is the elastic.  And that you can sanitize them against COVID-19 by just letting them sit in an open paper bag.

But the cheap-ass economist in me keeps saying, $0.50 a head, $0.50 a head.   Call it $1.00 per person, if you are fussy enough to require a two-day mask rotation.  For the key material.  Volunteer labor.  Plus fabrics based on whatever scraps you have around.  And half-a-buck’s worth of Filtrete (r) or 13-or-higher MERV per mask.

Seriously, folks.  Fearless Leader is still talking about just letting people die as the expedient path here.  I think the last euphemism was “wash over”.  Just let it “wash over” the populace.  That’s still just the current twist on the old “high cost of dying” canard.  See posts 570 and 571.

I don’t know about you, but if push comes to shove, laws requiring an NXX mask or better, in any place where people interact, just beat the living hell out of the alternatives that are (apparently) being considered by the US executive branch of government.

What we really need is some decent observational data. A handful of communities who will lead the way.  Even the weakest evidence of efficacy makes a mask-up policy  — with good quality home-made masks — vastly better than sitting around, hoping this is going to die down on its own.

Fifty cents a mask.  N905.  Just think about it.

At present, I have enough material, from a single large Filtrete (r) filter, to supply material for an estimated 48 masks.  And I have more on the way.  And non-Filtrete MERV-13’s.  If you live in the Town of Vienna (ZIP 22180) and you’d like a piece of this material, email