Post #644: First mask liner for distribution

Posted on April 14, 2020

This is the first model of “mask liner” that I am offering to anyone in the Town of Vienna who would like them. I will go learn Google Forms tonight and set up a form for requesting these, tomorrow.

The base of the mask liner is cheap commercially-made “single-use” mask, not suitable for use by hospital workers.  That’s the blue mask pictured above.  I then pleat a piece of Filtrete (plus thin cover cloth) and staple that over the outside of the mask.  Finally, I add a stiff full-length metal nosepiece in the form of a galvanized wire.

Here, so as not to waste the Filtrete, I used a piece of printed cloth.  The actual masks will be plain white on the outside.

My intention with making mask liners is that you would wear this under your regular cloth mask.  The small size and weak elastic makes these potentially quite “leaky”, and this really should be used with a tight-fitting cloth mask pressing this against your face.

In an emergency, you could wear this as a mask, by itself, but that’s inadvisable due to the potential for air leaks.  If you were forced to do that, you would be well advised to add a couple of pieces of string to the loops on the nosepiece, then tie those behind your head and pull this more tightly against your face.

Surgical-style masks like these are compromised by air leaks, so the nosepiece is important.  If your existing mask has a good metal nosepiece and fits snugly against the bride of your nose and cheeks, order the version of the mask liner that does not have a nosepiece.  The additional nosepiece will just be in the way.  And wear this so that this mask liner is held snugly to your face by your existing mask nosepiece.  If you have a mask that lacks a good nosepiece, then order the version of the liner that includes a nosepiece, as pictured above.

I make no warranties as to how well these work.  I make no warranties that they work at all.  You use these completely at your own risk.

The theory behind this is that it should help filter out smaller particles, of a size that cloth mask is probably unable to filter well, if at all.  In particular, Filtrete 2500 claims to catch 77% of particles down to 0.3 microns.  Two layers should, in theory capture 95% (but I have not tested that yet for breathability).

Surgical masks do not seal to the face the way respirators do.  No matter what you do with a surgical mask, short of literally taping it to your face, you will breath some unfiltered air.  And the harder it is to breathe through the mask, the more air will go around the mask.  So I have tried to keep this as breathable as possible.

These take longer to make than I had hoped.  So I’m not sure how fast I can make them. At some point, if you have a stapler, it might be more expeditious for me to mail these out as kits, rather than assembled.  All you need is a stapler, four clothespins, and (if you need the nosepiece) a few pieces of high-quality tape.  I would supply the rest.

Do not wash these masks.  Washing reduces the filtration ability of most high-quality filtering material.  You should treat these masks exactly as hospital workers now treat N95 respirators for re-use.  Wash your hands, carefully take it off your face (without touching your face), drop it in an open paper bag, and leave it for a while.   The virus self-destructs over time.  How long is a while?  If you are phobic, leave it for three days.  Otherwise, two days.  So if you plan to be out every day (which I think is bordering on crazy unless your job requires it), you’d want two of these, to use in rotation.

How long will these last?  I suspect that the elastic will break early on, but as long as you are using these under a tight-fitting cloth mask, that’s just a nuisance.  The filter material should be good for hundreds of hours of breathing, but I have to do a calculation to determine just how long it should last (based on the rated lifetime of the original filter assembly, and so on).

My intent here is that this would be used when (e.g.) on a weekly shopping trip.  Or when going to the doctor.  I don’t really see these as suitable for use on an 8-hour shift, day after day.  I don’t think they’ll last that long, owing to the generally cheap construction.

I’ll have the form up tomorrow to allow you to order this, or order a kit of materials to make these, or just order up a piece of Filtrete, if you have a cloth mask with a filter pocket in it.  Likely, I’ll ask you to pick your up off my front porch.  If you’re hesitant to take this as a gift, then donate a few dollars per mask to some worthy Vienna-centric charity.

Whether or not Filtrete will work, as advertised, in this case, is purely an act of faith.  For all the world, the stuff looks like a pleated piece of paper with some fibers on one side.  But you have to trust something.  I trust 3M.

That said, you get no guarantee from me.  It should work, but there is absolutely no way to test that, under the circumstances.

Finally, extra points for any old-timers who recognize the brand of tape measure.  Ya’ can’t hardly get those any more.