Post #790: Cigarette smoke does not work as a test for mask filtration ability

Way back in Post #750, 7/9/2020, I had the notion to use cigarette smoke to test the ability of masks to filter out aerosol-sized particles.  There is a need for some sort of home test, because it’s next-to-impossible to tell how well or poorly any off-the-shelf mask works.  That’s particularly true for the “KN95” masks now being sold in everywhere (Post #747).

The theory seemed sound.  Cigarette smoke particles are about the right size, and in the past, some people did in fact use N95 masks to try to avoid second-hand smoke.

Now, having executed this test on my back porch this afternoon, I can attest that it doesn’t work at all. I can smell cigarette smoke strongly right through a genuine (but quite old) 3M N95 respirator (upper left, above).  And I could not tell that the smell of smoke was any stronger when I used a worn-out 3M N95 dust mask (next), or a dust/surgical mask (blue) with no aerosol filtration capability.

I’m not sure why this was such a clear crash-and-burn.  One possibility is that the best masks do filter out 95% of smoke particles, but that the remaining 5% of the particles in a cigarette slipstream are more than enough to convey the strong odor of smoke.  If so, I’d need to create more “dilute” smoke than I got by literally sticking my face into the cigarette slipstream.  (But if so, I don’t know how to achieve that in any reproducible manner).  A second possibility is that any small leaks will allow the smell of smoke to permeate the mask.  Since you can never get any mask or respirator of this type to seal fully, the test is compromised by the leaks.

I don’t think it really matters.  As far as I can tell, this test does not work at all  to distinguish masks based on their ability to filter aerosols.  If you rely on some generic “KN95” mask from the hardware store (pictured above), you really have no way to tell how well or poorly that mask filters out aerosol-sized particles.