Published on January 18, 2025 4:00 PM GMT
In general, you're notsupposed to wear a beard with a respirator mask (N95, P100, etc),at least not in a way where you have facial hair underthe seal:
But how much worse is the fit? A P100 with a beard is going to filterless well than a P100 without a beard, but does it do as well as anN95? Or is it hopelessly compromised? And is stubble as bad as afull beard? Does length matter? In an emergency where I really needmy mask for protection should I shave?
Bottom line up front: with my rough DIY test setup I got 80%filtration with a long beard, 92% with a short one, and 99.7% withstubble. But see my note at the end about a weird effect I saw.
What was my test setup? The goal is to measure the difference betweenfiltered and unfiltered air. I have a TemtopM2000 meter, which I'd bought to measure air quality for testingmy ceiling fanair purifier idea, so I can use that as a sensor. Burning matchesis still a fine way of putting enough smoke in the air that I can seedifferences. And then I can measure the effect of the mask bymeasuring at my 3M HF-802SDelastomeric respirator's exhale valve, with the meter in a bag, andseeing how smoky it is (pm2.5). With the filter cartridges inserted I canmeasure the effect of the mask, while with them removed I'm measuringessentially no filtration. The ratio of particles with vs without thefilters is my filtration efficacy.
This isn't perfect:
My lungs or the the non-filter parts of the mask might be doingsome filtration.
My seal with the bag might not be 100%.
The bag needs to be unsealed to let air out, or it willburst. But maybe this also lets a little smoky air in.
All of these are off in the same direction, however: my measurement islikely to be a lower bound in filtration efficacy.
To actually build this I made a small hole in a gallon ziplock, andattached it around the vent of my elastomeric respirator. The firsttime I did this I used packing tape, which didn't work very well andkept coming loose:
I did it again with duct tape:
I made sure to get a good seal all the way around:
>Then I realized I wanted to test this with a pretty long beard tostart, so put this on hold for a month while growing out my beard. Igot to maybe 1 1/4":
Here's it combed to show the full length, though for all these tests Ihad it flat against my face.
I put on the mask, put the meter in the bag, and the bag started toinflate:
The mask has a fit test button, which blocks the inhalation valve: ifyou can still breathe in with it pressed you know air is making itsway under the seal. I didn't feel much air coming in, but I did feelsome.
I took a series of measurements, alternating filter status.Qualitatively, each time I put the filters in/out it immediatelychanged whether I could smell smoke.
| Filters? | pm2.5 | pm10 |
|---|---|---|
| No | 328.5 | 509.9 |
| Yes | 51.5 | 76.5 |
| No | 264.0 | 400.3 |
| Yes | 49.7 | 74.4 |
| No | 199.2 | 302.5 |
Since I expected the level of smoke in the room to slowly drop overtime, doing interleaved measurements was quite important.
With a full beard, it looks like the mask cut pm2.5 from 263.9 to 50.6(-79%), and pm10 from 404.2 to 75.5 (-81%).
Then I trimmed my beard with a bead trimmer set to 3/8":
This is where I normally trim by beard to:
I tried combing it out, but at this length it doesn't do anything:
I made more smoke and repeated the measurements:
| Filters? | pm2.5 | pm10 |
|---|---|---|
| No | 349.1 | 555.3 |
| Yes | 22.9 | 34.6 |
| No | 338.6 | 539.3 |
| Yes | 25.1 | 37.9 |
| No | 264.4 | 418.5 |
This time the filters brought pm2.5 from 317.4 to 24.0 (-92%) and pm10from 504.4 to 36.3 (-93%).
Then I used the shaver with no guard to remove as much of my beard asI could, getting down to maybe 1/32" stubble:
And from the front:
More measurements:
| Filters? | pm2.5 | pm10 |
|---|---|---|
| No | 436.2 | 713.2 |
| Yes | 1.0 | 1.4 |
| No | 307.0 | 486.6 |
| Yes | 0.8 | 1.0 |
| No | 261.1 | 417.4 |
The filters now took pm2.5 from 334.8 to 0.9 (-99.7%), and pm10 from539.1 to 1.2 (-99.8%). This is great!
Additionally, when I tried the fit test button I now couldn't breathein at all, which actually felt a bit terrifying.
Overall I'm pretty happy with these results, except for one wrinkle:the meter reliably read a higher number when measuring my exhalantthan it did in the ambient air. How could that be?
I tried a few more tests:
Putting the meter in the bag and not blowing in: same asambient, then slowly decreasing (probably particles settling?). Itnever plateaued, just kept going down slowly.
Breathing directly into the bag with no mask: elevated from ambient
Using an air mattress pump to inflate the bag: elevated from ambient
Repeating my test in a room with minimal smoke: probably sameresults but harder to tell because the numbers were small.
Here are the numbers from what I think is the clearest test, using thepump to inflate the bag:
| Status | pm2.5 | pm10 |
|---|---|---|
| Ambient | 156.4 | 235.1 |
| In bag, after waiting and just before pump | 37.0 | 54.9 |
| With pump, after plateauing | 219.6 | 327.5 |
| Ambient | 117.5 | 177.7 |
I don't know where this is coming from, but possibly it's due topressure? I suspect that whatever the effect is it's a scalar effect,and so is compatible with interpreting filtration ratios, but I don'tknow for sure.
This was also the first time my kids had seen me without a beard:
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