It offers great advice on masks that protect us from PM2.5, soot or wildfire smoke. But then it says this:
“No effect” it says. But when I read the cited articles, I saw no tests of surgical masks.
But I should be nerd fair. Maybe they really mean “a small effect.” Then how small would be small? 10% of particles? 20%?
I’ve read three independent tests of surgical masks, and here’s what I learned: surgical masks are shockingly good at protecting against particulate pollution.
Researchers from Edinburgh University tested how much diesel exhaust different masks could block, including a surgical mask. They tested down to .007 microns. That’s way smaller than 2.5 microns. The surgical mask blocked 80% of particles.
In Beijing, Dr. Richard Saint Cyr fit tested several masks on his face using a fancy fit-testing machine.
The surgical mask did a bit worse here – 60%. That’s likely because this is a fit test, and so it takes into account leakage around the mask.
In a study out of the University of Massachusetts, researchers tested N95 masks, cloth masks, and a surgical mask. They tested the masks on a mannequin to mimic effectiveness while a person is wearing it, not just the particle capture rate.
The left-most mask is a 3M N95 mask, the “N95 mask2″ is a Moldex N95, and the right-most mask is a cheap surgical mask bought from a street vendor in Kathmandu. The surgical mask blocked about 60% of .03 micron particles and over 90% of 1 micron and 2.5 micron particles.
Based on scientific fit tests and particle penetration tests, surgical masks as cheap as 1 RMB (US$0.15) block between 60-90% of particles. That includes even the really small particles and even while a person is actually wearing it.
Should You Wear A Surgical Mask?
Now let me be clear. I’m not recommending that everyone use surgical masks. I wear N95 and N99 masks because tests show they fit better and capture more particles. But if professional masks are unaffordable or it’s a bad air day and you forgot your normal mask at home, or even if you’re caught out with a wildfire, ducking into a pharmacy and spending 1RMB on a mask will significantly reduce your exposure to particulate pollution.
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Choon Khin is a Smart Air engineer from Singapore, studying chemical engineering at the National University of Singapore