How do you know if your face mask is really working?
Dr. John Volckens is a professor of mechanical engineering at Colorado State University who has been studying face masks and says people should look to the "assigned protection factor" or APF, which is used to measure respirators.
"Let’s say you have a mask with a protection factor of 10. So that means if there were 100 COVID particles floating around outside of your mouth, when you inhale that air, a factor of 10 protection means that if there were 100 particles, only 10 would get through. So 90 of those particles would be filtered out by the mask."
The higher the number, the better. An N95, which filters out 95% of particles, has a protection filter of 20.
The American Society for Testing and Materials has also established its own standard, and masks that meet it will bear an "ASTM" symbol.
Of course, many homemade and cloth masks are not going to be subject to rigorous testing of this sort. Dr. Volckens said that these masks will not be as effective as an N95, but there are a few things to look out for to know if your mask is really working.
"No mask is effective if it doesn’t fit snugly on your face. And by ‘fits’, we mean comfort, but what we really mean is does that mask provide a seal across your face."
Double masking will also boost your protection.
Dr. Volckens told KCBS Radio's "Ask An Expert" on Thursday that while some people may become disheartened when they hear about mask wearers contracting COVID-19, the important thing to remember is that while nothing is 100% effective, wearing a mask can greatly reduce your risk.
"You can drive a car with the best safety equipment possible and wear your seatbelt and drive at the speed limit and you can still get seriously injured in a car crash, right? There’s no perfect ‘safe’. And so no form of personal protection will give you 100 percent protection, a guarantee that you will not get infected. But a protection factor of 10 is great."
