HEPA filters for your face
Once again smoke from wildfires is impacting the US east coast, and people are (hopefully) modifying their outdoor activity in accordance. Given the health risks of smoke exposure, if you have to go outside for any length of time in smoky conditions, it really is important to filter the air you breathe. We have long recommended using standalone HEPA filters in your home to filter dust and allergens, especially for those who suffer from respiratory conditions, so the natural question is, is there a HEPA filter equivalent for your face? First, we want to review what HEPA means, and the mask nomenclature mean, to give a good comparison.
According to the EPA, HEPA means “"high efficiency particulate air [filter]". This type of air filter can theoretically remove at least 99.97% of dust, pollen, mold, bacteria, and any airborne particles with a size of 0.3 microns (µm, the same as micrometers). The diameter specification of 0.3 microns corresponds to the worst case; the most penetrating particle size (MPPS). Particles that are larger or smaller are trapped with even higher efficiency. Using the worst case particle size results in the worst case efficiency rating (i.e. 99.97% or better for all particle sizes).
Wildfire smoke contains at least two dangerous components–particle matter and VOCs–so getting the particles out of the air is important. Some particles less than 10 microns in diameter can get deep into your lungs and some may even get into your bloodstream. Of these, particles less than 2.5 microns in diameter, also known as fine particles or PM2.5, pose the greatest risk to health. With a true functioning HEPA filter, you are getting the majority of these small, dangerous particulates out of your breathable air.
“HEPA” is obviously used for standalone purifiers, but what kind of designations are used for facemasks? First of all, facemasks, or respirators, are grouped into at least 3 groups: N, R, and P, based on their reactivity to oil particles. This is because industrial users encounter these oil particles in their lines of work, and oil particles affect filter capability. According to US standards, N means (Not resistant to oil), R (Resistant to oil), and P (oil Proof). For this reason, regular users (non-industrial) will most often encounter the “N” grade. After the letter designation, you will see three levels of filter efficiency are 95%, 99%, and 99.97%. In masks, “99.97” is rounded to 100. The N masks are tested with salt (NaCl), while the R and P masks are tested with an oil (dioctyl phthalate). With this information, you can understand the following table from the CDC:
One more complicating factor is the presence of “KN” masks. KN masks were introduced in China as a counterpart to the N95 respirator and are now made in a number of countries. KN95 and N95 masks are both rated to filter out at least 95% of particles down to 3 microns. The N95 is more effective due to being able to achieve a better fit. They have similar resistance to inhalation and exhalation (which affects breathing comfort), with the N95 being slightly less resistant. (A Mask Q&A: Addressing common questions about the KN95, N95 masks and more)
So, how can we compare “HEPA” with these facemask designations? Since HEPA and N100, R100 and P100 masks filter out 99.97% of particles down to 0.3 microns, the “100” is what you should look for in a facemask, if you want to get the same protection as a HEPA filter. There are not a lot of options for this level of filtration:
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3M Respirator 8233, NIOSH APPROVED, Exhalation Valve, N100: $11 per mask
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4701N100 AirWave® Disposable Particulate Respirator, $14 per mask
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Parcil N100 ProSeal Disposable Respirator Mask NIOSH-Approved, $23-25 per mask
N95 masks are much easier to find, but counterfeits are out there. Here are some ways to spot a counterfeit N95:
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All N95 masks are approved by the U.S. National Institute for Occupational Safety & Health (NIOSH). If there is no “NIOSH” approval, then it is not a real N95. (KN95’s are never approved by NIOSH or the CDC).
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All real N95 masks have head straps, not ear loops. If the N95 mask has ear loops, it’s not a real N95.
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All real N95 masks must be marked in a certain way (see diagram below).
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If there is decorative fabric or decorative add-ons such as sequins, it’s not a real N95.
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If the mask claims that it’s approved for use in children, it’s not a real N95 (NIOSH does not approve any masks for children).
So, there are HEPA filters available for portable use (an N100 facemask), but you’ll only know if these are right for you by trying them out. Since they’re a bit more expensive than N95 masks, you’ll want to know how long it lasts. According to one manufacturer (3M), you can use your N100 mask until it becomes dirty, damaged, or difficult to breathe through. It has a shelf life of 5 years from the date of manufacture. They are to be stored in the original packaging, away from contaminated areas, dust, sunlight.
Similar recommendations exist for N95’s, and according to Linsey Marr, a professor of civil and environmental engineering at Virginia Tech, an N95 mask’s material and filtration ability aren’t “going to degrade unless you physically rub it or poke holes in it.” “You’d have to be in really polluted air … for several days before it lost its ability to filter out particles. So, you can really wear them for a long time” (she wears hers for a week). (How long you can wear your N95, according to experts)
Whichever mask you choose, make sure to have a few N95’s or N100’s on hand for each person in your household just in case the wildfire smoke or urban fire comes near you, because we all know how quickly supplies can disappear when emergencies set in!
