N95, P100: What do all these mask numbers mean and how do I know it's keeping me safe?

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3M mask for smaller faces.

A particulate respirator like this one from 3M is recommended for filtering wildfire smoke. N95 is recommended for ease of breathing. Higher numbers like N100 or P100 that filter more are also fine, but may be harder to breathe through and more expensive.

With dangerous air quality from the devastating Camp Fire near Chico forcing hundreds of schools to cancel class, hundreds of thousands of parents to scramble for child care, and our lungs to scramble for air, it may be time to actually pay attention to what the numbers and codes on those dust masks really mean.

Anyone who has worked with drywall, removed paint, or crawled into an attic has probably strapped on one of these cheap white masks. N95 is common, and is what's been recommended for smoke, but for a buck or two more, you can get N99. What's the difference? The 95 refers to 95 percent — as in it blocks 95 percent of the particles or "filtration efficiency per the NIOSH CFR 84 Test." And N99? 99 percent And N100? You guessed it. It blocks 100 percent of particulates (well, 99.997% to be exact).

Chart showing types of masks.

N100 is the equivalent of a HEPA filter for your face.

N100 is required for lead and asbestos, but it would certainly be good for smoke. And if you see a "P"? It filters exactly the same stuff – the only difference is, it also filters out oil-based aerosols if you were working with chemicals. A P100 or N100 are both equal in terms of filtering out soot.

CAMP FIRE UPDATES: While the air quality is an on-going health problem impacting millions in California, the actual fire producing the smoke has killed at least 63 people, and 631 missing, in addition to destroying 10,000 homes. Get caught up on the fire fight here.

WHEN WILL THE SMOKE FINALLY CLEAR: New forecast is not good news.

So why do some masks have "snouts" while others don't?

That's to let exhaled air escape. If you’re blowing out, your pressure means particles are not getting in, so the valve lets you exhale quickly, and then it closes and resumes filtering as you suck back in air.

As for the cost, if it's at the 99 Cent store, or Home Depot, does it matter? PK Safety writes in its clear language guide, "It is helpful to note that since government agencies determine these ratings, one N95 mask that is more expensive than another will not provide some kind of "better" N95 protection."

So if you trust the rating system, you may not need to pay more. But the more expensive masks may have better straps and better seals and reinforcement.

Graphic showing how to read markings on a mask.

Some masks are even made for smaller faces, like this one.

If the mask isn't sealed around your face, you’re just breathing through the edges, and it doesn't filter much at all. Men with beards cannot get the full benefit of a mask, and many men have looked at shaving it off for the sake of their lungs.

3M writes in this handy but rather complex guide: "Do not use tight-fitting respirators or loose-fitting facepieces with beards or other facial hair or conditions that prevent direct contact between the face and the edge of the respirator."

Masks for bearded men.

Protective systems recommend a half-face mask or full-face mask if you really want to save your beard, but also filter your air. If you thought people in face masks looked funny when folks first started wearing them, this is a whole other level of awkward, but who knows. Face masks look pretty normal now, so maybe this will too.

The whole point of this article was to provide some clarity. Now, for some confusion:

• Sacramento has stopped recommending masks. They say they make it harder to breathe (since you have to suck air through all those layers of material). Apparently for some people, yes, polluted air is better than no air it they’re short of breath. In a statement from the county, health experts say, "The Sacramento County Public Health Officer does not recommend use of N95 respirator masks for the general public." They add, "The use of the N95 Respirator Mask is only recommended for those near the fire who do not have the option to be indoors or have access to filtered/recirculated air. N95 respirator use by those with heart and respiratory diseases can be dangerous, and should only be done under a doctor's supervision."

• Also, it's unclear how long the masks will protect you. Medical masks are changed often because you don't want germs sitting on the outside that will infect you when you touch them, but particulate masks pretty much work till their pores get "loaded" and filled up. Certainly, a mask doesn't last you all year, but 3M recommends, "Generally these filters should be used and reused subject only to considerations of hygiene, damage, and increased breathing resistance." The California Department of Public Health recommends swapping masks daily, if possible.