Masks for haze: N95, surgical or cloth?

Published 19 October 2026

Haze smoke is mostly PM2.5, particles small enough that only a fitted respirator stops most of them. Here is which mask is worth wearing, and when.

What is in the air you are filtering

Smoke from peat and forest fires is a mix of gases and particles, and the particles are what most of the harm comes from. The ones Kabut reports as PM2.5 are 2.5 micrometres across or smaller, roughly thirty times thinner than a hair. They are small enough to pass through the weave of ordinary fabric and around the edges of a loose mask, and small enough to reach deep into the lungs. What PM2.5 is covers why that matters.

A mask does nothing for the gases in smoke. It can only stop particles, and only the air that actually passes through it.

The kinds of mask

N95, KN95 and KF94. These are respirators, not just masks. The names are standards from the United States, China and South Korea, and each means the material filtered at least 94–95% of test particles in the size range that is hardest to catch. They are shaped to seal against the face, so the air you breathe goes through the filter rather than around it. This is the kind Kabut's advice means when it says "wear an N95". FFP2 masks sold in Europe are an equivalent standard.
Surgical masks. The flat, pleated kind. The material filters reasonably well, but the mask sits loosely, and air takes the easy path through the gaps at the cheeks and nose. Against fine smoke it helps a little; it is not a substitute for a respirator.
Cloth masks and scarves. A wet towel or a cotton mask can make smoke smell less strong, which is not the same as filtering it. The weave is far too open for PM2.5, and the class advice says so plainly: a cloth mask does not stop PM2.5.

Buy from a pharmacy or a seller you trust. Counterfeit respirators exist, and a printed standard on the packet is no guarantee that the mask meets it.

Fit matters as much as the filter

A respirator that leaks at the edges filters only part of what you breathe. Getting the seal right is most of the benefit.

Use both straps, or the ear loops pulled snug. One strap left loose lets the bottom edge lift.
Pinch the nose clip around the bridge of your nose with both hands, not one, so it follows your face rather than folding to a point.
Do a quick check every time. Cover the front with your hands and breathe out sharply. If you feel air on your eyes or cheeks, adjust and try again. Breathing in, a well-fitted respirator pulls in slightly against your face.
Facial hair breaks the seal. Stubble and beards under the edge leave gaps a respirator cannot close. Being clean-shaven where the mask touches is the only fix.
Size matters. Many respirators come in more than one size. If it gaps at the sides however you adjust it, try another model or size.

Some respirators have an exhalation valve on the front. It makes breathing out easier and protects you just as well, but the air you breathe out leaves unfiltered.

When a mask is worth wearing

Kabut's advice follows the class of the reading, and the mask advice starts at Unhealthy (US AQI 151 and above):

Good, Moderate, Sensitive groups. No mask advice. At Sensitive groups the advice is to shorten outdoor exertion, not to mask up.
Unhealthy. Limit time outdoors, avoid hard exercise, and wear an N95 outside.
Very unhealthy. Avoid outdoor activity; wear an N95 if you must go out.
Hazardous. Stay indoors with the windows shut, and wear an N95 for any trip outside, however short.

A mask is the last line, not the first. Staying indoors with the windows shut during the worst hours lowers what you breathe for the whole day; a mask only covers the time you spend outside. Keeping indoor air cleaner is the other half of this.

Each city page shows the current class and an hourly forecast, so you can see whether an errand can wait for a better hour.

Children

Respirators are made for adult faces, and on a small face they rarely seal. A few makers sell children's sizes for older children; check that the fit check above works before relying on one. Children under two should not wear masks at all.

For young children, keeping them indoors in a room with cleaner air does more than any mask. If your child has asthma or another breathing condition, ask a doctor what they recommend for a haze season.

If breathing through one is hard

A respirator makes breathing slightly harder by design. For most people that is only uncomfortable. If you have a heart or lung condition, or you are pregnant, ask a doctor before relying on one for long periods. If you feel dizzy or short of breath while wearing one, take it off once you are somewhere with cleaner air.

How long one lasts

Respirators are made to be disposable. You can wear one for more than one short trip, but replace it when:

it is damp, dirty or damaged;
the straps have stretched and it no longer passes the fit check;
breathing through it has become noticeably harder.

Do not wash one or spray it with disinfectant: water and alcohol damage the filter material.

This is general information, not medical advice.