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Which mask works against smog? A buying guide
Last reviewed 4 Nov 2026 · DanixSoft
For smog you need a respirator that filters fine particles and seals to your face: an N95 (US standard), KN95 (China) or FFP2/FFP3 (EU). Each filters at least about 94–95% of fine test particles (FFP3: 99%) when it fits. Cloth and loose surgical masks do little against PM2.5. Fit matters as much as the label: air leaking around the edges skips the filter.
The standards
| Type | Standard | Filtration (lab test) | Notes |
|---|---|---|---|
| N95 | US NIOSH (42 CFR Part 84) | ≥ 95% | Head straps; approval number "TC-84A-…" printed on it, checkable online. |
| KN95 | China GB 2626-2019 | ≥ 95% | Usually ear loops; many fakes, buy from a known seller. |
| FFP2 | EU EN 149 | ≥ 94% | Look for "EN 149" and a CE mark with a four-digit number. |
| FFP3 | EU EN 149 | ≥ 99% | Harder to breathe through; for very bad days. |
| Surgical / cloth | none for smog | low for PM2.5 | Gaps at the sides; fine for germs from the wearer, not for smog. |
Getting a good fit
- Pinch the metal nose strip to the shape of your nose.
- Breathe in sharply: the mask should pull in slightly. Breathe out: no air should rush past your eyes or cheeks.
- Beards and stubble stop a seal forming.
- Head straps seal better than ear loops; an ear-loop "hook" behind the head helps.
Spotting fakes
- N95: check the approval number on the NIOSH Certified Equipment List.
- Be wary of a "N95" with ear loops, no approval number, or claims like "99.9% virus protection".
- Buy from pharmacies and sellers with a return policy; very cheap multi-packs are a warning sign.
Children, valves and reuse
- N95s are made for adults. For children choose a child-size KN95 or similar that seals; never put a mask on a child under two.
- Exhalation valves make breathing out easier and do not reduce your protection from smog.
- Replace a mask when it is dirty, damaged, wet, or harder to breathe through. Rotating a few masks and letting them dry helps them last a few days of commuting.