When Should You Wear a Mask for Air Quality?

Cloth masks and surgical masks are designed for droplets, not smoke. For air pollution, well-fitted N95, KN95, or FFP2 respirators filter fine PM2.5 when worn correctly. The question is when that extra protection is worth the discomfort.

AQI levels that justify a respirator

At green and moderate AQI, healthy adults usually do not need masks for brief outdoor errands. Orange (101–150): consider a respirator if you are in a sensitive group and cannot shorten time outside. Red and above, or any wildfire smoke event: N95/KN95 protection is recommended for outdoor work, queuing, or commuting when you cannot avoid exposure.

Construction workers, cyclists beside traffic, and people with lung disease benefit earlier than the general public. Children under about seven often struggle with fit — reducing outdoor time beats a loose mask.

• Wildfire smoke: wear N95/KN95 outdoors regardless of visible haze.
• AQI 150+: respirator for anyone outside more than a few minutes.
• Sensitive groups: consider masks from AQI 101 if exertion is unavoidable.
• Indoors: masks are a poor substitute for sealing windows and filtering air.

Fit and limits

A gap at the nose bridge lets polluted air bypass the filter. Press the metal strip, avoid beards that break the seal, and replace masks when breathing resistance increases or after heavy smoke use.

Masks do not filter ozone or carbon monoxide — they target particles. On high-ozone summer days, timing outings for morning still beats masking at noon.