Air Quality Checker

Particulate matter under 2.5 microns — combustion products from wildfires, vehicles, and industry, small enough to reach deep lung tissue and cross into the bloodstream, which is why it carries the strongest health evidence of any common pollutant (cardiovascular and respiratory effects, not just irritation). During smoke events PM2.5 is essentially the whole story. The AQI reports whichever pollutant is worst at the moment; on most bad days in most places, that's PM2.5, with summer-afternoon ozone the other regular.

The EPA bands, translated to decisions: under 50, no adjustments for anyone. 51–100, only unusually sensitive individuals notice. 101–150, the sensitive groups threshold — asthma, heart conditions, kids, elderly, and pregnant people should trim prolonged outdoor exertion (this is when youth sports should move practice indoors). 151–200, everyone cuts strenuous outdoor activity; exercise indoors. 200+, stay in with windows closed and filtration running. The multiplier to remember: exertion multiplies dose — a run at AQI 130 inhales far more pollution than a walk at 160.

Indoors: close windows, run HVAC on recirculate, and use HEPA filtration — a real purifier, or the legitimately effective DIY version (box fan + MERV-13 furnace filter). Outdoors when unavoidable: N95/KN95 respirators genuinely filter smoke particles; cloth and surgical masks essentially don't (smoke particles are far smaller than droplets). Skip outdoor exercise entirely at unhealthy levels. And a car isn't a bubble — set its ventilation to recirculate too. Smoke events end; the goal is minimizing the cumulative dose while they last.

Different sources measuring different things: this uses a model (Open-Meteo, blending satellite and ground data) that's smooth and gap-free but can lag fast-moving local smoke; PurpleAir shows raw hyper-local sensors that respond instantly but run hot without correction factors; official EPA monitors are accurate but sparse and hours-delayed. Disagreement is normal during dynamic events. The honest hierarchy: for 'should I run today,' any of them suffices; during active smoke, trust the most local signal available — including your own eyes and nose, which outrank a lagging model.