What does the AQI number actually measure?
It's a composite score built from the pollutant with the worst reading at that moment — usually fine particulate matter (PM2.5) or ground-level ozone. The EPA reports whichever pollutant scores highest rather than averaging them together, since one bad pollutant can matter more than several mild ones.
What's a "good" AQI reading?
Anything from 0–50. At that level, most people can go about outdoor activities as usual. Readings above 100 start to affect sensitive groups — kids, older adults, and anyone with asthma or a respiratory or heart condition.
How do I check the AQI for my ZIP code or state?
Government tools like AirNow pull live readings from monitoring stations and satellites and let you search by ZIP code or city. Filterbuy's live AQI maps below cover every state, plus dozens of major metro areas, for a quick real-time check.
Does outdoor AQI affect the air inside my house?
Yes — not always in exact proportion, but outdoor pollution works its way indoors through doors, windows, and your HVAC system. Indoor air can also carry its own pollutant sources, which is why closing up the house and running a high-quality filter both matter on a bad-air day.
What's the difference between AQI and a pollen or allergy forecast?
AQI tracks pollution — particles, ozone, and other airborne chemicals. Pollen counts are tracked separately by allergy forecasts. Both can spike at the same time (wildfire smoke season often overlaps with fall allergy season), which is why it's worth checking both.
What can I do at home when the AQI is high?
Close windows and doors, run your HVAC system on circulate, and use the highest-MERV filter your system can handle. A portable air cleaner can help in bedrooms or common areas if outdoor air stays unhealthy for several days.
