Wildfire, Smoke & Air Quality
What Is the Air Quality Index (AQI)?
AQI translates pollutant concentrations into a public health category, commonly using PM2.5, ozone, or other regulated pollutants.
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Quick answer / What to check next
Quick answer
The Air Quality Index, or AQI, is a public scale for communicating air pollution levels in a way that is easier to scan than raw pollutant measurements.
What this signal means
AQI helps people notice when air quality may affect outdoor activity, travel visibility, school operations, or the need to review official health recommendations.
What to check on HazardNow
Current AQI category, pollutant driving the AQI, station freshness, and whether PM2.5 is elevated.
Verify with official source
AirNow
Quick read
- Useful for
- Comparing air-quality severity without reading raw pollutant units first.
- Watch
- dominant pollutant, monitor location, averaging period, category, and data freshness.
- Confirm with
- AirNow, local air agencies, and EPA pollutant guidance.
- Remember
- The same AQI number can come from different pollutants with different behavior.
What AQI is compressing
AQI is an index, not a direct measurement. It converts pollutant concentrations over defined averaging periods into categories such as Moderate or Unhealthy.
For smoke events, PM2.5 often drives the AQI. For summer smog, ozone may dominate, so source behavior and timing can differ.
Visual reference
AQI category bands
Higher bands indicate larger pollutant concentration ranges and greater need to read official health guidance.
Official sources to verify
Use these links to verify current source text, update timing, and agency caveats.
Last reviewed: . This page explains general preparedness information and does not replace official instructions.
FAQ
Is AQI the same as PM2.5?
No. PM2.5 is one pollutant measurement. AQI is a category scale that can be driven by PM2.5 or other pollutants.
Why can AQI apps disagree?
They may use different monitors, sensors, interpolation methods, refresh times, or pollutant calculations.
Related terms
Check the live HazardNow dashboard
Use this page to understand Air Quality Index. Use the live dashboard to see current alerts, infrastructure stress, weather, wildfire, travel, public-health, supply-chain, and stability indicators in one place. Focus on pm25, wildfire-smoke, fire-weather in the live view.