Air Quality Data Methodology
How EnvioGrid collects, processes, and presents real-time air quality data including AQI, PM2.5, PM10, NO₂, and O₃ for every ZIP code.
Last updated: May 2025
Data Sources
Air quality data is sourced from two primary APIs:
- Open-Meteo Air Quality API: Provides real-time and forecast air quality data including AQI, PM2.5, PM10, NO₂, and O₃. Data is sourced from the nearest monitoring station to each ZIP code's geographic centroid.
- OpenAQ: Supplemental air quality data from official government monitoring stations worldwide.
AQI Calculation
The Air Quality Index (AQI) is calculated using the EPA's standard methodology:
- PM2.5: 0-12 µg/m³ (Good), 12.1-35.4 µg/m³ (Moderate), 35.5-55.4 µg/m³ (Unhealthy for Sensitive Groups)
- PM10: 0-54 µg/m³ (Good), 55-154 µg/m³ (Moderate), 155-254 µg/m³ (Unhealthy for Sensitive Groups)
- The overall AQI is the maximum of all pollutant sub-indices
Data Freshness
Air quality data is refreshed every hour. If a monitoring station is unreachable, we preserve the most recent historical data and mark the record as "not reachable."
Limitations
- Data represents conditions at the nearest monitoring station, which may not reflect hyperlocal conditions
- Not all ZIP codes have a monitoring station within 50km — in these cases, data may be interpolated from nearby stations
- AQI values are rounded to the nearest whole number