Air Quality Index (AQI) Basics
- The AQI is an index for reporting daily air quality. It tells you how clean or polluted your air is, and what associated health effects might be a concern for you.
- The AQI focuses on health effects you may experience within a few hours or days after breathing polluted air.
- EPA calculates the AQI for five major air pollutants regulated by the Clean Air Act: ground-level ozone, particle pollution (also known as particulate matter), carbon monoxide, sulfur dioxide, and nitrogen dioxide.
- Ground-level ozone and airborne particles are the two pollutants that pose the greatest threat to human health in this country.
How Does the AQI Work?
- Think of the AQI as a yardstick that runs from 0 to 500. The higher the AQI value, the greater the level of air pollution and the greater the health concern.
- For example, an AQI value of 50 represents good air quality with little potential to affect public health, while an AQI value over 300 represents hazardous air quality.
- An AQI value of 100 generally corresponds to the national air quality standard for the pollutant, which is the level EPA has set to protect public health.