Understanding Air Quality Index (AQI): Everything You Need to Know

The Air Quality Index (AQI) is a standard used to report daily air quality. It tells you how clean or polluted your air is, and what associated health effects might be a concern for you.

What do the AQI values mean?

The AQI is divided into six categories, each corresponding to a different level of health concern:

0-50 (Good/Green): Air quality is considered satisfactory, and air pollution poses little or no risk.
51-100 (Moderate/Yellow): Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution.
101-150 (Unhealthy for Sensitive Groups/Orange): Members of sensitive groups may experience health effects. The general public is not likely to be affected.
151-200 (Unhealthy/Red): Everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects.
201-300 (Very Unhealthy/Purple): Health alert: everyone may experience more serious health effects.
300+ (Hazardous/Maroon): Health warnings of emergency conditions. The entire population is more likely to be affected.

Major Pollutants

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, including PM2.5 and PM10), carbon monoxide, sulfur dioxide, and nitrogen dioxide.

How to protect yourself?

When the AQI is high, take simple steps to reduce your exposure:
• Check current air quality in your area.
• Limit outdoor exertion, especially if you fall into sensitive groups.
• Use air purifiers indoors.
• Wear N95 masks if you must go outside during high pollution levels.