Air Quality Index (AQI)

What is the Air Quality Index (AQI)?

There are several different indices used to report air pollution, BREATHE|Smart monitors report the version issued by the United States Environmental Protection Agency. 

The AQI is an easy way to see 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.

The AQI is a scale that runs from 0 to 500, split into 6 categories of health concern each with an associated colour so it is easy to understand. 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.

Each category corresponds to a different level of health concern:

• Good.

The AQI value is between 0 and 50. Air quality is satisfactory and poses little or no health risk.

• Moderate.

The AQI is between 51 and 100. Air quality is acceptable; however, pollution in this range may pose a moderate health concern for a very small number of individuals. People who are unusually sensitive to ozone or particle pollution may experience respiratory symptoms.

• Unhealthy for Sensitive Groups.

When AQI values are between 101 and 150, members of sensitive groups may experience health effects, but the general public is unlikely to be affected. People with heart or lung disease, older adults, and children are considered sensitive and therefore at greater risk.

• Unhealthy.

Everyone may begin to experience health effects when AQI values are between 151 and 200. Members of sensitive groups may experience more serious health effects.

• Very Unhealthy.

AQI values between 201 and 300 trigger a health alert, meaning everyone may experience more serious health effects.

• Hazardous.

AQI values over 300 trigger health warnings of emergency conditions. The entire population is even more likely to be affected by serious health effects.