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Air Quality Index

The Air Quality Index (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. You can check the daily air quality forecast on this website or by downloading the Clean Air Make More mobile application for your smartphone or tablet.

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. For each of these pollutants, EPA has established national air quality standards to protect public health.

Understanding the AQI

The purpose of the AQI is to help you understand what local air quality means to your health. To make it easier to understand, the AQI is divided into six categories:

How Does the AQI Work?

The AQI is similar to a yardstick that runs from 0 to 500. The higher the value on the AQI, the higher the amount of pollution in the air. Higher AQI values also mean greater concern for people’s health. For example, an AQI value of 50 in the “green” range represents good air quality with little potential to affect public health. Likewise, an AQI value over 300 in the “maroon” range represents hazardous air quality.

Each category corresponds to a different level of health concern. The six levels of health concern and what they mean are:

Air Quality Index (AQI) Values Levels of Health Concern Colors
When the AQI is in this range …air quality conditions are: …as symbolized by this color:
0 to 50 Good Green
51 to 100 Moderate Yellow
101 to 150 Unhealthy for Sensitive Groups Orange
151 to 200 Unhealthy Red
201 to 300 Very Unhealthy Purple
301 to 500 Hazardous Maroon

“Good” The AQI value for your community is between 0 and 50. Air quality is considered satisfactory, and air pollution poses little or no risk.

“Moderate” The AQI for your community is between 51 and 100. Air quality is acceptable; however, for some pollutants there may be a moderate health concern for a very small number of people. For example, people who are unusually sensitive to ozone may experience respiratory symptoms.

“Unhealthy for Sensitive Groups” When AQI values are between 101 and 150, members of sensitive groups may experience health effects. This means they are likely to be affected at lower levels than the general public. For example, people with lung disease are at greater risk from exposure to ozone, while people with either lung disease or heart disease are at greater risk from exposure to particle pollution. The general public is not likely to be affected when the AQI is in this range.

“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 more likely to be affected.

Source: www.airnow.gov