AIR QUALITY INDEX (AQI): EXPLAINED

01/06/2021 10:01

Air Quality Index or AQI is an indicator to understand the quality of air. It shows the pollution status in the air with a numeric scale ranges from 0 to 500 as well as with different color indicators. The index represents how clean or polluted the air is in a specific area. Polluted air can bring about health concerns; hence, it is necessary to keep watch on AQI to reduce the exposure in air pollution. Five pollutants are usually taken into consideration to generate the air quality index. They include particulate matters (PM), ground-level ozone (O3), carbon monoxide (CO), sulfur dioxide (SO2), and nitrogen dioxide (NO2).

How AQI works

AQI runs on a scale of 0 to 500 and also indicated by colors. Lower AQI value represents the clean air, and a higher AQI value represents the polluted air. An AQI below 50 is considered a good quality of air, and it becomes unhealthy when it crosses 100. If the AQI is more than 200, then the pollution level is very high. An AQI of 300 and up indicates dangerous air quality.

EPA works to establish national air quality standards as a way of controlling air pollution. The table below shows the AQI category, index values, and the breakpoints for different pollutants for a while.

AQI Category Index Values PM2.5 (24-hour) CO (8-hour) NO2 (1-hour) O3 (8-hour) SO2 (1-hour)
Good 0 - 50 0.0 - 12.0 0.0 - 4.4 0.0 - 53.0 0.0 - 0.054 0.0 - 35.0
Moderate 51 - 100 12.1 - 35.4 4.5 - 9.4 54.0 - 100.0 0.055 - 0.07 36.0 - 75.0
Unhealthy for sensitive groups 101 – 150 35.5 - 55.4 9.5 - 12.4 101.0 - 360.0 0.071 - 0.085 76.0 - 185.0
Unhealthy 151 – 200 55.5 - 150.4 12.5 - 15.4 361.0 - 649.0 0.086 - 0.105 186.0 - 304.0
Very Unhealthy 201 – 300 150.5 - 250.4 15.5 - 30.4 650.0 - 1249 0.106 - 0.2 305.0 - 604.0 (24hr)
Hazardous 301 – 400 250.5 - 350.4 30.5 - 40.4 1250.0 - 1649.0 0.405 - 0.504 (1hr) 605.0 - 804.0 (24hr)
Hazardous 401 – 500 350.5 - 500 40.5 - 49.4 1650.0 - 2049.0 0.505 - 0.604 (1hr) 805.0 - 1004(24hr)

Data source: EPA AQI Breakpoints
Read our reviews on Best Air Quality Monitors

Understanding the AQI

The main aim of AQI is to help you master the air quality in your local area. You will get to know the AQI levels from the colors which are used to depict them. Here are some of the colors and the air pollutions levels indicated:

Good: The green color indicates it. The AQI levels are below 50. It is a state which indicates good air quality. There is low pollution and there at risk at this stage.

Moderate: The level is indicated by yellow color and ranges from 51 – 100. In this condition, there is tolerant pollution. There is no high risk to the environment at this stage.

Unhealthy for sensitive groupsSome people are vulnerable to air quality. They will start developing complications when the air quality reaches between 101 and 150. It is indicated by orange on the AQI levels.

Unhealthy: It is a condition where the experts consider the air quality is unhealthy. It ranges from 151 to 200 AQI. The color red indicates the air condition is at harmful levels. Something should be taken to purify the air before your family members can breathe it.

Very unhealthy: At this stage, the AQI level swill indicates purple. It ranges from 201 to 300 AQI. The condition can pose several risks to human beings. Experts warn of several pollutants in the air.

Hazardous: In this stage, the AQI will range between 301 and 500. It indicates by maroon color. At this stage, there are a lot of particles in the air that pose a danger to human life.

The different colors used to explain AQI should be taken into consideration in your air quality monitoring. The experts are careful to offer the information so that you can reduce the health risk from breathing polluted air.

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