(Last Updated On: March 24, 2023)

What Is the Air Quality Index?


The Environmental Defense Fund estimates that around 40 percent of Americans live in a place with unhealthy levels of pollution. The EDF says the main contributor is smog – which is caused by emissions from cars, factories, power plants and various other sources. But there are plenty of other impurities floating around in the air we breathe. It can cause problems for those without any health issues, but can be especially difficult for those who have allergies, asthma or more serious ailments like COPD or lung cancer.

Some days the air is better than others, and that’s why the Environmental Protection Agency (EPA) decided it was important to put a system in place that measures air quality.

air quality index meter

What is the Air Quality Index?

In 1976, the EPA designed a national index for air quality. The Air Quality Index (AQI) is a daily report that’s easy to understand and helps Americans know if spending more time indoors on any particular day is a better option for your respiratory system.

The AQI is broken down into color-coded categories. Each category represents a different level of concern and comes with an explanation about the air quality for a particular area. The AQI also indicates who may be affected and ways you can cut down on your exposure to air pollutants.

What pollutants does the AQI cover?

The AQI covers five major pollutants:

  • Ozone
    • Ozone is a gas created by chemical reactions. It occurs when pollutants from cars, refineries, chemical and power plants, industrial boilers and a variety of other sources chemically react with sunlight.
  • Particle pollution
    • Particle pollution is always present in the air we breathe – both outside and inside. It’s a mixture of things like dust, dirt, pollen or even acids and inorganic compounds that become suspended in the air.
  • Carbon monoxide
    • Carbon monoxide is a colorless, odorless gas. It comes from cars, trucks and machinery that burn fossil fuels. Gas appliances and leaking chimneys or furnaces can also create carbon monoxide.
  • Nitrogen dioxide
    • Nitrogen dioxide is a gas that forms when things like coal, gas, wood, natural gas or diesel are burned at high temperatures.
  • Sulfur dioxide
    • Sulfur dioxide is a gas that forms when things like coal, oil or diesel are burned. Coal-fired power plants, electricity generation, industrial boilers, petroleum refining and metal processing are large sources of sulfur dioxide.

All five pollutants fall under the Clean Air Act which regulates air emissions to protect public health. The daily AQI for each of them is based on air quality and scientific information standards.

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What are the Air Quality Index categories?

There are six color-coded categories for the Air Quality Index. Each category has a numerical value and the lower the number the better the air you’re breathing.

  • Green is the lowest level of concern for air quality. It means the air quality is good and there is little to no risk for air pollution.
  • The color yellow indicates a moderate risk. The EPA considers the air quality to be acceptable in the yellow range but it may pose a risk for those who are highly sensitivity to air pollution.
  • If the air quality is coded orange that means it is unhealthy for anyone who has respiratory issues.
  • Red indicates the air quality is unhealthy for everyone. The general public may have breathing issues, and those with underlying conditions can experience serious side effects.
  • Purple means the air quality is very unhealthy and everyone’s risk of health problems increases.
  • Maroon is the highest alert level. It means the air quality is hazardous and a health warning is issued for everyone.


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How can I know what the AQI is for my location?

It’s a good idea to be aware of the Air Quality Index on a regular basis. For anyone with respiratory issues that range from allergies to lung cancer, it’s even more important to know the quality of the air outside.

There are several ways to find out what the AQI is for any given day. The EPA requires cities with a population of more than 350,000 to report the Air Quality Index daily. Many smaller cities will report the AQI as a public service.

You can check it daily by going to https://www.airnow.gov/ and typing in your zip code. There’s also an app you can download called EPA AIRNow, so you can see what the air quality is right from your smartphone or tablet.

Tuning in to your local newscast is another way to find out the Air Quality Index. It is often reported during the local weather segments.


How can the air quality impact my health?

Air is obviously vital to our lives. We need it to survive. But dirty, pollution-filled air can be bad for us immediately and over the long-term. When the air quality is bad, it can be difficult to breathe – even for the healthiest among us. It can immediately cause irritation to your eyes, nose and throat. Prolonged exposure can cause serious lung problems and heart disease.

Studies have shown that air pollution can affect lung development and lead to emphysema, asthma and even COPD. Particle pollution and nitrogen oxide are factors in chronic bronchitis. Particle pollution can also cause your arteries to calcify quicker and impair the way your blood vessels function. And all five of the air pollutants the Air Quality Index measures have been shown to increase the risk for breast and lung cancer, as well as lymphoma.

Children, pregnant women, the elderly, and anyone with pre-existing heart and lung conditions can be especially vulnerable to air pollution. And you can be extremely healthy, but live near an industrial source of air pollution that can end up causing you long-term issues.

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What can I do when the Air Quality Index is unhealthy?

The air quality can still affect you – even if you’re healthy. So, one of the first things you can do to protect yourself and your family is to be aware. Monitoring AQI is the first step towards improving your personal air quality, however once that is under control you will want to look into the number of smaller particles in your environment. Check the Air Quality Index regularly, especially on days when the weather is warmer. Heat and sunlight react with the pollutants the AQI measures and can cause poor air quality.

If the level for any given day is orange, red, purple or maroon – stay inside as much as possible. Those colors indicate pollution in the air is high, unhealthy and can cause serious issues for you. Avoid exercise and other vigorous activities outside. If you have respiratory diseases, poor air quality can cause coughing, wheezing, shortness of breath, chest discomfort and fatigue. If you have heart disease, poor air quality can cause shortness of breath, fatigue, chest pain or tightness and heart palpitations.

We may not be able to control the air quality outside, but to improve the air quality in your home on a consistent basis, consider investing in an air purifier. One equipped with a HEPA filter is your best choice. HEPA stands for high efficiency particulate air and the filter will pull more than 99 percent of contaminants out of the air and push clean air back out. It will help everyone in your home breathe easier, especially those who have respiratory issues.

Air Purifier ExpertAbout the Author: Mark Vander Berg

Mark Vander Berg is the Chief Product Expert at AirPurifiers.com. Mark has decades of experience in air purifier engineering. In addition to engineering and product design, he has also done extensive research and testing of many air purifiers and continues to do so for AirPurifiers.com.