Air Quality Index

Using Air Quality Information to Protect Yourself from Outdoor Air Pollution

What Is the Air Quality Index?

Ever hear your local weather forecast say that tomorrow will be a "code orange" day for air pollution? That's the Air Quality Index at work. The Air Quality Index, or AQI, is the system used to warn the public when air pollution is dangerous. The AQI tracks ozone (smog) and particle pollution (tiny particles from smoke, power plants and factories, vehicle exhaust, and other sources), as well as four other widespread air pollutants. Newspapers, radio, television, and websites report AQI levels year-round. Keeping track of the current air quality information in your area can help you take steps to protect yourself, children, and others from unhealthy levels of air pollution.

Name Index Value Advisory
  Good 0 to 50 None
  Moderate 51 to 100 Usually sensitive individuals should consider limiting prolonged outdoor exertion.
  Unhealthy for Sensitive Groups 101 to 150 Children, active adults, and people with respiratory disease, such as asthma, should limit prolonged outdoor exertion.
  Unhealthy 151 to 200 Children, active adults, and people with respiratory disease, such as asthma, should avoid outdoor exertion; everyone else should limit prolonged outdoor exertion.
  Very Unhealthy 201 to 300 Children, active adults, and people with respiratory disease, such as asthma, should avoid outdoor exertion; everyone else should limit outdoor exertion.
  Hazardous 301 to 500 Everyone should avoid all physical activity outdoors.

Why Should I Pay Attention to the Air Quality Index?

Air pollution can harm anyone, but it can be especially dangerous for many people, including children and teens, people with asthma and other lung diseases, anyone over 65, people who have diabetes or cardiovascular disease or who are pregnant. Even healthy adults who exercise or work outdoors can be harmed. Being aware of when the air quality is bad gives you the chance to take steps to protect your health.

How Does the Air Quality Index Work?

Air pollution levels are measured daily and ranked on a scale of 0 for perfect air all the way up to 500 for air pollution levels that pose an immediate danger to the public. The AQI breaks air pollution levels into six categories, each of which has a name, an associated color, and advice to go along with it. AQI values at or below 100 are considered satisfactory for almost everyone. When AQI values are above 100, air quality is unhealthy. The higher the number, the more people are at risk of health harm. 

What Can You Do to Protect Yourself and Your Family?

  • Don't assume that you're safe just because you're healthy. Air pollution can threaten anyone's health. Be aware of how you feel on high pollution days and take steps to help protect yourself.
  • Are you or someone in your family at higher risk from air pollution? Children and younger adults, people who are pregnant or living with a chronic illness are all at higher risk. So are people who spend a lot of time outdoors. They are the first to feel the effects of ozone and particle pollution, and they need to take extra steps to protect themselves from harm.
  • If the day's air quality forecast is code orange or worse, adjust your plans for the day. Avoid long periods of activity outdoors. The health effects of pollution are worsened over extended periods of exposure, and by the deep, rapid breathing that comes with exercise. Stay away from high-traffic areas, and do not exercise near those areas. On really bad purple or maroon days everyone should try to stay indoors as much as possible. 
  • Speak out for healthy air. Let your local officials know that you are concerned about the effect air pollution may be having on your health and that you support stronger pollution control measures.

How Do You Find Air Quality Information?

  • You should be able to find information about the daily air quality index for your area wherever you get your weather forecast. Check your local radio, TV weather reports, newspaper or the weather app on your phone.
  • The EPA issues year-round AQI forecasts for most of the nation, including maps that show how pollution levels change and move throughout the day. It is "real-time" information, so you can see current outdoor air quality. The maps are available at Airnow.gov.  

Page last updated: November 2, 2023

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