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 red" 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 ash, vehicle exhaust, soil dust, pollen, and other pollution). Newspapers, radio, television, and Web sites report AQI levels year-round. Keeping track of the current air quality information can help you take steps to protect yourself, children, and others from unhealthy levels of air pollution. 

Why should I pay attention to the Air Quality Index?

Air pollution can harm anyone, but it can be really dangerous for a lot of people, including: children and teens, people with asthma and other lung diseases, anyone over 65, anyone who exercises or works outdoors or has diabetes or cardiovascular disease like high blood pressure, or has suffered a heart attack or stroke.  Even healthy adults who exercise or work outdoors can be harmed. Changing what you do on these bad air days can reduce your risk of being harmed.  

How Does the Air Quality Index Work?

In over 900counties across the nation, 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 immediate danger to the public. The AQI further breaks air pollution levels into five categories, each of which has a name, an associated color, and advice to go along with it.

Index Value




0 to 50




51 to 100



Unusually sensitive individuals should consider limiting prolonged outdoor exertion

101 to 150

Unhealthy for Sensitive Groups


Children, active adults, and people with respiratory disease, such as asthma, should limit prolonged outdoor exertion

151 to 200



Children, active adults, and people with respiratory disease, such as asthma, should avoid prolonged outdoor exertion; everyone else should limit prolonged outdoor exertion

201 to 300

Very Unhealthy


Children, active adults, and people with respiratory disease, such as asthma, should avoid outdoor exertion; everyone else should limit outdoor exertion






Everyone should avoid all physical activity outdoors. 


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 to air pollution? Children and teens, the elderly, people with breathing problems including asthma, people with cardiovascular diseases or diabetes, and adults who are active outdoors, including outdoor workers and healthy exercisers, are all at higher risk. 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 level is orange or worse, adjust your plans for the day. Avoid prolonged vigorous activity outdoors. The health effects of pollution are worsened over extended periods of exposure, and by the deep, rapid breathing that accompanies exercise. Stay away from high-traffic areas, and do not exercise near those areas.
  • 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?

  • Air quality forecasts may be included as part of your local weather forecast on TV and radio or printed in the newspaper. If it is not available, call your local media and tell them you would like them to offer this important public health service.
  • State and local air pollution control agencies collect air quality data and report the AQI. You can call or email them for current information if it is not available through the media. A directory is available from the National Association of Clean Air Agencies, their national membership association, at Some offer air quality forecasts by email or text message.
  • 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 The EPA also makes it available to local weather forecasters through national weather service providers. You can sign up there to get air quality forecasts emailed to you or sent to your mobile phone.