Air Quality Guide for Ozone

Ground-level ozone is one of our nation’s most common air pollutants. Use the chart below to help reduce your exposure and protect your health. For your local air quality, visit www.airnow.gov

View or print guide in PDF (2 pp., 70KB, about PDF) Updated March 2015


Air Quality Index (0-500) Who Needs to be Concerned? What Should I Do?
Good

(0-50)
No one. It’s a great day to be active outside!
Moderate
(51-100)

Some people who may be unusually sensitive to ozone. Unusually sensitive people: Consider reducing prolonged or heavy exertion. Watch for symptoms such as coughing or shortness of breath. These are signs to take it a little easier.

Everyone else: It’s a good day to be active outside!
Unhealthy for Sensitive Groups

(101-150)
Sensitive groups include people with heart or lung disease, older adults, children and teenagers, and people who are active outdoors. Sensitive groups: Reduce prolonged or heavy exertion. Take more breaks, do less intense activities. Watch for symptoms such as coughing or shortness of breath. Schedule outdoor activities in the morning when ozone is lower.

People with asthma should follow their asthma action plans and keep quick relief medicine handy.
Unhealthy

(151 to 200)
Everyone Sensitive groups: Avoid prolonged or heavy outdoor exertion. Schedule outdoor activities in the morning when ozone is lower. Consider moving activities indoors. People with asthma, keep quick-relief medicine handy.

Everyone else: Reduce prolonged or heavy outdoor exertion. Take more breaks, do less intense activities. Schedule outdoor activities in the morning when ozone is lower.
Very Unhealthy Alert

(201-300)
Everyone Sensitive groups: Avoid all physical activity outdoors. Move activities indoors or reschedule to a time when air quality is better. People with asthma, keep quick-relief medicine handy.

Everyone else: Avoid prolonged or heavy outdoor exertion. Schedule outdoor activities in the morning when ozone is lower. Consider moving activities indoors.
Hazardous

(301-500)
Everyone Everyone: Avoid all physical activity outdoors.

Sensitive groups: Remain indoors and keep activity levels low. Follow tips for keeping particle levels low indoors.

Note: If you don't have an air conditioner, staying inside with the windows closed may be dangerous in extremely hot weather. In these cases, seek alternative shelter.

Key Facts to Know About Ozone:

  • Ozone in the air we breathe can cause serious health problems, including breathing difficulty, asthma attacks, lung damage, and early death.

  • Ozone forms in the sun, usually on hot summer days. Ozone is worse in the afternoon and early evening, so plan outdoor activities for the morning.

  • You can reduce your exposure to ozone and still get exercise! Use the Air Quality Index (AQI) at www.airnow.gov to plan your activity.

What is ozone?

Ozone is a colorless gas that can be good or bad, depending on where it is. Ozone in the stratosphere is good because it shields the earth from the sun’s ultraviolet rays. Ozone at ground level, where we breathe, is bad because it can harm human health.

Ozone forms when two types of pollutants (VOCs and NOx) react in sunlight. These pollutants come from sources such as vehicles, industries, power plants, and products such as solvents and paints.

Why is ozone a problem?

Ozone can cause a number of health problems, including coughing, breathing difficulty, and lung damage. Exposure to ozone can make the lungs more susceptible to infection, aggravate lung diseases, increase the frequency of asthma attacks, and increase the risk of early death from heart or lung disease.

Do I need to be concerned?

Even healthy adults can experience ozone’s harmful effects, but some people may be at greater risk. They include:

  • People with lung disease such as asthma
  • Children, including teenagers, because their lungs are still developing and they breathe more air per pound of body weight than adults
  • Older adults
  • People who are active outdoors, including outdoor workers

How can I protect myself?

Use the Air Quality Index (AQI) to plan outdoor activities. To keep the AQI handy, sign up for EnviroFlash emails, get the free AirNow app, or install the free widget on your website. Find all of these tools at www.airnow.gov.

Stay healthy: exercise, eat a balanced diet, and keep asthma under control with your asthma action plan.

When you see that the AQI is unhealthy, take simple steps to reduce your exposure:

  • Choose a less-strenuous activity
  • Take more breaks during outdoor activity
  • Reschedule activities to the morning or to another day
  • Move your activity inside where ozone levels are usually lower

Can I help reduce ozone?

Yes! Here are a few tips.

  • Turn off lights you are not using
  • Drive less: carpool, use public transportation, bike or walk
  • Keep your engine tuned, and don’t let your engine idle
  • When refueling: stop when the pump shuts off, avoid spilling fuel, and tighten your gas cap
  • Inflate tires to the recommended pressure
  • Use low-VOC paint and cleaning products, and seal and store them so they can’t evaporate
  • Watch for Air Quality Action Days in your area

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US EPA Office of Air and Radiation
EPA-456/F-15-002
March, 2015

This page was last updated on Friday, March 13, 2015