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Understanding AQI Categories and Exercise Safety

June 17, 2026 · The Clime Team
Understanding AQI Categories and Exercise Safety

The Air Quality Index (AQI) is a standardized system used to communicate the quality of air and its potential health effects. Understanding AQI categories is crucial for making informed decisions about outdoor activities, especially exercise.

What Is the AQI?

The AQI is a scale from 0 to 500 that measures the concentration of five major air pollutants: ground-level ozone, particulate matter (PM2.5 and PM10), carbon monoxide, sulfur dioxide, and nitrogen dioxide. Each pollutant has its own AQI scale, and the highest value among them determines the overall AQI for a location. The higher the AQI value, the greater the level of pollution and the greater the health concern. (airnow.gov)

AQI Categories and Their Implications

The AQI is divided into six categories, each corresponding to a different level of health concern:

  • 0 to 50 (Good): Air quality is satisfactory, posing little or no risk.
  • 51 to 100 (Moderate): Air quality is acceptable; however, there may be some health concern for a small number of unusually sensitive individuals.
  • 101 to 150 (Unhealthy for Sensitive Groups): Sensitive individuals may experience health effects; the general public is less likely to be affected.
  • 151 to 200 (Unhealthy): Everyone may begin to experience health effects; sensitive groups may experience more serious effects.
  • 201 to 300 (Very Unhealthy): Health alert: everyone may experience more serious health effects.
  • 301 and above (Hazardous): Health warning of emergency conditions; the entire population is more likely to be affected. (airnow.gov)

Exercise Recommendations Based on AQI Levels

Engaging in physical activity during periods of poor air quality can lead to adverse health effects, particularly for sensitive individuals. Here are general guidelines:

  • 0 to 50 (Good): Unrestricted outdoor exercise is safe for everyone.
  • 51 to 100 (Moderate): Most individuals can exercise outdoors without issues. Sensitive individuals should monitor for any symptoms and consider reducing intensity if necessary.
  • 101 to 150 (Unhealthy for Sensitive Groups): Sensitive individuals should reduce the duration and intensity of outdoor activities. Others can continue exercising but should be aware of any symptoms.
  • 151 to 200 (Unhealthy): Everyone should reduce prolonged or intense outdoor exercise. Sensitive individuals should consider moving activities indoors or rescheduling.
  • 201 to 300 (Very Unhealthy): Sensitive individuals should avoid all outdoor physical activity. Others should avoid long or intense exertion and consider staying indoors.
  • 301 and above (Hazardous): Everyone should avoid all outdoor physical activity. Sensitive individuals should remain indoors and keep activity levels low. (airnow.gov)

Protecting Your Health During Exercise

To safeguard your health during outdoor activities, consider the following:

  • Check the AQI: Before planning outdoor exercise, consult the AQI for your area. Websites and mobile apps provide real-time AQI updates.
  • Limit Intensity and Duration: On days with higher AQI levels, reduce the intensity and duration of your workouts.
  • Choose Indoor Alternatives: When the AQI is in the unhealthy range, opt for indoor exercise options.
  • Stay Informed: Stay updated on local air quality conditions, especially during events like wildfires or high-ozone days.

Conclusion

Understanding AQI categories is essential for making informed decisions about outdoor exercise. By monitoring air quality and adjusting your activities accordingly, you can protect your health while maintaining an active lifestyle.

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