Back ARB Home

Air Tips

Ozone and particles 2.5 micrometers or smaller (PM2.5) are the two pollutants that most affect the air we breathe. High levels of ozone and particles can cause or worsen asthma and other cardiovascular diseases. Ozone is a gas that forms when sunlight combines with emissions from traffic and other human activities. Particle pollution may be emitted directly into the air or can form in the air from other emissions.

State and local agencies measure varying levels of these pollutants hourly at over 200 locations in California. The color indicators below are based on federal guidelines reflecting potential health impacts from pollutant exposure over extended time periods - 8 hours for ozone and 24 hours for particles. We suggest you check back frequently to track changes in hourly levels and help you better plan your daily outdoor activities.

When air quality is -

Green/Good: Enjoy your usual outdoor activities.
Yellow/Moderate: Extremely sensitive children and adults should refrain from strenuous outdoor activities.
Orange/Unhealthy for Sensitive Groups: Sensitive children and adults should limit prolonged outdoor activity.
Red/Unhealthy: Sensitive groups should avoid outdoor exposure and others should limit prolonged outdoor activity.
Purple/Very Unhealthy: Sensitive groups should stay indoors and others should avoid outdoor activity.
Back to Top