Air Quality Index

What is the Air Quality Index?
The AQI is a numeric scale that translates ambient air pollutant concentrations into consistent, recognizable values independent of the specific pollutant. The AQI is the primary measure we use to communicate the healthiness of air to the public.
Is it better to have a low AQI or a high one?

The lower, the better. AQI values of 50 or lower are considered “good” and anything below 101 is considered healthy based on national standards. This chart shows each range.

What do the AQI colors mean?
The colors of the AQI offer a quick reference to residents who see an air quality forecast or alert. Each color lines up with a specific category based on health standards.
Who is considered to be sensitive to air pollution?
Orange (AQI 101-150) is unhealthy for sensitive groups.
• Young children, whose immune systems and lungs are still developing;
• The elderly, whose immune systems may be weakened; and
• Those with lung ailments such as asthma, emphysema and COPD, who could see symptoms worsen.

If you notice difficulty breathing or irritation on days in which air quality is considered poor, you may also be sensitive to air pollution.

How is AQI calculated?
Monitors throughout the District are constantly measuring the concentration of pollutants in the air. The EPA has developed a formula that translates those pollutant values into AQI values. This formula is revised as the EPA adopts revised health-based standards.
If the air is unhealthy, what should I do?
There are several ways to reduce your exposure to air pollution. Staying indoors with windows and doors closed is the best solution. If you need to be outdoors, avoid activities which will stress your lungs and cause you to breathe heavier, such as exercise and physical activity. HEPA filters are also useful to reduce particulate pollutants inside of homes. In any case of medical emergency, please call 9-1-1.
How can I find out the AQI?
The easiest way to remain aware of air quality is to sign up for alerts through EnviroFlash. You can choose at which level you will receive alerts or sign up for daily forecasts. Alerts and forecasts are sent via e-mail or text message.

You can also get current air quality conditions and forecasts at The widget can be found on the right side of the page.