The Air Quality Index (AQI) is a standard set by the EPA for reporting air quality of five major pollutants that are regulated by the Clean Air Act. These pollutants are: Ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide.

More information about the Air Quality Index can be found here.

The Air Quality Index (AQI) is an index from 0 to 500. The higher the AQI value, the greater the level of air pollution and the greater the health concern. For example, an AQI value of 50 represents good air quality with little or no potential to affect public health, while an AQI value over 300 represents air quality so hazardous that everyone may experience serious effects.

An AQI value of 100 generally corresponds to the national air quality standard for the pollutant, which is the level EPA has set to protect public health. AQI values at or below 100 are generally thought of as satisfactory. When AQI values are above 100, air quality is considered to be unhealthy—at first for certain sensitive groups of people, then for everyone as AQI values increase.

A complete writeup on the Air Quality Index can be found here.

Ozone (O3) is a gas composed of three atoms of oxygen. Ozone occurs both in the Earth's upper atmosphere and at ground level. Ozone can be good or bad, depending on where it is found.

Ozone at ground level is a harmful air pollutant, because of its effects on people and the environment, and it is the main ingredient in “smog."

More complete information about ground level ozone can be found here.

Particulate Matter, commonly referred to as PM, is a mixture of solid particles and liquid droplets found in the air. Some particles, such as dust, dirt, soot, or smoke, are large or dark enough to be seen with the naked eye. Others are so small they can only be detected using an electron microscope.

More information about the sources of PM and the health effects can be found here.

An Action Day for fine particulate matter (PM), carbon monoxide (CO), ozone (O3), or other pollutants indicates that either current air quality is unhealthy or conditions are expected to worsen later in the day.

More information here.

There are many ways that you can help to reduce air pollution. Some tips include:

• Conserve energy at home and work
• Carpool, bike, or walk whenever possible
• Keep engines properly tuned and tires properly inflated
• Use environmentally safe paints and cleaning products
• Mulch or compost leaves and yard waste
• Avoid gas powered lawn and garden equipment

More ideas can be found here.

When AQI levels are hazardous, reduce activity levels to reduce the amount of particulates that you breathe into your lungs, and stay indoors in a room or building with filtered air.

A complete description of steps you should take, especially for at-risk groups, can be found here.