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What is air quality index? Breaking down AQI alerts and what it means for your health

What is a "Code Red" air quality alert and how it impacts you
What is a "Code Red" air quality alert and how it impacts you 02:17

PHILADELPHIA (CBS) -- Air Quality Index (AQI) refers to the Environmental Protection Agency's scale regarding the health impact of air quality and pollution in the U.S., regulated under the Clear Air Act. Within this scale, the EPA established five major air pollutants, which have a national air quality standard in an effort to protect public health.

Millions of people in the U.S. live in areas where air pollution can cause serious health problems and the air quality can impact your daily life, according to AirNow.

The scale has six color-coded levels of concern and runs from 0 to 500 AQI value. Each code has a definitive "values of index" range and corresponds to different levels of health concerns. A higher AQI value indicates a greater level of air pollution and a greater health concern.

The five major pollutants include:

What is good air quality and what is bad air quality?

An AQI value of 50 or below is classified as "good air quality," according to health experts. Once the AQI index reaches 100 or above is when the air quality is considered unhealthy and may impact certain groups of people.

The Air Quality Index displayed on shows the levels of classification for air pollution.

Using the Air Quality Index

The Air Quality Index helps the public understand their local air quality and the associated health risks. You can find AQI forecasts on state and local agency websites, as well as AirNow. AirNow AQI provides quality control and national reporting consistency regarding current and forecasted quality maps for more than 500 U.S. cities, as well as historical data for U.S. embassies and consulates around the world. It also monitors fire conditions and smoke plumes, as well as air quality data from Canada and Mexico. provides an interactive map so you can take steps to protect your health.

What is "Code Green" air quality?

A "Code Green" values of index ranges from 0 to 50 and is considered "good" or "satisfactory." The air pollution poses little to no public health risk.

What is "Code Yellow" air quality?

A "Code Yellow" is "moderate," with a range of 51 to 100. While this level is considered acceptable, there may be a risk for some people, especially those who may be sensitive to air pollution. 

What is "Code Orange" air quality?

A "Code Orange" breaks the threshold of what is considered unhealthy air quality for sensitive groups, with a range from 100 to 150. This means some people with pre-existing health issues, including those with ashtma or heart disease, may be affected.  Seniors, young children and pregnant women are also included as part of sensitive groups. 

What is "Code Red" air quality?

A "Code Red" is issued when the AQI index is 151 to 200. At this level, the air quality is "unhealthy" for the general public and those with pre-existing health issues may experience more serious health effects. The health effects of poor air quality, especially at Code Red or higher, can include coughing, stinging eyes, a scratchy throat or runny nose.

RELATED: Pets and air quality: Dogs, cats with pre-existing conditions could be at higher risk, vet says

What is "Code Purple" air quality?

A "Code Purple" ranges from 201 to 300 AQI index and is considered public health alert. The air quality in this range is "very unhealthy" and the risks of health effects increase for everyone. Health experts recommend an N95 or KN95 mask in these conditions.

What is "Code Maroon" air quality?

A "Code Maroon" is the highest concern level. When the AQI index reaches 301 or higher, the air quality is "hazardous" and is a health warning of emergency conditions, as everyone is more likely to be affected. Under hazardous air conditions, avoid any outdoor activity, keep doors and windows closed, and avoid using fans that suck outdoor air into your home. If you have air conditioning or an air purifier, run it.

What is ground-level ozone pollution?

Ozone is a gas composed of three atoms of oxygen, and can be "good" or "bad" for your health and the environment depending on where it is where it is found, according to the EPA. A "good" ozone is called stratospheric ozone and naturally occurs in the upper atmosphere, forming a protective layer that shields us from the sun's harmful ultraviolet rays. A "bad" ozone is at the ground level and has harmful air pollutants. It can trigger a variety of health problems and its main ingredient is smog.

What is particle pollution (PM)?  

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PM stands for particulate matter, also known as particle pollution, and is made up of tiny pieces of solids or liquids that are found in the air, according to the CDC. 

Particular pollutants are inhalable particles, including dust, dirt, soot, smoke and drops of liquid. Some are large enough to be seen with the naked eye, while others can only be detected by using an electron microscope, the EPA says.

There are two types of particular matter: PM10 and PM2.5. 

PM10 particles generally have a diameter of 10 micrometers and smaller. This is typically dust or mold. 

PM2.5 are much finer particles, with a diameter of 2.5 micrometers or smaller, or about one-thirtieth the width of a strand of human hair.

PMs can be made up of hundreds of different chemicals and can come from a variety of sources, including fires, automobiles, construction sites, unpaved roads, fields and smokestacks. When inhaled, PMs can cause serious health problems including premature death in people with heart or lung disease, nonfatal heart attacks, irregular heartbeats, aggravated asthma and decreased lung function. It can also increase respiratory symptoms and irritate airways, causing coughing or difficulty breathing. 

Monitoring the AQI can help you reduce your exposure to particle pollution in an effort to protect yourself from the harmful effects, 

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