With the first day of Summer quickly approaching, it is important to stay safe not only from the heat, but also from dangerous air pollutants. That is why the air quality index exists.

The air quality index (AQI) is a measurement established by the Environmental Protection Agency (EPA) that focuses primarily on the air quality content in the atmosphere. It is measured based on intervals of numbers, with 0-50 being labeled as “good” and 301 or higher being labeled as hazardous.

When the AQI is good, this means that air pollution in a given area poses little to no risk, even for the sensitive groups. Very sensitive groups may need to stay indoors when the index reaches the “moderate” level. An AQI ranging from 101 to 300 represents a more significant rise in the content of air pollutants. Health effects become more apparent at this stage for both sensitive and non-sensitive groups. When the index reaches over 300, a health warning of emergency conditions is released, and everyone is more likely to be affected when outdoors.

According to the EPA, the five major air pollutants to look out for while outdoors are ground-level ozone, particle pollution, carbon monoxide, sulfur dioxide, and nitrogen dioxide. Each of these pollutants has a national air quality standard set by the EPA to protect public health. Common health effects that can occur from exposure to air pollutants include headaches, asthma, irritated eyes, fatigue, and increased coughing. Before going outside, always check your local weather forecast for updates on the AQI for your area. Anything highlighted in orange, red, purple, or maroon means that limiting time outdoors is highly recommended.