The Air Quality Index Explained: What It Means and How to Stay Safe

Warmer temperatures and bright sun often bring along an unwanted guest: poor air quality.

A measure called the Air Quality Index gauges just how bad the air has become in a particular place. Readings of 100 or higher usually serve as a warning to people who have respiratory conditions to take precautions.

Having an understanding of the Air Quality Index can help you protect yourself from the harmful effects of air pollution. Here’s a guide to how it works.

What is the Air Quality Index?

The Air Quality Index measures the density of five pollutants in the air: ground-level ozone, particulates, carbon monoxide, nitrogen dioxide, and sulfur dioxide. It was established by the Environmental Protection Agency as a way to communicate to Americans the state of the air they are breathing each day. There are pollution monitors at more than 1,000 locations across the country.

How do you read the Air Quality Index?

The index runs from 0 to 500; the higher the number, the worse the air. If the index is registering less than 100, then the air pollution at that location is below the level known to cause adverse health effects.

When the index climbs above 100, the outdoor air may remain safe for many people, but older adults and children would be at some risk, as would people of any age with heart or lung disease. An. index number above 200 is considered “very unhealthy.”

Index readings fall into one of six color-coded categories; green represents the best conditions, yellow a bit less so, and orange, red, purple and maroon indicating progressively worse air.