Understanding AQI Categories: A Simple Guide

The Air Quality Index (AQI) is a standardized system used to communicate daily air quality levels to the public. Developed by the U.S. Environmental Protection Agency (EPA), the AQI focuses on health effects that may be experienced within hours or days after exposure to polluted air. (epa.gov)

What Does the AQI Measure?

The AQI measures concentrations of five major air pollutants regulated by the Clean Air Act:

• Ground-level ozone (O₃)
• Particulate matter (PM₂.₅ and PM₁₀)
• Carbon monoxide (CO)
• Sulfur dioxide (SO₂)
• Nitrogen dioxide (NO₂)

Each pollutant has its own AQI scale, and the highest AQI value among them determines the overall AQI for the day. (airnow.gov)

AQI Categories and Their Health Implications

The AQI is divided into six categories, each corresponding to a different level of health concern:

1. Good (0–50): Air quality is satisfactory, and air pollution poses little or no risk.
2. Moderate (51–100): Air quality is acceptable; however, there may be a risk for some people, particularly those who are unusually sensitive to air pollution.
3. Unhealthy for Sensitive Groups (101–150): Members of sensitive groups may experience health effects; the general public is less likely to be affected.
4. Unhealthy (151–200): Everyone may begin to experience health effects; members of sensitive groups may experience more serious effects.
5. Very Unhealthy (201–300): Health alert: everyone may experience more serious health effects.
6. Hazardous (301 and higher): Health warning of emergency conditions: everyone is more likely to be affected.

These categories are color-coded to make it easier for the public to understand the air quality at a glance. (airnow.gov)

How to Use the AQI

Monitoring the AQI can help you make informed decisions about outdoor activities:

• Good (0–50): Ideal for all outdoor activities.
• Moderate (51–100): Suitable for most outdoor activities; sensitive individuals may want to limit prolonged exertion.
• Unhealthy for Sensitive Groups (101–150): Sensitive individuals should limit prolonged exertion; others can continue normal activities.
• Unhealthy (151–200): Everyone should limit prolonged exertion; sensitive individuals should avoid outdoor activities.
• Very Unhealthy (201–300): Everyone should avoid outdoor activities.
• Hazardous (301 and higher): Everyone should avoid all outdoor activities.

By understanding AQI categories, you can take appropriate actions to protect your health and enjoy outdoor activities safely.

Highlights:

• Air Quality Index (AQI) - What It Means For You - YouTube, Published on Wednesday, February 08