Is an AQI of 73 Bad? What Moderate Air Quality Means

If 73 is a U.S. Air Quality Index (AQI) reading, it falls in the Moderate range of 51–100—not the “Unhealthy” range. For most people, an AQI of 73 is generally acceptable for normal outdoor activities, though someone who is unusually sensitive to air pollution may want to ease up on prolonged, strenuous activity outside. We recommend reading the number alongside its label and pollutant, since a bare “73” on a monitor could represent a different measurement rather than AQI.

You usually do not need to stay inside solely because the outdoor AQI is 73, but you can adjust your plans if you notice symptoms or know that polluted air affects you. If you are planning a long run or outdoor work, look at the current reading and forecast before you go; conditions can change during the day. Our team also suggests paying attention to which pollutant is driving the reading, because a day with elevated ozone can call for different timing than a day with particle pollution.

On the U.S. AQI scale, 0–50 is Good, 51–100 is Moderate, 101–150 is Unhealthy for Sensitive Groups, and 151–200 is Unhealthy for everyone. That means 73 is below the level at which the AQI label advises sensitive groups to reduce prolonged or heavy outdoor exertion. If readings climb, you can shorten strenuous outdoor activities and move them indoors, especially if you have asthma or another condition that makes breathing more difficult.

Outdoor AQI does not tell you exactly what you are breathing indoors: cooking, smoke, cleaning products, and poor ventilation can affect individual rooms. When outdoor particle pollution rises, keeping windows closed can help limit what comes in, while using kitchen and bathroom exhaust ventilation for indoor moisture and cooking pollutants remains important. For a room-by-room starting point, you can read our Breathe Better Indoors, Live Better: A Practical Guide to Improving Indoor Air Quality.