What is the difference between an advisory and an alert?

An Advisory is called when two or more (or widespread) monitors are expected to reach or exceed the Unhealthy for Sensitive Groups (USG, Orange air quality index (AQI) threshold. The Advisory is designed to raise awareness for those who are particularly sensitive to USG level Fine Particulate (PM2.5) levels, along with raising awareness for those who are not directly affected but could still take action to help lower the overall pollution levels.

An Alert is called when two or more (or widespread) monitors are expected to reach or exceed the Unhealthy threshold. The Alert range is for Unhealthy (Red AQI), Very Unhealthy (Purple AQI), and Hazardous (Maroon AQI) pollution thresholds. The Alert is designed to raise heightened awareness because all health groups are included, can be affected, and should take action to help protect themselves. The Alert is not designed to negate the AQI categories/thresholds as there is different messaging within said thresholds. The Alert will include the expected AQI Categories to help people understand forecasted pollution levels.

An advisory or alert may be called for ozone, particulate matter, or both.

The Air Quality Index:

The Air Quality Index, or AQI, provides a color-coded framework for residents to see the levels of some types of air pollution in their area. The higher the AQI, the worse the air quality and the more cause for concern.

Currently, the AQI for particulate matter (PM) is high in many parts of Michigan due to smoke and fires in the U.S. and in parts of Canada. The AQI is used for ground-level ozone and particulates.