Google Maps on both iOS and Android has a new Air Quality layer that can be useful when planning your next hike or bike ride in good times, or to plan your escape from smog and smoke in bad.

The new layer displays an Air Quality Index (AQI) overlay directly onto the map grid using government data gathered from agencies like the EPA in the US to show how healthy the air is in general. Better yet, it also presents data collected from PurpleAir’s network of sensors to report hyperlocal conditions at the street level. Clicking on the AQI readings dotted around Google Maps provides more information on the health impact of the air quality, time and source of the last reading, and links to learn more.

PurpleAir’s relatively low-cost sensors measure particulates using laser particle counters. “You basically shine a laser through the air and then the particles in the air reflect the light and the detector picks up those reflections,” explained PurpleAir founder Adrian Dybwad to The Verge back in 2020, when his company’s sensors became a popular way to track the smoke produced by catastrophic wildfires raging across the West Coast. Last year Google Maps added a wildfire layer to track the growing threat.

Image: PurpleAir

In addition to PurpleAir, Breezometer is also in the business of mapping hyperlocal air quality. Cowboy e-bike owners have relied upon the company’s data to avoid pollution on their commutes since early last year. Breezometer, however, uses complex models — not physical sensors — to achieve a claimed data resolution of 5-meters (about 16 feet).