Now on to size. The “10” and the “2.5” refer to microns (AKA micrometers). Microns are tiny. Here’s an idea of how small microns are compared to human hair:
Next there’s a hidden (unlabelled) detail in the terms “PM10” and “PM2.5.” That is the “smaller than” piece. Each pollutant type is defined as that size and below. So PM10 is particles 10 microns and below. PM2.5 is 2.5 microns and below. (That means PM10 includes PM2.5.)
What PM Is Not
Finally, it’s helpful to think of what PM is not. Particulate pollution does not include gas pollutants like ozone and NO2.
Thomas is an Associate Professor of Behavior Science at the University of Chicago Booth School of Business and the founder of Smart Air, a social enterprise to help people in China breathe clean air without shelling out thousands of dollars for expensive purifiers.
Smart Air is a social enterprise based in China, India, Mongolia and the Philippines that creates simple, no-nonsense air purifiers and provides free education to combat the impacts of air pollution.
More about who the heck we are.