Short for micrometer, a micron is one millionth of a meter and approximately 1/25,000th of an inch. Microns are used to measure airborne particle sizes. This is important because many harmful airborne particles are invisible to the naked eye, making them easily inhaled or distributed throughout your indoor environment.

For example, dust mite allergens can be as small as 0.1 to 0.3 microns, which is considerably smaller than a single strand of human hair that typically measures 30 to 120 microns.