A unit of measure for the smallest of the small, One Micron is 0.001 mm or 0.00004 inch.
A micron is really, really small. The width of a human hair is about 70 microns. Our eyes can see no smaller than 40 microns, and you’ll need a decent microscope to see a particle 20 microns wide. Allergens like dust, smoke and bacteria are particulates that are often .3 microns or less. At that size, they can get deep into your lungs, because they aren’t filtered well by your nose and throat. If you’re concerned about controlling those airborne particulates, it’s good for you to know that Trane CleanEffects™ removes 99.98% of particulates, all particulates, from the air inside your home.