A micron is a unit of measurement that is 1/25,000 of an inch. 99% of the particles in the air are smaller than 1 micron. Because they are so small, they remain airborne.
Household dust is present even in clean homes and can be composed of mould spores, bacteria, viruses, animal dander, human skin particles, fabric fibers, dust mites, parts of cockroaches, food particles and other debris. About 2,000 microns of matter will fit across the diameter of a pin head!
Human hair Size: About 80-100 microns
Pollen Size: 30 microns
Household dust Size: 10 microns
Pet dander Size: 5 microns
Smoke particles Size: 1 micron