Particle counters are used for checking contamination levels and locating sources of particle emissions at critical locations.

Medical industries use them to monitor air filter systems for microorganisms such as a bacterium or fungus particles. Filter manufacturers can test their filter effectiveness. Cleanroom industries can perform quick status checks of their clean rooms. HVAC personnel can determine indoor air quality quickly.

Biological contaminants include mold, fungus, bacteria, viruses, animal dander, dust mites, pollen, human skin cells, cockroach parts or anything alive or living at one time.  These are the biggest enemy of Indoor Air Quality specialists because they are the contaminants that cause health problems.  Levels of biological contamination depend on humidity and temperature that supports the livelihood of micro-organisms.  The presents of pets, plants, rodents and insects will raise the level of biological contamination.