Molds are microscopic organisms found virtually everywhere, both indoors and outdoors. Molds are tiny, lightweight and easily detached by airflow, vacuuming or walking on carpet. Indoors they grow in air-conditioning ducts, carpets, potted plants, etc. They produce and release millions of spores, which are small enough to stay airborne while threatening to invade the human respiratory system. In large quantities, molds can cause allergic symptoms similar to those caused by plant pollen.

Molds also produce microbial volatile organic compounds (MVOC’s). In commercial and professional settings, exposure to mold has been said to decrease work production by 2-4 %.