Air Handling Unit (AHU) – Equipment that includes a blower or fan, heating and/or cooling coils, and related equipment such as controls, condensate drain pans, and air filters. Does not include ductwork, registers or grilles, or boilers and chillers.

Allergen – A substance, such as mold, that can cause an allergic reaction.

Antimicrobial – Agent that kills microbial growth (i.e., chemical or substance that kills mold or other organisms). See “Biocide” and “Fungicide.”

Biocide – A substance or chemical that kills organisms such as mold.

Biological Contaminants – 1) Living organisms, such as viruses, bacteria, or mold (fungi), 2) the remains of living organisms, or 3) debris from or pieces of dead organisms. Biological contaminants can be small enough to be inhaled, and may cause many types of health effects including allergic reactions and respiratory disorders.

Building Envelope – Elements of the building, including all external building materials, windows, and walls, that enclose the internal space.

Ceiling Plenum – Space between a suspended ceiling and the floor above that may have mechanical and electrical equipment in it and that is used as part of the air distribution system. The space is usually designed to be under negative pressure.

Fungi – A separate kingdom comprising living things that are neither animals nor plants. The kingdom Fungi includes molds, yeasts, mushrooms, and puffballs. In the mold course, the terms fungi and mold are used interchangeably.

Fungicide – A substance or chemical that kills fungi.

Heating, Ventilation, And Air-Conditioning System (HVAC) –  Ventilation systems within a building supplying conditioned air.

High Efficiency Particulate Air (HEPA) – Filter that has an efficiency of 99.97% in capturing particulates.

Hypersensitivity – Great or excessive sensitivity.


Microbial Volatile Organic Compound (mVOC) – A chemical made by mold that is a gas at room temperature and may have a moldy or musty odor.

Mold – A group of organisms that belong to the kingdom Fungi. In this course, the terms fungi and mold are used interchangeably.

Mycotoxin – A toxin produced by a mold.


Plenum – Air compartment connected to a duct or ducts.


Remediate – Fix or remove.

Spore – The means by which molds reproduce. Spores are microscopic. They vary in shape and range from 2 to 100 microns in size. Spores travel in several ways: passively moved by a breeze or water drop, mechanically disturbed (by a person or animal passing by), or actively discharged by the mold (usually under moist conditions or high humidity).

Toxigenic – Producing toxic substances.