Glossary of Mold Related Terms
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Select a letter:
OA
Outdoor Air
Occupied Zone
The region within an occupied space between planes 3 and 72 in. (75 and 1800 mm) above the floor and more than 2 ft (600mm) from the walls or fixed air-conditioning equipment.
Odor
A quality of gases, liquids, or particles that stimulates the olfactory organ or sense of smell.
Odor Character or Quality
The property of the odor sensation that permits a person to distinguish odors of different substances based on prior exposure.
Odor Descriptor
Adjective given to an odor such as "floral," "caramel," "putrid."
Odor Pervasiveness
The rate of decrease of odor perception associated with the decrease in odorant concentration.
Odor Threshold
Concentration of odorous air at which half of the judges in a panel detect the odor.
Odorant
A substance that stimulates the olfactory receptors.
Opacity
The amount of light obscured by particulate matter in the air.
Organic
1. Any compound containing carbon. 2. Substances derived from living organisms.
OSHA
Occupational Safety and Health Administration.
Outdoor Air
Air taken from the external atmosphere and, therefore, not previously circulated through the system.
Oxidation
A substance containing oxygen that reacts chemically to produce a new substance.
Oxidation
A reaction in which oxygen combines with another substance.
Ozone (O3)
A very reactive oxidant containing three atoms of oxygen.

