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IAQ Glossary O


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OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION (OSHA): the regulatory arm of the US Department o f Labor, which promulgates safety and health standards, facilitates training programs, and enforces regulations on worksites. OSHA has developed permissible exposure limits (PELs) for over 600 contaminants present in the industrial workspace.

OCCUPIED ZONE: The region within an occupied space between planes 3 and 72 inches (75 and 1800 mm) above the floor and more than 2 feet (600 mm) from the walls or fixed air conditioning equipment (see ASHRAE Standard 55-1981).

OCTAVE BAND (O.B.): A range of frequency where the highest frequency of the band is double the lowest frequency of the band. The band is usually specified by the center frequency.

ODOR: A quality of gases, vapors, or particles which stimulates the olfactory organs; typically unpleasant or objectionable.

ODOR THRESHOLD: the lowest concentration of a chemical that can be reliably detected by a panel of untrained observers. Different investigators for many chemicals have reported variations of one to four orders of magnitude. This is due to differences in test methods, such as temperature and relative humidity control, and reporting methods.

OLF: (From "olfactory") A perceived air quality term which attempts to quantify a given pollution load. One person creates 1 olf of bioeffluents. If there are 10 cubic meters of floor space per person, then people create 0.1 olf per m² (olf/m²). Other sources are compared and quantified by olfs. For example, if 40% of the people smoke, this adds 0.2 olf/m² to the load.

OMNIVORE: Animal that obtains its nutrients from both plants and animals.

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OPERATIVE TEMPERATURE (to): The uniform temperature of a radiantly black enclosure in which an occupant would exchange the same amount of heat by radiation plus convection as in the actual non-uniform environment. Operative temperature is numerically the average, weighted by respective heat transfer coefficients (hc and hr), of the air (ta) and mean radiant temperatures (tr).
to = (hcta + hrtr)/hc+hr)
At air speeds of 80 fpm (0.4 m/s) or less and tr less than 120 F,(50oC) operative temperature is approximately the simple average of the air and mean radiant temperatures and equal to the adjusted dry bulb temperature.

OPTIMUM OPERATIVE TEMPERATURE: Temperature that satisfies the greatest possible number of people at a given clothing and activity level.

OUTDOOR AIR INTAKE: an opening in the building exterior that is a planned entry point for outdoor air.

OUTLET, CEILING: A round, square, rectangular, or linear air diffuser located in the ceiling, which provides a horizontal distribution pattern of primary and secondary air over the occupied zone and induces low velocity secondary air motion through the occupied zone.

OUTLET, SLOTTED: A long, narrow air distribution outlet, comprised of deflecting members, located in the ceiling sidewall, or sill, with an aspect ratio greater than 10, designed to distribute supply air in varying directions and planes, and arranged to promote mixing of primary air and secondary room air.

OUTLET, VANED: A register or grille equipped with vertical and/or horizontal adjustable vanes.

OUTLET VELOCITY: The average velocity of air emerging from the outlet measured in the plane of the outlet.

OUTPUT: Capacity, duty, performance, net refrigeration produced by system.

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OUTSIDE AIR OPENING: Any opening used as an entry for air from outdoors.

OZONE: a highly reactive trivalent form of oxygen. Ozone exposure can result in mucous membrane irritation and potential pulmonary damage. The principal source of indoor ozone is outdoor photochemical smog, although come copier machines and laser printers emit noticeable levels.

OZONE GENERATOR: an air cleaning device that produces highly reactive ozone, which reacts with volatile organic compounds to form non-hazardous products and reduces the number of bio-contaminants. these devices are controversial because their touted benefits may only be accomplished at ozone levels above recommended exposure levels.

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