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IAQ Glossary R


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RADIANT TEMPERATURE ASYMMETRY: The difference between the plane radiant temperature of the two opposite sides of a small plane element.

RADIATION, THERMAL: The transmission of heat through space by wave motion; the passage of heat from one object to another without warming the space between.

RADIUS OF DIFFUSION: The horizontal distance in feet from the diffuser to a point where the terminal velocity of 50 feet per minute occurs.

RASH: A skin swelling. Kinds of rashes are butterfly rash, diaper rash, drug rash, heat rash.

REACTIVATION: the removal of adsorbates from spent activated charcoal, which allows the carbon to be reused; also called regeneration.

RECIPROCATING: In refrigeration, a type of compressor which compresses refrigerant vapor by moving a piston up and down in a cylinder.

RECIRCULATED AIR: the return air that has been conditioned and returned to a given space.

REEINTRAINMENT: the attraction of contaminants exhausted from a building into the supply air stream by way outside air supply inlets or other routes of outside air infiltration, such as leaks, windows, doorways, elevators shafts, and stairways.

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REFRIGERANT: The fluid used for heat transfer in a refrigerating system, which absorbs heat at a low temperature and a low pressure of the fluid and rejects heat at a higher temperature and a higher pressure of fluid, usually involving changes of state of the fluid.

REGISTER: A grille which is equipped with a damper or control valve, and which directs air in a non-spreading jet.

REHEAT: a coil placed after the cooling coil, used to raise the air temperature; the process of raising the cooled air temperature. Used mainly with DX coil dehumidification.

RELATIVE HUMIDITY: The ratio of the quantity of water vapor present in the air compared to the quantity of water vapor present in saturated air at the same temperature and barometric pressure.

RELATIVE RISK: the ratio of health impact incidence among exposed individuals to incidence among unexposed individuals.

REPLACEMENT AIR: the air supplied to a space to replace exhausted air; compensating air, make up air.

RESERVOIR: the environmental substrate, or source, of a particular organism. Reservoirs for indoor biocontaminants include stagnant water, moist surfaces, and dust collection sites.

RESET: A process of automatically adjusting the control point of a given controller to compensate for changes in outdoor temperature. The hot deck control point is normally reset upward as the outdoor temperature drops. The cold deck control point is normally reset downward as the outdoor temperature increases.

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RESPIRABLE PARTICLES: Those particles in air which penetrate into and are deposited in the conciliated portion of the lung.

RESPIRABLE SIZE PARTICULATES: Particulates in the size range that permits them to penetrate deep into the lungs upon inhalation

RETURN: Any opening through which air is removed from a conditioned space.

RETURN AIR: Air returned from conditioned or refrigerated space.

REVERBERATION: The persistence of sound in an enclosed space after the sound source has stopped. In a reverberation room, it is characterized by the decay or dying away the sound.

REVERBERATION TIME: The reverberation time of an enclosed space is the number of seconds required, or that would be required were the decay rate to remain constant, for the sound pressure level to decrease by 60 decibels.

RHINITIS: an inflammation of the mucous membrane of the nose caused by an infection or exposure to an allergen.

RISER SHAFT: A vertical shaft designed to house electric cables, piping and ductwork.

ROOM CRITERIA CURVES (RC CURVES): Curves similar to NC curves that represent a close approximation to a well balanced, bland-sounding spectrum.

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ROOM DRY BULB: The actual temperature of the conditioned room or space as measured with an accurate thermometer.

ROOM VELOCITY: The residual air velocity level in the occupied zone of the conditioned space (e.g. 65, 50, 35 fpm).

ROTAMETER: A flow meter, consisting of a precision-bored, tapered, transparent tube with a solid float inside. Used for calibrating instruments.

RTC: room temperature catalyst; a catalyst that accelerates chemical reactions at room temperature rather than at the usually required higher temperatures

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