Air Conditioning Terms

AIR CLEANING: An IAQ control strategy to remove various airborne particulates and/or gases from the air. The three types of air cleaning most commonly used are particulate filtration, electrostatic precipitation, and gas sorption.

AIR CONDITIONING: The simultaneous control of temperature, humidity and contamination to meet space requirements.

AIR EXCHANGE RATE: The rate at which outside air replaces indoor air in a space. Expressed in one of two ways: the number of changes of outside air per unit of time air changes per hour (ACH); or the rate at which a volume of outside air enters per unit of time - cubic feet per minute (cfm).

AIR HANDLING UNIT (AHU): For purposes of this document refers to equipment that includes a blower or fan, heating and/or cooling coils, and related equipment such as controls, condensate drain pans, and air filters (the indoor unit).

ANTIMICROBIAL: Agent that kills microbial growth.

CFM: Cubic feet per minute. The amount of air, in cubic feet, that flows through a given space in one minute. 1 CFM equals approximately 2 liters per second (l/s).

ENVIRONMENTAL TOBACCO SMOKE (ETS): Mixture of smoke from the burning end of a cigarette, pipe, or cigar and smoke exhaled by the smoker (also secondhand smoke (SHS) or passive smoking). 

Filter: A device used to remove dust and other particles from air for the purposes of reducing the load on the respiratory system and to protect the HVAC equipment. Filters vary greatly in particle arrestance; the higher the MERV rating, the better the filter.

FPM: Feet Per Minute. The velocity of air across a filter.

HEPA: High Efficiency Particulate Arrestance (filters).

HVAC: Heating, Ventilation, and Air Conditioning system.

IAQ: Indoor air quality.

INDOOR AIR POLLUTANT: Particles and dust, fibers, mists, bioaerosols, and gases or vapors.

Infiltration: Air flow into a space usually through walls and leaks around doors and windows.

PM: Preventive Maintenance.

Relative Humidity: The ratio of the amount of vapor contained in the air to the greatest amount the air could hold at that temperature. Normally expressed as a percentage.

Return Air: Air drawn into a heating unit after having been circulated from the heater's output supply to a room.

SICK BUILDING SYNDROME (SBS): Term that refers to a set of symptoms that affect some number of building occupants during the time they spend in the building and diminish or go away during periods when they leave the building. Cannot be traced to specific pollutants or sources within the building

Thermostat: A temperature control device, typically found on a wall inside that consists of a series of sensors and relays that monitor and control the functions of a heating and cooling system.

Tonnage: The unit of measure used in air conditioning to describe the cooling capacity of a system. One ton of cooling is based on the amount of heat needed to melt one ton (2000 lbs.) of ice in a 24 hour period. One ton of cooling is equal to 12,000 Btu/hr.

VOC’s: Volatile Organic Compounds are emitted as gases from certain solids or liquids. They are found in many indoor sources, including many common household products and building materials.

ZONE: The occupied space or group of spaces within a building which has its heating or cooling controlled by a single thermostat.