A substance with the ability
to absorb another substance.
- In physics, the taking up of light, heat, or other energy by
molecules. The absorbed energy is converted into heat.
Absorption in chemistry is the taking up of one substance by
another. For example, a gas such as oxygen may be absorbed, or
dissolved, in water. In the HVAC industry heat energy is
absorbed from the medium being cooled and transferred in the
- A shell device installed in the suction line of a HVAC system
to prevent liquids from entering the compressor.
- A processed carbon commonly used in air filters to clean the
- Active Cooling
- HVAC term for compressor driven air conditioning.
Air-Conditioning and Refrigeration Institute
AHRI is an industry trade association that develops standards for
measuring and certifying product performance. For instance, ARI
Standard 270 provides guidelines for establishing sound levels for
outdoor air-conditioning equipment.
- Air Balance
- HVAC term for distributing air through a system to precisely
match the required amount.
- Air Cleaning
- In HVAC 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 Conditioner
- A device used to control temperature and humidity of the air.
- Air Conditioning
- In HVAC the control of the quality, quantity, and
temperature-humidity of the air in an interior space.
- Air Diffuser
- HVAC term for an air distribution outlet, typically located in
the ceiling, which mixes conditioned air with room air.
- Air Exchange Rate
- In HVAC 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 Handler
- HVAC term for a fan-blower, heat transfer coil, and housing
parts of a system.
- Air Handling Unit (AHU)
- In HVAC 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. Does not
include ductwork, registers or grilles, or boilers and chillers.
- Air Infiltration
- The unwanted entrance of air due to leakage, temperature
difference, or wind.
- Air Passages
- Openings through or within walls, through floors and ceilings,
and around chimney flues and plumbing chases, that permit air to
move out of the conditioned spaces of the building.
- Air Retarder/Barrier
- A material or structural element that inhibits air flow into
and out of a building's envelope or shell. This is a continuous
sheet composed of polyethylene, polypropylene, or extruded
polystyrene. The sheet is wrapped around the outside of a house
during construction to reduce air in-and exfiltration, yet allow
water to easily diffuse through it.
- Air Standard
- HVAC term for air having a temperature of 68 degrees F (20
degrees C) and a relative humidity of 50% at 14.7 psia.
- Air to Air
- Where both the condensing and evaporating mediums are air.
- Air Vent
- HVAC term for a valve, either manual or automatic, that is
used to remove unwanted air from the highest point of a piping
- A substance capable of causing an allergic reaction because of
an individual's sensitivity to that substance.
- Ambient Air
- The air external to a building or device.
- The usually unfinished space above a ceiling and below a roof.
- Attic Fan
- A fan mounted on an attic wall used to exhaust warm attic air
to the outside.
- Attic Vent
- HVAC term for a passive or mechanical device used to ventilate
an attic space, primarily to reduce heat buildup and moisture
- Available Heat
- The amount of heat energy that may be converted into useful
energy from a fuel.