[ A ]AbatementReduction or removal of a contaminant.Absolute HumidityIt is the ratio of the mass of water vapor to the unit volume of moist air represented in grams per cubic foot (g/ft3).Absolute ZeroTemperature at which all molecular motion ceases (-460 F. and -273 C.).Absorption RefrigeratorRefrigerator which creates low temperature by using the cooling effect formed when a refrigerant is absorbed by chemical substance.ACCAAir Conditioning Contractors of America – a leading HVAC/R Association.Acceptable indoor air qualityIndoor air that does not contain harmful concentrations of contaminants; air with which at least 80% of building occupants do not express dissatisfaction.AccumulatorStorage tank which receives liquid refrigerant from evaporator and prevents it from flowing into suction line before vaporizing. Tank on the suction side of a system that holds excess refrigerant to prevent slugging the compressor with liquid.ACHAir Changes Per Hour. The number of times that air in a house is completely replaced with outdoor air in one hour.Acid Condition In SystemCondition in which refrigerant or oil in system is mixed with fluids that are acid in nature.ACR TubingTubing used in air conditioning and refrigeration. Ends are sealed to keep tubing clean and dry.Activated CarbonSpecially processed carbon used as a filter drier ; commonly used to clean air.ActuatorThat portion of a regulating valve which converts mechanical fluid, thermal energy or electrical energy into mechanical motion to open or close the valve seats.Adiabatic CompressionCompressing refrigerant gas without removing or adding heat.Adjustable GrilleA grille with linear blades which can be adjusted to vary the direction of the discharged air. The linear blades are normally either vertical or horizontal, or both horizontal and vertical.AdsorbentSubstance with the property to hold molecules of fluids without causing a chemical or physical damage.AerationAct of combining substance with air.AFLU (Annual Fuel Utilization Efficiency)A rating that reflects the efficiency of a gas furnace in converting fuel to energy. A rating of 90 means that approximately 90% of the fuel is utilized to provide warmth to your home, while the remaining 10% escapes as exhaust.AFUE (Annual Fuel Utilization Efficiency)This number represents how efficiently a furnace converts fuel to energy. The ratio of annual output of useful energy or heat to the annual energy input to the furnace. The higher the AFUE, the more efficient the furnace — higher efficiency translates to more savings on fuel bills. This will range from 80% to 95%. Percentage of fuel used for heating. A measure of heating efficiency, in consistent units, determined by applying the federal test method for furnaces. This value is intended to represent the ratio of heat transferred to the conditioned space by the fuel energy supplied over one year.Air ConditionerDevice used to control temperature, humidity, cleanliness and movement of air in a confined space.Air ConditioningControl of the temperature, humidity, air movement and cleaning of air in a confined space.Air DiffuserAir distribution outlet or grille designed to direct airflow into desired patterns.Air Exchange RateThe 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 in 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 HandlerThe portion of the central air conditioning or heat pump system that moves heated or cooled air throughout a home’s ductwork. In some systems a furnace handles this function.Allergens and PathogensBiological material, including bacteria, viruses, fungi, mold spores, pollens, skin flakes and insect parts are ubiquitous in indoor environments. These particulates range from less than one to several microns in size. When airborne, they are usually attached to dust particulates of various sizes so that all sizes of airborne particulates may include them.AmbientThe surrounding atmosphere; encompassing on all sides; the environment surrounding a body but undisturbed or unaffected by it.Ambient AirThe air surrounding a building; outside air.Ambient Air TemperatureSurrounding temperature, such as the outdoor air temperature around a building.Ampere (A or Amp)The primary unit of measurement of electrical current. Amps multiplied by Volts determines Watts. Electricity bills are based on watts or kilowatts (a thousand watts) per hour.ARIAir-Conditioning and Refrigeration Institute is a nonprofit, voluntary organization comprised of heating,air conditioning and refrigeration manufacturers. ARI publishes standards for testing and rating heat pumps and air conditioners to provide you with a standardized measure of comparison. So, ARI ensures a level of performance within the industry.ASHRAEA leading HVAC/R Association – American Society of Heating, Refrigerating and Air Conditioning Engineers – http://www.ashrae.org/ The trade association that provides information and sets standards for the industry.ASTMAmerican Society for Testing and Materials.