HVAC

HVAC may also stand for High-voltage alternating current HVAC (pronounced either "H-V-A-C" or, occasionally, "aitch-vak") is an initialism/acronym that stands for "heating, ventilation, and air conditioning". HVAC is sometimes referred to as "climate control" and is particularly important in the design of medium to large industrial and office buildings such as sky scrapers and in marine environments such as aquariums, where humidity and temperature must all be closely regulated whilst maintaining safe and healthy conditions within. In certain regions (e.g., UK) the term "Building Services" is also used, but may also include plumbing and electrical systems.  Refrigeration is sometimes added to the field's abbreviation as HVAC&R or HVACR, or ventilation is dropped as HACR (such as the designation of HACR-rated circuit breakers).
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Heating Ventillation & Aircooling

the heating, ventilation, and air conditioning system of a building.