HVAC (pronounced either "H-V-A-C" or, occasionally, "H-VAK") is an initialism/acronym that stands for "heating, ventilating, and air conditioning". This is sometimes referred to as climate control. 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.

The HVAC industry is huge, worldwide, with career opportunities ranging from operation and maintenance, to system design and construction, to equipment manufacturing and sales, and to education and research. Annual sales are in the US$100's of billions. There are also hundreds of related local, national, and international professional, technical, trade, and labor organizations such as ASHRAE, SMACNA, ACCA, and AMCA, to name just a few, that support the industry and encourage high standards and achievement.

The three HVAC functions, heating, ventilating, and air-conditioning, are closely interrelated. All seek to provide thermal comfort, acceptable indoor air quality, and reasonable installation, operation, and maintenance costs. HVAC systems can provide ventilation, reduce infiltration, and maintain pressure relationships between spaces. How air is delivered to, and removed from spaces is known as room air distribution.[1]

In modern buildings the design, installation, and control systems of these functions are integrated into one or more HVAC systems. For very small buildings, contractors normally "size" and select HVAC systems and equipment. For larger buildings where required by law, "building services" designers and engineers, such as mechanical, architectural, or building services engineers analyze, design, and specify the HVAC systems, and specialty mechanical contractors build and commission them. In all buildings, building permits for, and code-compliance inspections of the installations are the norm.
http://en.wikipedia.org/wiki/HVAC

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Note added at 12 hrs (2007-01-13 07:20:42 GMT)
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