HVAC (pronounced either "H-V-A-C" or "H-vak") is an initialism or 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 sites and office building such as skyscrapers, and in marine environments such as aquariums, where humidity and temperature must all be closely regulated whilst maintaining safe and healthy conditions within.