When we see the acronym HVAC, most only think of heating and air conditioning. But the V is for ventilation, an important role when considering the air quality in buildings. Indoor air quality is achieved through ventilating and filtering air in a space. The International Mechanical Code’s definition of ventilation is “The natural or mechanical process of supplying conditioned or unconditioned air to, or removing such air from, a space.” When we supply fresh air to spaces and remove stale air, we improve the breathing air quality for the occupants. When air is “conditioned”, it means several things that include removing or adding heat, cleaning the air, removing moisture, and replacing air.