The air changes required must conform to the local health department code covering the type of installation. If no code requirements have to be met, a standard reference table for air changes is used.

Equipment selection will depend upon the structure to be ventilated and the coverage required to eliminate all dead air space. The second major determinant is the function that the space serves. A storage area where personnel rarely enters will have ventilation requirements different from that of a large manufacturing area.

Usually fans are installed opposite the prevailing wind to obtain maximum efficiency from the fan. The fan should also be installed opposite the intake to take full advantage of air movement over the entire area. Ventilators should be located on the roof to give a complete sweep of air movement over the area to be ventilated. Of course, local climate must also be considered when choosing equipment. Acceptable noise levels of the ventilation system will play a role in system design as well.