Fan filter unit

[3] FFUs are typically manufactured in 4' x 2', 3' x 2', or 2' x 2' steel housings, which can be placed in ceiling grid bays of similar dimensions.

A motorized fan is used to pull air through the filters for distribution to rooms or enclosed work stations such as hoods.

Depending on the cleanliness requirements of the controlled space, more fan filter units can be added to the grid in order to meet ISO standards for airflow velocity and air changes per hour.

[2] Additionally, when less than 20 filters are installed in a room, a fan- powered HEPA, FFU is generally considered to be less expensive than a more conventional ducted supply system.

[5] When a microenvironment of clean air is required, FFUs can be used to construct enclosed work spaces, or laminar flow cabinets.