Supply air fans, intake fans, supply fan and make-up air blowers are used for specific situations where fresh and or clean make-up air needs to be replaced at a quicker rate than what would normally take place. If too much air is being exhausted from a space and the fresh air is not replaced quick enough, it can cause a negative pressure. Sometimes a particular static pressure must be present in the area to meet certain requirements. Applications include labs, hospitals, chemical plants, welding rooms, spray booth and more. Industrial Fans Direct can help you find the right air supply fan for your commercial or industrial needs.