Supplied air respirators offer many features over traditional respiratory protection, such as cooling or heating incoming air with certain valves; fit testing only required for tight-fitting facepieces; and low maintenance. Complete systems include a supplied air hose, an air regulating valve, a breathing tube, and a helmet, hood, or other facepiece. 3M Supplied Air Respirators require a source of clean breathing air such as plant air systems or bottled air. This clean, breathable air can be delivered to hoods, helmets, full facepieces, half facepieces and loose-fitting facepieces.