ALE9821 / 9821 PUMP AMBIENT MODEL A-750 TWO Allegro Ambient Air Systems & Pumps One-Worker System The complete One-Worker System offers a very portable, lightweight air source for a single worker. It comes complete with a comfortable, full-facepiece, supplied air respirator, a 1/4 HP ambient air pump and 50' of breathing air hose. Two-Worker System Our Two-Worker System provides a portable air source for one or two respirator users. It also includes two full-facepiece, supplied air respirators, a 3/4 HP ambient air pump and two 50' hoses.Three-Worker system and pump are also available.