sentences:  They produce various models of diving helmets, and related diving gear, and represent Viking Dry Suits, Composite Beat Engel DeepSea helmets, and Broco Welding.The DESCO "air hat", introduced in 1968, is still manufactured and is popular among air divers and particularly those working in contaminated environments; its free-flow, positive-pressure design affords an extra safety margin when contaminants are present.As compared to demand helmets, the air hat is simple and inexpensive to operate and maintain.