ABSTRACT
Suitable technologies to compress breathing gas are essential to the conduct of underwater diving. Early ‘standard dress’ divers used simple hand pumps to provide a constant ow of compressed air to their helmets. Modern demand regulators used in both scuba diving and commercial surface-supply breathing apparatus (SSBA) require a supply of compressed gas at around 5 to 10 bar pressure that can be delivered either from the rst-stage regulator on a dive cylinder or from the surface via a diving umbilical hose. Compressors are therefore necessary either to supply breathing gas directly to the diver or to ll the dive cylinders.
