Abstract: In an improved diving helmet, or diving helmet assembly, of the type having a seal characterized as a flexible diaphragm, usually an annular diaphragm which seals about the diver's neck to close off the helmet and provide an interface between the water and the diver's breathing gas, improvements characterized as means associated with said flexible diaphragm for sensing changes in the physical position of said diaphragm caused by the differential pressure between said ambient water pressure and said helmet pressure, and actuating means responsive to said sensing means for opening and closing a valve to regulate helmet gas pressure. The said actuating means is located in said gas supply inlet for regulating the flow of breathing gas into the helmet or in said gas exhaust outlet for regulating the flow of exhaust gas from the helmet, or both, such that the ingress or egress of gas to or from the helmet is regulated and directly proportioned to the differential pressure sensed by the flexible diaphragm.

Abstract: A spring loaded accumulator is carried by a diver and is positioned within the gas circuit of a push-pull system wherein the diver is supplied with breathing gas from a remote source and exhaust gas is returned back to the source. The accumulator positioned in the return line reduces umbilical hose and pump capacity requirements. A regulator within the accumulator is positioned to limit the maximum differential pressure on the diver side of the return line.