U.S. NAVY SCUBA DIVING MARK VI SEMI CLOSED CIRCUIT APPARATUS TRAINING FILM 43364 NA

Dating to 1966, this U.S. Navy training film highlights the Mark VI semi-closed circuit apparatus and shows how it works, how it is used, and how it should be maintained. The Mark VI is a chest-mounted, two- bag, semiclosed-circuit Mk VI unit that was used from the 1960s to the 1980s by Navy divers and U.S. Navy SEALs. It used a mixture of nitrogen and oxygen and was known as semi-enclosed because some gas had to be exhausted to the sea as the diver did not metabolize the nitrogen. The Mark VI was pioneere