Abstract: A valve arrangement intended particularly, but not exclusively, for use with a breathing regulator (1) for underwater breathing apparatus includes an outlet side, an inlet (11) through which gas can pass to the outlet side from a source of gas having a pressure above atmospheric pressure, a movable valve means (12) which functions to close the gas inlet, and a servo device (21) for regulating the valve means. The servo device includes a servo housing (21) and two mutually joined arms (24, 26). The arms provide a lever effect whereby the supply of air can be controlled with great precision. The simplicity of the lever arrangement imparts a long useful life to the valve arrangement. A breathing regulator (1) which includes such a valve arrangement is preferably made essentially entirely from a plastic material.