A gas regulator includes a delivery valve assembly having a delivery outlet and a delivery valve member engageable with the delivery outlet for controlling flow of a gas from a gas source. A timing gas chamber receives gas from the gas source. Gas pressure within the timing gas chamber controls the operation of the delivery valve member. An adjustment system controls the amount of time required for the gas to fill the timing gas chamber so as to control the length of time that the delivery valve assembly is opened to conserve gas. In other embodiments, a capacity adjustment system can adjust the capacity of a gas reservoir system.