Section 58.16-15 - Valves and safety relief devices(a) Each cylinder must have a manually operated screw-down shutoff valve fitted with a handwheel installed directly at the cylinder outlet.(b) All cylinders must be protected by one or more safety relief devices complying with the requirements of § 58.16-10(a) . The safety relief device must be a shutoff valve with an integral spring-loaded safety relief valve and supplementary fusible plug, the latter designed to yield when the cylinder has been emptied of liquid gas by the relief valve under conditions of exposure to excessive heat.(c) Cylinder valves and safety relief devices must have direct communication with the vapor space of the cylinder.(d) In addition to the cylinder valve, a multiple cylinder system must be provided with a two-way positive shutoff manifold valve of the manually operated type. The manifold valve must be so arranged that the replacement of empty cylinders can be made without shutting down the flow of gas in the system.(e) A master packless shutoff valve controlling all burners simultaneously must be installed at the manifold of all gas-consuming appliances.