This method is applicable to the determination of the pressure relief device (PRD) to use with compressed gas mixtures in cylinders having water capacities of less than or equal to 1000 lb (454 kg). This standard also applies to DOT 3AX, 3AAX, and 3T cylinders having water capacities greater than 1000 lb (454 kg) that comply with the specifications, charging, and maintenance regulations of DOT or the corresponding specifications and regulations of TC.

This method is limited to those compressed gas mixtures with known flammability, toxicity, state, and corrosivity. In addition, the DOT/TC rating and dimensions of the cylinder and the final pressure shall be known.

For the selection of PRDs for a single component compressed gas, see CGA S-1.1. For multicomponent compressed gases (mixtures), the method for selection of relief devices in this standard shall be used. Where a mixture is predominantly made up of a single component in a mixture, the gas producer shall determine whether the properties of this mixture dictate it being treated as a single component compressed gas or a gas mixture.