This standard represents the minimum requirements for pressure relief devices (PRDs) considered to be appropriate and adequate for use on cylinders with a water capacity less than or equal to 1000 lb (454 kg). Refer also to Title 49 of the U.S. Code of Federal Regulations (49 CFR), CSA B340, Selection and use of cylinders, spheres, tubes, and other containers for the transportation of dangerous goods, Class 2, and/or CSA B342, Selection and use of UN pressure receptacles, multiple-element gas containers, and other pressure receptacles for the transport of dangerous goods, Class 2. This standard also applies to composite overwrapped pressure vessels (COPVs), DOT-3AX, DOT-3AAX, and DOT-3T cylinders with a water capacity greater than 1000 lb (454 kg) as well as United Nations (UN) pressure receptacles with a water capacity up to 3000 kg, and which comply with the design specifications and charging (filling) and maintenance regulations of the U.S. Department of Transportation (DOT) or the corresponding specifications and regulations of Transport Canada (TC).

This standard applies to the selection of PRDs for a single component compressed gas in cylinders. For selection of PRDs for compressed gas mixtures in cylinders, see CGA S-7, Standard Method for Selecting Pressure Relief Devices for Compressed Gas Mixtures in Cylinders.

This standard does not cover PRD requirements for CTC/DOT-4L and TC-4LM insulated cylinders containing cryogenic liquids, see CGA S-1.2, Pressure Relief Device Standards—Part 2—Portable Containers for Compressed Gases. This standard does not cover PRD requirements for multi-unit tank car tanks (DOT106A/TC106A and DOT110A-W/TC110A), see 49 CFR 179.300-15 and CGSB 43.147, Construction, Modification, Qualification, Maintenance, and Selection and Use of Means of Containment for the Handling, Offering for Transport, or Transporting of Dangerous Goods by Rail, as appropriate.

This standard includes tables that provide information pertaining to PRDs. Table 1 contains information on the different types of PRDs. Table 2 provides a list of gases and their PRD assignments. Table 3 contains temperature correction factors. Table 4 includes values for basic orifice factors flange taps for flow in ft3/minute.

For PRD standards for bulk transport containers and stationary storage containers, see CGA S-1.2 and CGA S-1.3, Pressure Relief Device Standards—Part 3—Stationary Storage Containers for Compressed Gases.