The U.S. Department of Transportation’s (DOT’s) Pipeline and Hazardous Materials Safety Administration (PHMSA) issued a safety advisory informing offerors, or anyone using a DOT Specification 39 (DOT-39) cylinder, that cylinders with an internal volume of 75 cubic inches (in)(1.23 L) or more should not be filled with liquefied flammable compressed gas.


The rupture or release of a liquefied flammable compressed gas from a DOT-39 cylinder with an internal volume exceeding 75 in3 is a safety concern that could result in extensive property damage, serious personal injury or even death. PHMSA issued the advisory, in part, to address confusion about the regulatory requirements for using DOT-39 cylinders for these gases.


Current regulations do not specify the 75 inlimitation as it pertains to liquefied flammable compressed gas. However, on July 26, 2016, PHMSA issued a Notice of Proposed Rulemaking (NPRM) that would explicitly extend the limit on the internal volume of DOT-39 cylinders to use with all liquefied flammable compressed gases. PHMSA is reviewing comments on the NPRM.


For more information on DOT’s efforts to improve hazardous materials safety and awareness, or to access U.S. Hazardous Materials Regulations, visit the PHMSA website at