The intent of this technical bulletin is to raise awareness within the compressed gas industry of the potential for the discharge of propylene from a CG-7 PRV if the 260 psi (18 bar) service pressure propylene cylinder and contents are exposed to elevated temperatures. This technical bulletin addresses CG-7 PRVs attached directly to the cylinder or as an integral part of the cylinder valve when used in propylene service and includes recommendations and requirements for the PRV start-to-discharge pressure for a 260 psi (18 bar) service pressure cylinder, seat materials, inspection and maintenance, activation indicators, and markings.This technical bulletin does not address PRV requirements for DOT-39 and TC-39M cylinders. It is beyond the scope of this technical bulletin to present detailed information on the storage, handling, and maintenance of the overall propylene cylinder package.