PHMSA is issuing this safety advisory notice to inform offerors and users of DOT Specification 39 (DOT-39) cylinders that DOT-39 cylinders with an internal volume exceeding 75 cubic inches (in\3\) (1.23 L) should not be filled with liquefied flammable compressed gas. PHMSA maintains filling or transporting DOT-39 cylinders with an internal volume exceeding 75 in\3\ (1.23 L) is not safe. POC is Refaat Shafkey, General Engineer, Engineering and Research Division, Office of Hazardous Materials Safety, Pipeline and Hazardous Materials Safety Administration, U.S. Department of Transportation, 1200 New Jersey Ave. SE., Washington, DC 20590. Tel: (-202-366-4545 or, via email: refaat.shafkey@dot.gov (Federal Register; 13 December 2016 [Notices], pages 90061-90062).