What is a DOT cylinder?
A DOT cylinder is a portable propane tank that meets U.S. Department of Transportation safety and design standards for containing and transporting liquefied petroleum gas at pressure.
The Department of Transportation (DOT) certifies and regulates portable propane cylinders to ensure they safely contain pressurized liquefied petroleum gas. Common sizes include 20-pound tanks used for outdoor grills, forklifts, and small appliances, as well as larger 30, 40, and 100-pound cylinders for commercial use. Each DOT cylinder bears a metal stamp on the collar showing the manufacturer's name, capacity, test date, and retest interval, usually 5 or 12 years depending on the cylinder type and inspection method.
Checking the stamped date code is critical because propane suppliers in Florida are required to refuse service to cylinders that have exceeded their recertification interval. A cylinder marked "12/21" with a 5-year retest interval, for example, expires in December 2026. Before that date, the owner must either have the cylinder professionally hydrostatic tested and recertified by a qualified facility, or exchange it for a compliant one. Propane suppliers and refill providers routinely check these stamps during transactions to verify compliance. Non-compliant cylinders pose safety and legal liability risks because they may have internal corrosion or structural weakness that pressurized gas could exploit. Understanding DOT markings and recertification timelines helps customers maintain safe, legal propane storage.