Propane tanks need specific marking depending on whether they are stationary or being transported.

Propane tank marking requirements vary depending on the type of tank and whether or not it is transported. Any propane tank that is transported or mobile must follow the U.S. Department of Transportation (DOT) regulations for marking. This includes large storage tanks that otherwise conform to the American Society of Mechanical Engineers (ASME) standards. Otherwise, stationary storage tanks must follow the marking requirements set by the Boiler and Pressure Vessel Code.

Portable Cylinders

Portable propane cylinders, like those used for barbecue grills, are regulated by the DOT, and therefore must be marked according to their regulations. All DOT cylinders must include a label with a red diamond and the words "flammable gas", the symbol for flammability, and the number "2" at the bottom of the diamond, indicating the hazardous material class of propane. In addition, the number "1075", the hazardous material identification number for propane, must also be clearly marked on the label along with the words "liquefied petroleum gas", to comply with the NFPA code required by many local jurisdictions.

Storage Tanks

Stationary tanks for bulk storage, more commonly known as ASME containers, must be marked according to Boiler and Pressure Vessel Code, Section VIII. This code mandates that a metal data plate with specific information be attached to the tanks. The data plate must include the serial number, water capacity, maximum vapor pressure allowed, the manufacturer's name and address, various dimensions and whether the tank is designed for above ground or underground use.

During transport, ASME tanks must be marked and, if not visible from outside the vehicle, the vehicle placarded according to DOT regulations. The markings, similar to that for portable tanks, must include the number "1075", the hazardous material identification number for propane. The number "2", for the hazard class, or the number "2.1", to indicate the hazard class division, must also be visible on the label and/or placard. This information is to be, again, on a red diamond, with the 1075 either on the diamond or on a separate orange panel. In addition, vehicle mounted tanks must display a black diamond decal with "PROPANE" in white letters either near the access panel door, fender skirt or on the lower right rear near the bumper.

Requalification of Portable Tanks

Portable DOT cylinders must be re-qualified before reuse every five, seven or 12 years, depending on the method used for the last re-qualification. When re-qualified, the portable propane cylinders must be marked according to DOT regulations. The marking must be made permanent through stamping or engraving and must include the month and year of the re-qualification, the method used and the re-qualifier's identification number. These markings must also follow one of four patterns specified in the DOT regulations to prevent tampering or other misuse.