49 CFR § 172.326 - Portable tanks.
(a)Shipping name. No person may offer for transportation or transport a portable tank containing a hazardous material unless it is legibly marked on two opposing sides with the proper shipping name specified for the material in the § 172.101 table. For transportation by vessel, the minimum height for a proper shipping name marked on a portable tank is 65 mm (2.5 inches); except that portable tanks with a capacity of less than 3,000 L (792.52 gallons) may reduce the marking size to not less than 12 mm (0.47 inches).
(1) If the identification number markings required by § 172.302(a) are not visible, a transport vehicle or freight container used to transport a portable tank containing a hazardous material must be marked on each side and each end as required by § 172.332 with the identification number specified for the material in the § 172.101 table.
(2) Each person who offers a portable tank containing a hazardous material to a motor carrier, for transportation in a transport vehicle or freight container, shall provide the motor carrier with the required identification numbers on placards, orange panels, or the white square-on-point configuration, as appropriate, for each side and each end of the transport vehicle or freight container from which identification numbers on the portable tank are not visible.
(d)NON-ODORIZED marking on portable tanks containing LPG. No person may offer for transportation or transport a portable tank containing unodorized liquefied petroleum gas (LPG) as authorized in § 173.315(b)(1) of this subchapter unless it is legibly marked NON-ODORIZED or NOT ODORIZED on two opposing sides near the marked proper shipping name required by paragraph (a) of this section, or near the placards. The NON-ODORIZED or NOT ODORIZED marking may appear on a portable tank used for both unodorized and odorized LPG.