49 CFR § 172.330 - Tank cars and multi-unit tank car tanks.
(1) In a tank car unless the following conditions are met:
(ii) A tank car containing any of the following materials must be marked on each side with the key words of the proper shipping name specified for the material in the § 172.101 table, or with a common name authorized for the material in this subchapter (e.g., “Refrigerant Gas”):
(b) A motor vehicle or rail car used to transport a multi-unit tank car 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.
(c) No person may offer for transportation or transport a tank car or multi-unit tank car tank containing unodorized liquefied petroleum gas (LPG) unless it is legibly marked NON-ODORIZED or NOT ODORIZED on two opposing sides near the marked proper shipping name required by paragraphs (a)(1) and (2) of this section, or near the placards. The NON-ODORIZED or NOT ODORIZED marking may appear on a tank car or multi-unit tank car tank used for both unodorized and odorized LPG.