49 CFR §172.330

1. (a)Shipping name and identification number. No person may offer for transportation or transport a hazardous material—
   1. (1)In a tank car unless the following conditions are met:
      1. (i)The tank car must be marked on each side and each end as required by § 172.302 with the identification number specified for the material in the § 172.101 table; and
      2. (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”):
   2. (2)In a multi-unit tank car tank, unless the tank is marked on two opposing sides, in letters and numerals no less than 50 mm (2.0 inches) high—
      1. (i)With 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”); and
      2. (ii)With the identification number specified for the material in the § 172.101 table, unless marked in accordance with §§ 172.302(a) and 172.332 of this subpart.
2. (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.
3. (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.