49 CFR § 172.328 - Cargo tanks.
(a) Providing and affixing identification numbers. Unless a cargo tank is already marked with the identification numbers required by this subpart, the identification numbers must be provided or affixed as follows:
(1) A person who offers a hazardous material to a motor carrier for transportation in a cargo tank shall provide the motor carrier the identification numbers on placards or shall affix orange panels containing the required identification numbers, prior to or at the time the material is offered for transportation.
(2) A person who offers a cargo tank containing a hazardous material for transportation shall affix the required identification numbers on panels or placards prior to or at the time the cargo tank is offered for transportation.
(3) For a cargo tank transported on or in a transport vehicle or freight container, if the identification number marking on the cargo tank required by § 172.302(a) would not normally be visible during transportation—
(i) The transport vehicle or freight container must be marked as required by § 172.332 on each side and each end with the identification number specified for the material in the § 172.101 table; and
(ii) When the cargo tank is permanently installed within an enclosed cargo body of the transport vehicle or freight container, the identification number marking required by § 172.302(a) need only be displayed on each side and end of a cargo tank that is visible when the cargo tank is accessed.
(b) Required markings: Gases. Except for certain nurse tanks which must be marked as specified in § 173.315(m) of this subchapter, each cargo tank transporting a Class 2 material subject to this subchapter must be marked, in lettering no less than 50 mm (2.0 inches), on each side and each end with—
(1) The proper shipping name specified for the gas in the § 172.101 table; or
(2) An appropriate common name for the material (e.g., “Refrigerant Gas”).
(c) QT/NQT markings. Each MC 330 and MC 331 cargo tank must be marked near the specification plate, in letters no less than 50 mm (2.0 inches) in height, with—
(1) “QT”, if the cargo tank is constructed of quenched and tempered steel; or
(2) “NQT”, if the cargo tank is constructed of other than quenched and tempered steel.
(d) After October 3, 2005, each on-vehicle manually-activated remote shutoff device for closure of the internal self-closing stop valve must be identified by marking “Emergency Shutoff” in letters at least 0.75 inches in height, in a color that contrasts with its background, and located in an area immediately adjacent to the means of closure.
(e) NON-ODORIZED marking on cargo tanks containing LPG. No person may offer for transportation or transport a cargo 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 as specified in paragraph (b)(1) of this section, or near the placards. The NON-ODORIZED or NOT ODORIZED marking may appear on a cargo tank used for both unodorized and odorized LPG.