49 CFR § 173.25 - Authorized packagings and overpacks.
(2) The overpack is marked with the proper shipping name and identification number, when applicable, and is labeled as required by this subchapter for each hazardous material contained therein, unless marking and labels representative of each hazardous material in the overpack are visible.
(3) Each package subject to the orientation marking requirements of § 172.312 of this subchapter is packed in the overpack with its filling holes up and the overpack is marked with package orientation marking arrows on two opposite vertical sides of the overpack with the arrows pointing in the correct direction of orientation.
(4) The overpack is marked with the word “OVERPACK” when specification packagings are required, or for Class 7 (radioactive) material when a Type A, Type B(U), Type B(M) or industrial package is required. The “OVERPACK” marking is not required when the required markings representative of each package type contained in the overpack are visible from outside of the overpack. The lettering on the “OVERPACK” marking must be at least 12 mm (0.5 inches) high. For domestic transportation, an overpack marked prior to January 1, 2017, and in conformance with the requirements of this paragraph in effect on December 31, 2014, may continue in service until the end of its useful life.
(6) For limited quantities and ORM material, the overpack is marked with a limited quantity marking prescribed in § 172.315 of this subchapter or, the ORM marking prescribed in § 172.316 of this subchapter, unless a limited quantity or ORM marking representative of the hazardous material in the overpack is visible.
(b) Shrink-wrapped or stretch-wrapped trays may be used as outer packagings for inner packagings prepared in accordance with the limited quantity provisions or consumer commodity provisions of this subchapter, provided that—
(1) Inner packagings are not fragile, liable to break or be easily punctured, such as those made of glass, porcelain, stoneware or certain plastics; and
(2) Each complete package does not exceed 20 kg (44 lbs) gross weight.
(c) Hazardous materials which are required to be labeled POISON may be transported in the same motor vehicle with material that is marked or known to be foodstuffs, feed or any edible material intended for consumption by humans or animals provided the hazardous material is marked, labeled, and packaged in accordance with this subchapter, conforms to the requirements of paragraph (a) of this section and is overpacked as specified in § 177.841(e) of this subchapter or in an overpack which is a UN 1A2, 1B2, or 1N2 drum tested and marked for a Packing Group II or higher performance level.