Standards for steel, aluminum or other metal boxes.

(a)The following are identification codes for steel, aluminum, or other metal boxes:#

(1)4A for a steel box;#

(2)4B for an aluminum box; and#

(3)4N for an other metal box.#

(b)Construction requirements for steel, aluminum or other metal boxes are as follows:#

(1)The strength of the metal and the construction of the box must be appropriate to the capacity and intended use of the box.#

(2)Boxes must be lined with fiberboard or felt packing pieces or must have an inner liner or coating of suitable material in accordance with subpart C of part 173 of this subchapter. If a double seamed metal liner is used, steps must be taken to prevent the ingress of materials, particularly explosives, into the recesses of the seams.#

(3)Closures may be of any suitable type, and must remain secure under normal conditions of transport.#

(4)Maximum net mass: 400 kg (882 pounds).#