Cylinders Containing Division 2.3 Gases
Pipeline and Hazardous Materials Safety Administration · Jun 27, 1997 · Reference No. 97-0168
Reggie’s quick take
A company asked how the valve and overpack rules apply to DOT 3E1800 cylinders holding poison gases in Division 2.3. PHMSA said a cylinder with no fitted valve protection must go in an overpack made of wood, plastic, or fiberboard, such as a 4C1, 4G, or 4H2 box, under § 173.40(d)(1). That overpack must also meet § 173.25, and it satisfies the outside packaging rule in § 173.301(k). Either way, valve protection must keep the valve from deforming or breaking in a 2.0 m drop. PHMSA said the UN box codes only name box types and do not require UN performance testing, and it plans to clarify that in a later rulemaking.
Written by AI (Claude) on Oct 22, 2026. Robots make mistakes and leave things out, so the letter below is what counts. Not legal advice.
This is in response to your March 25, 1997 letter concerning requirements of 49 171.40(d) setting out additional protection requirements for thin-walled cylinders and for cylinders equipped with valves, specifically with regard to DOT Specification 3E1800 cylinders containing Division 2.3 gases.
Under 49 CFR 173.301(k), a DOT 3E cylinder is required to be shipped in a strong outside packaging which provides protection for the cylinder and, unless the cylinder has a protective collar or neck ring, protection to the valve against accidental functioning and damage. For poisonous materials required to be packaged in cylinders, 49 CFR 173.40 specifies additional requirements.
Under § 173.40(d), a cylinder must either (1) be overpacked in a wooden, plastic or fiberboard box or (2) be equipped with a protective cap or other means of valve protection. Under either paragraphs (d)(1) or (d)(2), valve protection must be sufficient to prevent deformation and breakage resulting from a 2.0 m drop. Section 173.40(d)(1) States that a "cylinder which does not have fitted valve protection must be overpacked in a 4C1, 40, 4F, 4G, 4H or 4H2 box." RSPA did not intend to require that the overpacks meet UN performance standards (i.e., the overpacks need not be manufactured, tested and marked in conformance with subparts L and M of 49 CFR Part 178). We listed the UN designations to refer to the types of boxes to be used (i.e., wood, fiberboard or plastic), rather than to specify a UN standard. We will change this provision in a future rulemaking action to clarify that overpacks are not required to meet UN performance standards.
For cylinders which do not have fitted valve protection and are overpacked, the overpack must conform to the provisions of 49 CFR 173.25. An overpack that satisfies the requirements of § 173-40(d)(1) also satisfies the requirements of § 173.301(k).
Under § 173.40(d)(2), cylinders that are not overpacked in a box in accordance with paragraph (d)(1) must be equipped with a protective cap or other means of valve protection. Because paragraph (d)(2) applies to situations where the cylinders are not overpacked in boxes in accordance with (d)(1) (i.e., wooden, plastic or fiberboard boxes that are capable of preventing deformation and breakage from a drop of 2.0 m), the "other means" of valve protection would not be strong outside packaging already required by 173.301(k) and 173.40(d)(1).
A letter of interpretation applies the regulations to the facts the requester described. It isn’t a regulation and isn’t legal advice. The agency’s copy.