Venting Requirements for DOT Specification Tanks
Pipeline and Hazardous Materials Safety Administration · Apr 20, 1998 · Reference No. 98-0571
Interprets: 49 CFR § 178.345
Reggie’s quick take
A company asked whether DOT 407 or DOT 412 cargo tanks must use pressure relief devices stamped "U" by the American Society of Mechanical Engineers (ASME). PHMSA said no. The pressure relief requirements in § 178.345-10 are the ones that apply, and they do not stop a tank from using ASME-certified devices. PHMSA also said § 178.345-10 does not require an ASME "U" stamped device in addition to the devices the HMR already specifies.
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 letter requesting clarification of the venting requirements for DOT 407 and DOT 412 tanks under the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180). Your questions are paraphased and answered below:
Q1. Does the HMR require American Society Mechanical Engineers (ASME) "U" stamped
pressure relief devices on DOT 407 or DOT 412 cargo tank motor vehicles?
A1. The answer is no. The intent of the HMR is not to require ASME "U" stamped pressure relief devices on DOT 407 or DOT 412 cargo tanks. The provisions specified in § 178.345-10 are the applicable requirements for pressure relief devices used on a DOT 407 or DOT 412 cargo tank. These provisions do not preclude use of pressure relief devices certified to the ASME.
Q2. Does the HMR require an ASME pressure relief device in addition to the devices specified in 178.345-10?
A2. The answer is no. Section 178.345-10 does not require the use of an ASME "U" stamped pressure relief device in addition to the devices specified in the HMR.
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.