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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Interpretation Response #25-0043

Below is the interpretation response detail and a list of regulations sections applicable to this response.

Interpretation Response Details

Response Publish Date:

Company Name: Betts Industries, Inc.

Individual Name: David J. Adams

Location State: PA Country: US

View the Interpretation Document

Response text:

July 2, 2025

David J. Adams
Director of Design Engineering
Betts Industries, Inc.
1800 Pennsylvania Ave. West 
Warren, PA  16365

Reference No. 25-0043

Dear Mr. Adams:

This letter is in response to your April 10, 2025 email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to a cargo tank motor vehicle (CTMV). Specifically, you ask about the use of an engineered copolymer as the material of construction for certain parts of a CTMV.

We have paraphrased and answered your questions as follows:

Q1. Does the requirement for the use of nonmetallic materials outlined in § 178.345-9(h) apply to the body of a pressure relief device (PRD), such as a normal vent used on a Department of Transportation (DOT) 406 CTMV?

A1. No. Section § 178.345-9(h) is applicable for components outboard of the lading retention system and does not apply to PRDs. PRD requirements are generally outlined in § 178.345-10 for DOT 400 series CTMVs, and further specified in §§ 178.346-3, 178.347-4, and 178.348-4 for DOT 406, DOT 407, and DOT 412 CTMVs, respectively.

Q2. Does the HMR prohibit the use of a high-performance engineered copolymer as the material of construction for the body of a normal vent on a DOT 406 CTMV?

A2. No. The HMR do not specify requirements or restrictions pertaining to materials of construction for PRDs on DOT 406 CTMVs; however, the pressure relief system—including normal vents—must meet the performance requirements in §§ 178.345 and 178.346, as well as the general packaging compatibility requirement in § 173.24 regarding the use of a packaging and its lading.

I hope this information is helpful. Please contact us if we can be of further assistance.

Sincerely,

Dirk Der Kinderen
Chief, Standards Development Branch
Standards and Rulemaking Division

§ 173.24, § 178.345, § 178.345-9(h), § 178.345-10, § 178.346, § 178.346-3, § 178.347-4, § 178.348-4

Regulation Sections