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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 #18-0024

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

Interpretation Response Details

Response Publish Date:

Company Name: Versum Materials

Individual Name: Richard Schuyler

Location State: PA Country: US

View the Interpretation Document

Response text:

September 18, 2018

Richard Schuyler
Sr. Principal Mechanical Engineer
Versum Materials
357 Marian Avenue
Tamaqua, PA  18252

Reference No. 18-0024

Dear Mr. Schuyler:

This letter is in response to your February 21, 2018, email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to pressure relief devices (PRDs) for Multi-Element Gas Cylinders (MEGCs).  Specifically, you seek confirmation of your understanding that MEGCs transporting “UN2451, Nitrogen trifluoride” do not require PRDs in accordance with the Compressed Gas Association (CGA) S-1.1 pamphlet, which is incorporated by reference in § 171.7 of the HMR.

Your understanding is correct.  In accordance with § 173.301(f), a cylinder filled with a gas and offered for transportation must be equipped with one or more PRDs sized and selected as to type, location, quantity, and tested in accordance with CGA S-1.1.  When a person refers to CGA S-1.1, Table 3, the “T” code for nitrogen trifluoride indicates only specific PRDs are authorized for optional use during transportation thus, the CG-4 or CG-5 device must be used when a PRD is permissively selected.  Please note, when an optional PRD is selected, a person must comply with the requirements in §§ 173.301(f) and 178.75(f) for MEGCs installed with a PRD when applicable.

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


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

171.7, 173.301(f), 178.75(f)

Regulation Sections

Section Subject
171.7 Reference material
173.301 General requirements for shipment of compressed gases and other hazardous materials in cylinders, UN pressure receptacles and spherical pressure vessels
178.75 Specifications for MEGCs