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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 #21-0061

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

Interpretation Response Details

Response Publish Date:

Company Name: National Transportation Safety Board (NTSB)

Individual Name: Rachael Gunaratnam

Location State: DC Country: US

View the Interpretation Document

Response text:

August 31, 2021

Rachael Gunaratnam
Office of Railroad, Pipeline and Hazardous Materials Investigations
National Transportation Safety Board (NTSB)
490 L’Enfant Plaza
Washington, DC 20594

Reference No. 21-0061

Dear Ms. Gunaratnam:

This letter is in response to your June 1, 2021, email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to nurse tanks. Specifically, you seek clarification on whether the HMR require closure of a liquid discharge valve(s) on a nurse tank carrying anhydrous ammonia while in highway transportation.

The answer is yes. In accordance with the general requirements for packaging and packages in § 173.24(b), each package used for the shipment of hazardous materials under this subchapter shall be designed, constructed, maintained, filled, its contents so limited, and closed (emphasis added), so that under conditions normally incident to transportation, there will be no identifiable (without the use of instruments) release of hazardous materials to the environment Furthermore, in accordance with § 173.24(f), closures on packagings shall be so designed and closed that under conditions normally incident to transportation that there is no identifiable release of hazardous materials to the environment from the opening to which the closure is applied and the closure is leakproof and secured from loosening.

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

173.24(b), 173.24(f)

Regulation Sections

Section Subject
173.24 General requirements for packagings and packages