Interpretation Response #24-0104

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

Interpretation Response Details

Response Publish Date: 03/27/2025

Company Name: AECOM Technical Services, Inc.

Individual Name: Ms. Carolyn Norris

Location State: NC Country: US

View the Interpretation Document

Response text:

March 27, 2025

Ms. Carolyn Norris
Project Manager
AECOM Technical Services, Inc.
5438 Wade Park Boulevard
Suite 200
Raleigh, NC  27607

Reference No. 24-0104

Dear Ms. Norris:

This letter is in response to your October 24, 2024, letter requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to classification of Division 4.2 self-heating substances. Specifically, is the alternative to the testing method described in the United Nations (UN) Manual of Tests & Criteria described in your letter have technical merit in this Office's opinion? According to your letter, the material to be tested exhibits the characteristic of a self-heating material; though, the exact test as described in the UN Manual of Tests & Criteria cannot be performed.

Yes. The method described in the UN Manual of Tests & Criteria, Test N.4 – test method for self-heating substances, requires testing of samples in 25 mm and 100 mm cubes at discrete temperatures to establish whether a material meets the definition of a Division 4.2 self-heating material and to determine the packing group. You state that your alternative method mimics the test set out in the UN Manual of Tests & Criteria for the Division 4.2 self-heating material except that—due to the form of the material—you did not use a 25 mm or 100 mm sample cube. You state that the test was performed as a thin layer on a substrate measuring 152.5 mm x 152.5 mm—the form it will be in when offered for transportation. You note that your testing demonstrated that in this form, the material exhibits self-heating behavior.

In accordance with § 173.22 of the HMR, it is the shipper's responsibility to classify properly a hazardous material. This Office generally does not perform this function. However, based on the test data as described in your letter, we agree with your determination that it is appropriate to class the material—when offered as a thin layer on a substrate measuring 152.5 mm x 152.5 mm—as a Division 4.2 self-heating material.

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

Sincerely,

T. Glenn Foster
Chief, Regulatory Review and Reinvention Branch
Standards and Rulemaking Division

173.22

Regulation Sections