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Interpretation Response #23-0105

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

Interpretation Response Details

Response Publish Date:

Company Name: SET Environmental, Inc.

Individual Name: David Olsen, Jr.

Location State: TX Country: US

View the Interpretation Document

Response text:

April 17, 2024

David Olsen, Jr.
Technical Compliance Manager
SET Environmental, Inc.
14020 Interdrive West
Houston, TX  77032

Reference No. 23-0105

Dear Mr. Olsen:

This letter is in response to your December 21, 2023, email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to self-reactive materials and associated concentration limitations in the § 173.224(b) Self-Reactive Materials Table. Specifically, you ask for clarification regarding the concentration limit for "UN3224, Self-reactive solid type C, 4.1 (N,N'-Dinitrosopentamethylenetetramine)" as denoted in column (3) of the table.

We have paraphrased and answered your questions as follows:

Q1. You state that the Self-Reactive Materials Table found in § 173.224 does not reference minimum concentrations using symbols similar to those used for maximum concentration entries. You ask whether a whole number without symbols in column 3—82% in the case of N,N'-Dinitrosopentamethylenetetramine—is to be viewed as a minimum concentration percentage.

A1. The answer is no. It is not the intention of the table for a whole number to be viewed as a minimum concentration percentage. Minimum concentration percentages are only listed as part of a range, and in the example, you cited, the 82% reflects the maximum concentration percentage allowed.

Q2. You note that you are aware of a shipper that transports the material in concentrations greater than 82%, specifically, 93.85%-94.04%. You ask whether the product is properly packaged for transport as a "UN3224" at this concentration.

A2. In accordance with § 173.22 of the HMR, it is the shipper's responsibility to properly classify and describe a hazardous material. However, based on the information provided, the product concentration exceeds the maximum specified concentration allowed for this material under § 173.224(b). Self-reactive materials not listed in the § 173.224(b) Self-Reactive Materials Table must be approved by the Associate Administrator prior to transport, in accordance with the procedure described in § 173.124(a)(2)(iii).

Q3. If the answer to question Q2 is no, you ask what the whole numbers with no associated symbols mean in this table.

A3. The whole numbers on the Self-Reactive Materials Table represent the maximum concentrations authorized.

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

173.22, 173.124(a)(2)(iii), 173.224, 173.224(b)

Regulation Sections

Section Subject
173.124 Class 4, Divisions 4.1, 4.2 and 4.3-Definitions
173.22 Shipper's responsibility
173.224 Packaging and control and emergency temperatures for self-reactive materials