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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 #23-0033

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

Interpretation Response Details

Response Publish Date:

Company Name: Sensors, Inc.

Individual Name: Mr. Doug Heisler

Location State: MI Country: US

View the Interpretation Document

Response text:

May 8, 2023

Mr. Doug Heisler
Manager, Quality and Service
Sensors, Inc.
6812 State Rd.
Saline, MI  48176

Reference No. 23-0033

Dear Mr. Heisler:

This letter is in response to your March 27, 2023, email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) regarding the applicability of the HMR to a Portable Emission Measurement System, which contains DOT specification cylinders that release a controlled amount of certain Division 2.1 and 2.2 materials without removing the cylinders from the vehicle on which they are transported. Specifically, you state that you install these systems on your customers' vehicles a few times per year to record emissions measurements and that these systems utilize a fuel bottle during this measurement while your customers operate their vehicle. You further state that your company currently possesses a Special Permit (Ref. No. 15839) that authorizes the transportation of these systems and the controlled release of certain Division 2.1 and 2.2 materials. You ask whether this activity is subject to the HMR and therefore, whether you need to renew your special permit.

Based on the information you have provided, the answer is no. Section 171.1(b) and (c) state that the requirements of the HMR apply to each person who offers a hazardous material for transportation in commerce or transports a hazardous material in commerce. It is the opinion of this Office that auxiliary equipment attached to a motor vehicle with the intent of measuring vehicle emissions is not considered to be "in commerce." Therefore, the requirements of the HMR are not applicable to your device.

However, please be aware that there may be applicable requirements from other Federal agencies such as the Federal Motor Carrier Safety Administration (FMCSA), who can be reached at 1-800-832-5660, the National Highway Traffic Safety Administration (NHTSA), who can be reached at 1-888-327-4236, and the Environmental Protection Agency (EPA), who can be reached at 1-734-214-4333.

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


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

171.1(b) and (c)

Regulation Sections

Section Subject
171.1 Applicability of Hazardous Materials Regulations (HMR) to persons and functions