Interpretation Response #26-0048
Below is the interpretation response detail and a list of regulations sections applicable to this response.
Interpretation Response Details
Response Publish Date:
Company Name: Williams International
Individual Name: Kailee Tubbs
Location State: MI Country: US
View the Interpretation Document
Response text:
September 30, 2026
Kailee Tubbs
Williams International
2000 Centerpoint Parkway
Pontiac, MI 48341
Reference No. 26-0048
Dear Ms. Tubbs:
This letter is in response to your April 10, 2026 letter requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to the classification of an engine. You note that the engine assembly includes an igniter classified as "UN0325, Igniter, 1.4G," which is both an integral component of the engine and required for the operation of the engine. Specifically, you ask if the basic description "UN3166, Engine, internal combustion, flammable liquid powered, 9" is an appropriate classification and ask for confirmation that the engine with installed igniter would be eligible for the provisions of § 173.220(f)(1).
No. Following recent regulatory updates1, the Proper Shipping Name (PSN) associated with UN3166 has been amended to "Vehicle, flammable gas powered" or "Vehicle, flammable liquid powered." Therefore, UN3166 is no longer appropriate for your engine assembly. However, it is still correct that under § 173.56(i) the Associate Administrator (AA) for the Office of Hazardous Materials Safety may specify a classification or except an explosive material from the requirements of the HMR. In a previously issued letter of interpretation the AA determined that your 1.4G igniter is an integral part of the combustion engine and does not pose a hazard requiring an approval and may be excepted if the requirements of § 173.220(f)(1) are met2.
1 82 FR 15796 (March 30, 2017)
2 Williams International, Letter of Interpretation Reference Number 17-0039, available at: https://www.phmsa.dot.gov/regulations/title49/interp/17-0039
Under § 173.22, it is the shipper's responsibility to classify a hazardous material properly, in accordance with classification criteria provided in the HMR, prior to offering it for transportation to—or within—the United States. This Office does not normally perform this function. However, provided the 1.4G igniter is still an integral component of the engine and necessary for the operation of the engine in accordance with § 173.220(f)(1), a different entry, such as "UN3530, Engine, internal combustion, 9" may be more appropriate.
I hope this information is helpful. Please contact us if we can be of further assistance.
Sincerely,
Alexander Wolcott
Acting Chief, Regulatory Review & Reinvention
Standards and Rulemaking Division
173.22 173.56(i) 173.220(f)(1)