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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 #20-0044

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

Interpretation Response Details

Response Publish Date:

Company Name: Railsback Safety Professionals LLC

Individual Name: Rex Railsback

Location State: KS Country: US

View the Interpretation Document

Response text:

August 5, 2020

Rex Railsback
HazMat Specialist
Railsback Safety Professionals LLC
312 Lawrence Avenue
Lawrence, KS  66049

Reference No. 20-0044

Dear Mr. Railsback:

This letter is in response to your May 28, 2020, email and follow-up phone call requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to the classification of an engine containing a fuel with a flash point over 100 °F. Specifically, you reference a previous letter of interpretation issued by this office (Letter of Interpretation Ref. No. 20-0034), and request that PHMSA reconsider our position that an engine that contains a liquid fuel with a flash point of 125 °F should be classified and described as "UN3528, Engine, internal combustion, flammable liquid powered, 3" for transportation.

Additionally, you ask how a shipper should classify an internal combustion engine that contains fuel with a flash point of 142 °F. You correctly note that a liquid with a flash point of 142 °F is not a flammable liquid by definition in the HMR, i.e. a liquid with this flash point meets the definition of a combustible liquid (see § 173.120(b)). You suggest that the classification and description "UN3528, Engine, internal combustion, flammable liquid powered, 3" is incorrect for engines containing a flammable liquid fuel re-classed as a combustible liquid (e.g., flash point of 125 °F), and for engines with a fuel that meets only the definition of combustible liquid (e.g., flash point of 142 °F), because the proper shipping name (PSN) for UN3528 contains the words "flammable liquid."

The entry "UN3528, Engine, internal combustion, flammable liquid powered, 3" was added to the § 172.101 Hazardous Materials Table (HMT) in the HM-215N final rule (82 FR 15796, March 30, 2017). This entry replaced an existing entry for internal combustion engines, "UN3166, Engines, internal combustion, flammable liquid powered, 9." This amendment to the HMR was intended to align the HMR with international transportation requirements, and more clearly communicate the flammability hazard associated with the fuel inside the internal combustion engine. International regulations for the transportation of hazardous materials do not include a "combustible liquid" hazard classification. Therefore, the UN3528 entry added to the HMR by HM-215N only references "flammable liquid" as an additional description for the entry. However, use of UN3528 is not limited to only engines containing flammable liquids while excluding combustible liquids. Engines containing either flammable or combustible liquids are eligible for the exceptions provided for internal combustion engines in §§ 173.220 and 176.906.

The most appropriate HMT entry for an internal combustion engine powered by a flammable or combustible liquid is UN3528 even though the PSN includes the terms flammable liquid. In accordance with § 172.101(d)(4), shippers are instructed to modify the hazard class "3" to read "Combustible liquid" when that material is reclassified in accordance with § 173.150(e) or (f) of the HMR or has a flash point above 60 °C (140 °F) but below 93 °C (200 °F). However, § 172.101(d)(4) does not authorize modification of the PSN. Please note that because of the many exceptions provided to UN3528, internal combustion engines containing a flammable or combustible liquid are rarely subject to the HMR's shipping paper requirements. However, in the event that an internal combustion engine containing a combustible liquid is transported with an HMR-compliant shipping paper, the shipping description would read "UN3528, Engine, internal combustion, flammable liquid powered, Combustible liquid" instead of "UN3528, Engine, internal combustion, flammable liquid powered, 3." Additionally, please note that the HMR authorizes changes to the PSN with the approval of the Associate Administrator in accordance § 172.101(l)(2); therefore, a shipper may request a modification of the PSN for UN3528 to read "combustible liquid powered," if the shipper believes it is necessary.

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

172.101(l)(2), 172.101(d)(4), 173.120(b), 173.150(e) or (f) 173.220, 176.906

Regulation Sections

Section Subject
172.101 Purpose and use of hazardous materials table
173.120 Class 3-Definitions
173.150 Exceptions for Class 3 (flammable and combustible liquids)
173.220 Internal combustion engines, vehicles, machinery containing internal combustion engines, battery-powered equipment or machinery, fuel cell-powered equipment or machinery
176.906 Stowage of engines and machinery