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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 #22-0028

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

Interpretation Response Details

Response Publish Date:

Company Name: DOT Training Solutions

Individual Name: Mr. Randy Decker

Location State: KS Country: US

View the Interpretation Document

Response text:

January 24, 2023

Mr. Randy Decker
Safety Consultant
DOT Training Solutions
P.O. Box 25311
Overland Park, KS 66225

Reference No. 22-0028

Dear Mr. Decker:

This letter is in response to your March 17, 2022, email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to the testing and inspection requirements for multi-compartment Department of Transportation (DOT) specification cargo tanks. In your email, you state that §§ 180.407(g)(1)(vi) and 180.407(h)(1) of the HMR require that each cargo tank of a multi-tank cargo tank motor vehicle be pressure-tested and leakage-tested respectively, with the adjacent cargo tanks empty and at atmospheric pressure. Furthermore, you ask whether a void at atmospheric pressure between double bulkheads—as described in your email—may be considered an adjacent compartment for the purposes of pressure and leakage testing under § 180.407.

The answer is no. Sections 180.407(g)(1)(vi) and (h)(1) both state that "each cargo tank of a multi-tank cargo tank motor vehicle must be tested with the adjacent cargo tanks empty and at atmospheric pressure." Under § 178.345-1(c), the HMR define a "void" as "the space between tank heads or bulkheads and a connecting structure." Therefore, a "void" does not meet the definition of a cargo tank.

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

178.345-1(c), 180.407, 180.407(g)(1)(vi), 180.407(h)(1)

Regulation Sections

Section Subject
178.345 General design and construction requirements applicable to Specification DOT 406 (178.346), DOT 407 (178.347), and DOT 412 (178.348) cargo tank motor vehicles
180.407 Requirements for test and inspection of specification cargo tanks