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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 #25-0045

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

Interpretation Response Details

Response Publish Date:

Company Name: MP Environmental Services, Inc.

Individual Name: Mike Reed

Location State: CA Country: US

View the Interpretation Document

Response text:

March 27, 2026

Mike Reed
MP Environmental Services, Inc.
3400 Manor Street
Bakersfield, CA  93308

Reference No. 25-0045

Dear Mr. Reed:

This letter is in response to your April 11, 2025 email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to cargo tank certification plates in reserved § 178.340-10.

We have paraphrased and answered your questions as follows:

Q1. Is it permissible under § 178.340-10 to leave the loading limits section empty or listed as "none" on the cargo tank certification plate?

A1. No. Section 178.340-10(b)(1) requires loading limits be listed on the cargo tank certification plate. Determining the loading limits is part of certification required in 178.340-10(b).

Q2. Is it permissible under § 178.340-10(b)(1) to provide the loading limit requirements in inches of mercury (inHg) instead of gallons per minute (gpm) or pounds per square inch gauge (psig)?

A2. No. The requirements in § 178.340-10(b)(1) specify that the loading limit be expressed in gpm, psig, or both. It is the opinion of this Office that listing the pressure in inches of mercury (Hg) does not meet the intent of § 178.340-10(b)(1).

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

Sincerely,

Alexander Wolcott
Acting Chief, Regulatory Review and Reinvention Branch
Standards and Rulemaking Division

178.340-10(b)

Regulation Sections