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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 #15-0237 ([Slide Products, Inc.] [Mr. Michael Muth])

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

Interpretation Response Details

Response Publish Date:

Company Name: Slide Products, Inc.

Individual Name: Mr. Michael Muth

Location State: IL Country: US

View the Interpretation Document

Response text:

May 11, 2016

Mr. Michael Muth
Slide Products, Inc.
430 Wheeling Road
Wheeling, IL 60090

Reference No.: 15-0237

Dear Mr. Muth:

This letter is in response to your November 23, 2015 email and subsequent phone call requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to hot water bath testing requirements for aerosol cans.  Specifically, you ask what temperature and length of time is required to perform a hot water bath test in accordance with § 173.306 for Department of Transportation (DOT) 2Q canisters filled to either 90% or above 95% of the can’s fill volume.

As provided by § 173.306(a)(3)(v), each filled, metal aerosol container must be subjected to a test performed in a hot water bath.  The duration of the water bath will vary based on the temperature of the water bath and the properties of the contents of the canister.  If the liquid phase of the material does not exceed 95% of the capacity of the container at 50 °C, the temperature of the bath and the duration of the test must be such that the internal pressure reaches that which would be reached at 50 °C (122 °F).  If the contents exceed 95% capacity, the temperature and duration of the test must be such that the internal pressure of the canister reaches that which would be reached at 55 °C (131 °F).  The HMR does not specify a method for measuring the internal temperature of the canister.  

It should be noted that on January 21, 2016, PHMSA published a final rule in the Federal Register, titled "Hazardous Materials: Adoption of Special Permits (MAP–21) (RRR);" (Docket No. PHMSA–2013–0042 (HM–233F); [81 FR 3635]).  This final rule incorporated several longstanding special permits into the HMR, including those related to alternatives to the hot water bath test requirements for aerosols.  As of February 22, 2016, instead of subjecting the containers to a hot water bath, the following alternative tests are also authorized under
§ 173.306(a)(3)(v):

(A) Alternative water bath test.  This paragraph authorizes a combination of a hot water bath test, a weight test, and visual inspection.  Only one container out of each lot of 2,000 is subjected to the hot water bath test, a second is subjected to a weight test, the results of which must be compared to weight specification for the container as outlined in quality control procedures, and finally, the remainder of the lot must be visually inspected by examining the valve, crimp, and seam areas for evidence of leakage.
(B) Automated pressure test.  This paragraph authorizes the use of an automated process for pressure checks (i.e., an “automated in-line pressure check”).  This is a performance based test which requires the development of operating procedures inclusive of the basic components the procedures must address (e.g. inclusion of rejection criteria and periodic inspection).
(C) Weight test.  This paragraph authorizes the use of an automated process to check the weight of filled containers (i.e., an “automated in-line weight check”).  Comparison of the weight of a container against the pre-determined target weight for the container provides an indication of the proper filling of the container.
(D) Leakage test.  This paragraph authorizes the use of a high pressure air test on empty containers combined with a leakage test for filled containers.

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


T. Glenn Foster
Chief, Regulatory Review and Reinvention
Standards and Rulemaking Division
173.306(a)(3)(v), 173.306

Regulation Sections

Section Subject
173.306 Limited quantities of compressed gases
173.306 Limited quantities of compressed gases