USA Banner

Official US Government Icon

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure Site Icon

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Interpretation Response #02-0339 ([Occupational Safety and Health Administration] [Mike Marshall])

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

Interpretation Response Details

Response Publish Date:

Company Name: Occupational Safety and Health Administration

Individual Name: Mike Marshall

Location State: DC Country: US

View the Interpretation Document

Response text:


MAY 21, 2002

Subject: INFORMATION:: Response. to Request for Review

From: Delmer F. Billings, Chief
Standards Development, OHMS

To: Mike Marshall
Occupational Safety and Health Administration
Office of General Industry Compliance Assistance

This is iin reference to your facsimile dated February 7, 2002 and our telephone conversation, concerning the storage of Compressed Natural Gas (CNG) in DOT 3AA cylinders. Specifically, you asked if a cylinder made in conformance with a specification listed in the table in § 173.34(e)(13) and used exclusively in eNG service, instead of a periodic hydrostatic retest, be given a complete external visual inspection at the time periodic retest becomes due. In addition, you requested our office to review your draft of interpretation.

We suggest that the following language and/or corrections be used in your response:

Reply to Question number 1:

The Department of Labor's Occupational Safety and Health Administration (OSHA) workplace health and safety requirements apply to the storage of CNG in DOT 3 AA specification cylinders. In addition, your cylinders must conform to DOT regulatory requirements applicable to the maintenance and requalification of DOT 3M cylinders. The Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) apply to the transportation of hazardous materials in commerce, including packaging authorized for such transportation. Packaging manufactured in accordance with HMR requirements must be marked to indicate conformance with the specific requirements applicable to the packaging. The OSHA regulations incorporate the HMR by reference; thus, the OSHA standards also require DOT specification 3AA cylinders used for storage to be maintained and requalified in accordance with the HMR requirements. Further, cylinders used to transport hazardous materials in commerce are subject to HMR and may not be offered or transported unless they are maintained and requalified in accordance with the HMR.

OSHA/DOT Requirements:

As your facsimile notes, the visual inspection requirements in §173.34(eXIO) of the HMR are for cylinders used exclusively for materials specifically listed. However, the provision allowing performance of a visual inspection instead of a hydrostatic test applies only to cylinders used exclusively for the materials specifically listed in the table is contained in §173.34(eXI3). The material, CNG you
identified is not listed in the table. Therefore, cylinders used exclusively for CNG service does not qualify for the five-year complete external visual inspection in §173.34(e)(13). Thus, the hydrostatic test as specified in the§173.34(e) table must be used.

With regard to your reference to the Compressed Gas Association (CGA) pamphlets, C-6 and C-g, Section 173.34(e)(3) of the HMR prescribes that a DOT specification cylinder must be visually inspected, internally and externally, in accordance with CGA Pamphlets C-6, C6.1, C 6.2, as applicable. CGA pamphlet e-g applies to requalification of3HT specification cylinders thus would not be applicable to DOT 3M specification cylinders, as noted in your letter. In addition, the CGA pamphlets are specifically listed in the § 171.7 table which sets forth materials (e.g. CGA pamphlets) incorporated by reference into the HMR. Therefore, as prescribed under 173.34(cX2XvXC), the pamphlet maintained must be the edition incorporated by reference in § 171.7.

I hope this information is helpful. If you have further questions, please do not hesitate to contact this office


Regulation Sections

Section Subject
171.7 Reference material