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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 #11-0052 ([Honeywell Inc.] [Ms. Claire Matlon])

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

Interpretation Response Details

Response Publish Date:

Company Name: Honeywell Inc.

Individual Name: Ms. Claire Matlon

Location State: NJ Country: US

View the Interpretation Document

Response text:

April 19, 2011




Ms. Claire Matlon

Honeywell Inc.

101 Columbia Road

Morristown, NJ 07962

Reference No.: 11-0052

Dear Ms. Matlon:

This responds to your letter requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to the internal capacity limits for a specification Department of Transportation (DOT) 39 cylinder intended to contain a Division 2.1 liquefied compressed gas.

In your letter, you state that the material you plan to ship is a new molecule, used as a replacement refrigerant for Refrigerant gas R134a in the automotive air conditioning market. Your material has a boiling point greater than -50 °C, and a critical point above 65 °C. In accordance with § 173.115, your material is considered a low pressure Division 2.1 liquefied compressed gas, and you have classified your material as "UN 3161, Liquefied gas, flammable, n.o.s. (2,3,3,3-Tetrafluoroprop-1-ene)." You request confirmation of your conclusion that it is permissible to ship a Division 2.1 flammable gas in a DOT 39 specification cylinder with no restrictions on the internal volume.

In accordance with § 173.302a, for "a DOT 39 cylinder filled with a Division 2.1 material, the internal volume of the cylinder may not exceed 1.23 L (75 cubic inches)." This internal volume limitation only applies to Division 2.1 non-liquefied materials.

The filling requirements for liquefied compressed gases in DOT specification cylinders are based on the type of gas contained in the cylinder and are found in § 173.304a of the HMR. In addition, § 173.304a(a)(2) provides a table listing various types of liquefied gases and their corresponding maximum permitted filling densities. As you note in your incoming letter, the material you wish to ship is not specifically listed in the table in this section. For gases not specifically listed in the table in § 173.304a(a)(2), the filling density can be determined using the

formula provided in "Note 1" to that table. Therefore, the filling density for any cylinder containing your material, including a DOT specification 39, can be determined by calculating the percent ratio of the weight of the gas in the packaging to the weight of the water the container will hold at 16 oC (60 oF).

It should also be noted that cylinders built to meet a DOT 39 specification may not have a maximum water capacity that exceeds 55 pounds (1,526 cubic inches) for cylinders with service pressure of 500 p.s.i.g. or less, and 10 pounds (277 cubic inches) for cylinders with service pressure in excess of 500 p.s.i.g.

I hope this satisfies your inquiry. Please contact us if we can be of further assistance.


T. Glenn Foster

Chief, Regulatory Review and Reinvention Branch

Standards and Rulemaking Division

173.115, 173.302a, 173.304a

Regulation Sections

Section Subject
173.115 Class 2, Divisions 2.1, 2.2, and 2.3-Definitions
173.302a Additional requirements for shipment of nonliquefied (permanent) compressed gases in specification cylinders
173.304a Additional requirements for shipment of liquefied compressed gases in specification cylinders