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Interpretation Response #08-0178 ([ExxonMobil Chemical Company] [Mr. Ronald J. Stokes])

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

Interpretation Response Details

Response Publish Date:

Company Name: ExxonMobil Chemical Company

Individual Name: Mr. Ronald J. Stokes

Location State: NJ Country: US

View the Interpretation Document

Response text:

October 3, 2008




Mr. Ronald J. Stokes

ExxonMobil Chemical Company

Intermediates, Synthetics Product Stewardship

P.O. Box 3140

Edison, New Jersey 08818

Ref. No. 08-0178

Dear Mr. Stokes:

This responds to your June 25, 2008 letter requesting clarification of the classification and training requirements in the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) for rail shipments. Specifically, you ask whether the HMR apply to the transportation of materials that release hydrogen into the vapor space of a tank car.

According to your letter, you ship various products by rail tank car. Some of these products meet the HMR definition for combustible liquid; others do not meet the definition for any hazard class. In all cases, however, these products release unincorporated hydrogen into the vapor space of the tank car. The vapor pressure is less than 40 psi; however, the hydrogen has been measured at between 2% and 80% concentration. The published flammable limits (LEL-UEL) of hydrogen are 4% and 75%. You ask how these materials should be classed and transported.

Under the HMR, hydrogen is classed as a flammable gas irrespective of the pressure it exerts in its packaging. A material that releases a hazardous amount of hydrogen into the vapor space of its packaging during transportation must be classed and transported to address the hazard posed by the hydrogen unless the material is stabilized or inhibited to preclude such a release. For example, the release of hydrogen during transportation could be inhibited through the use of a nitrogen blanket, provided the vapor pressure of the nitrogen does not exceed 40 psi. If the materials you ship are stabilized or inhibited to preclude the release of hydrogen, they may be transported as unregulated materials or as combustible liquids, as appropriate.

Alternatively, a material that does not meet the definition of any of the hazard classes defined in Part 173 of the HMR, but that releases hydrogen into the vapor space of its container or packaging under the conditions described in your letter may be described as "UN 1049, Hydrogen, compressed, 2.1" and transported in accordance with all applicable requirements, including appropriate packaging and hazard communication. A material that meets the definition for a combustible liquid and releases hydrogen into the vapor space of its container or packaging under the conditions described in your letter may be described as "UN 1954, Compressed gas, flammable, n.o.s., 2.1 ( hydrogen, compressed; combustible liquid)" and transported in accordance with all applicable requirements, including appropriate packaging and hazard communication.

You also ask whether a person who loads or unloads non-hazardous materials to or from a bulk packaging must be trained in accordance with Subpart H of Part 172. The answer is no. The training requirements in the HMR do not apply to persons who handle unregulated materials. However, persons who load and/or unload hazardous materials as described in this letter must be trained.

I hope this answers your inquiry.

Sincerely,

Susan Gorsky

Acting Chief, Standards Development

Office of Hazardous Materials Standards

172.704, 172.101

Regulation Sections

Section Subject
172.101 Purpose and use of hazardous materials table
172.704 Training requirements