# HMT Associates, L.L.C — Hazardous Materials Safety Interpretation **Citation:** 06-0180 **Type / status:** guidance / guidance **Agency:** Pipeline and Hazardous Materials Safety Administration **Effective:** Not stated **Published:** 2006-10-12 06-0180 response to HMT Associates, L.L.C concerning 173.115, 173.22. ## Document text <<>> S. Departmel f Transportatic 400 Seventh Street, S.W. Washington, D.C. 20590 Hazardous Materials Safety Pipeline and OCT 12 2006 Administration Mr. E.A. Altemos HMT Associates, L.L.C. Ref. No. 06-0180 603 King St., Suite 300 Alexandria, VA 22314-3105 Dear Mr. Altemos: description, and associated transportation requirements for materials under the Hazardous This is in response to your August 1, 2006 letter regarding the proper classification, Materials Regulations (HMR; 49 CFR Parts 171-180). Specifically, you state your product, solid carbon dioxide, contains an ozone concentration which is above the typical naturally-occurring concentrations and has been added to your product during the manufacturing process. You ask whether, because the ozone concentration in your material does not meet the definition of a Division 2.3 gas, the proper shipping name, "Carbon dioxide, solid or Dry ice" (UN 1845) is the proper classification and description of your material. hazardous material in accordance with Parts 172 and 173 of the HMR, and to determine Section 173.22 of the HMR requires a shipper to properly class and describe the that the packaging or container is an authorized packaging in accordance witi: Part 173. concentration does not meet the definition of any hazard class or division in the HMR, This Office does not perform that function. However, if you determine that the ozone including Division 2.3, and is not a hazardous substance or hazardous waste, "Carbon dioxide, solid or Dry ice" (UN 1845) would be the proper classification and description of your material. I hope this intormation is helpful. Sincerely, Tom s. Gale, Chief, Standards Development Office of Hazardous Materials Standards 173.22 060180 173.115 <<>> Foster 3173.22 § 173-115 HMT ASSOCIATES, I.I.c. Shipper's Responsehra Definition ALEXANDRIA, VA 22314-3105 06-0180 703-549-0727 FACSIMILE: 703-549-0728 WRITER'S DIRECT DIAL NUMBER (703) 549-0727, Ext. 11 August 1, 2006 Dr. Charles Ke Sciences Branch (PHH-21) Office of Hazardous Materials Technology Pipeline and Hazardous Materials Safety Administration Department of Transportation Washington, DC 20590-0001 Dear Dr. Ke: This is to request your confirmation of the proper classification, description, and associated transport requirements applicable under the Hazardous Materials Regulations ("the HMR", 49 CFR Parts 171-180) to solid carbon dioxide which contains a concentration of ozone that is above the typical naturally occurring concentration. The material concerned is solid carbon dioxide ("dry ice") which may be in pellet, block, or other solid form, and which contains a generally uniform distribution of ozone which has been added to the material during the manufacturing process. The approximate concentration of ozone in the material is 20 ppm (by weight). As you know, gaseous ozone would meet the criteria for classification in Division 2.3, and would exhibit other hazardous characteristics (i.e., strong oxidizing properties). However, owing to the relatively low concentration of the ozone in the material, the gas evolved as the material sublimes does not meet the criteria for classification in Division 2.3, does not exhibit the characteristics of an oxidizing gas for purposes of transport classification, and poses essentially the same hazard in transportation as does the carbon dioxide that is evolved by the sublimation of "normal" dry ice. Based on the foregoing, it is my conclusion that the dry ice/ozone mixture described above poses a hazard in transportation essentially no different from that of "normal" dry ice. Consequently, <<>> HMT ASSOCIATES, L.L.C. August 1, 2006 Dr. Charles Ke Page 2 Ibelieve this material can be properly described as "Carbon dioxide, solid or Dry ice" (UN 1845), classified in Class 9, and transported under the requirements and exceptions in the HMR as applicable to a material so described. Your confirmation of this conclusion is requested. Should you disagree with this conclusion, your guidance is requested as to the proper classification and description of the material for transportation. As offered for transportation, neither the material itself nor the gas evolved from it would meet the criteria for classification in any hazard class. With regard to Class 9, as you know there are no quantitative criteria for classification in this "miscellaneous" hazard class. While this material may nevertheless be considered a candidate for classification in Class 9 under the qualitative criteria in § 173.140(b) and description as an "Aviation regulated solid, n.o.s." (UN 3335), this is considered inappropriate for this material for two reasons. Firstly, unlike use of the "Dry ice" description, use of this proper shipping name would result in the material being considered regulated in air transportation but not for transportation by vessel. In addition, the packaging required for aviation regulated solids (§ 173.204) - unlike the packagings prescribed for dry ice (§ 173.217) - does not provide for the necessary release of the sublimed gas from the packaging in order to prevent rupture or failure of the packaging during transport. For these reasons, if this material is not classified in Class 9 and described as "Carbon dioxide, solid or Dry ice" (UN 1845), it is entirely unclear how it should be classified and described under the HMR in that there is no other available classification and description that will ensure application of the appropriate conditions, limitations, and packaging requirements on its transport. In closing, please do not hesitate to contact me if you have questions or need additional information concerning this matter. Thank you for your consideration of this request, and I look forward to your response at your earliest opportunity. Sincerely, cadet E. A. Altemos cc: Mr. Ed Mazzullo (PHH-10) ## Provenance - Official: Yes - Source: - Source ID: `phmsa` - SHA-256: `f3fa235a32f136fd08e157f830117e3165244180858e6f0baf33486c474c41df` - Retrieved: 2026-08-20T00:59:31.977Z - Exported: 2026-08-22T11:39:12.596Z - Document slug: `phmsa-interpretation-06-0180` ### Source metadata ```json { "materialSubtype": "interpretation", "interpretationArea": "hazardous_materials", "representation": "full_text_from_official_pdf", "companies": [ "HMT Associates, L.L.C" ], "individuals": [ "Mr. E.A. 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