# Space Gateway Support, LLC — Hazardous Materials Safety Interpretation **Citation:** 05-0053 **Type / status:** guidance / guidance **Agency:** Pipeline and Hazardous Materials Safety Administration **Effective:** Not stated **Published:** 2005-05-12 05-0053 response to Space Gateway Support, LLC concerning 171.1, 173.22. ## Document text <<>> U.S. Department of Transportation 400 Seventh Street, S.W. Washington, D.C. 20590 Pipeline and MAY 12 2005 Hazardous Materials Safety Administration Mr. William Deneuté Ref No.: 05-0053 P.O. Box 21237 Space Gateway Support, LLC Kennedy Space Center, FL 32815 Dear Mr. Deneuté: This responds to your February 23, 2005 letter requesting clarification of the weight percent threshold for classification of mixtures of nitric oxide and dinitrogen tetroxide under the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180). You state that a threshold of 11% nitric oxide in a mixture with dinitrogen tetroxide appears to be the poin: where the characteristics of the mixture diverge from that of pure "Dinitrogen tetroxide, UN1067." You request that 11% be the threshold level where a mixture of nitric oxide and dinitrogen tetroxide is classified as "Nitric oxide and dinitrogen tetroxide mixtures, UN1975" rather than "Dinitrogen tetroxide, UN1067." In accordance with § 173.22, it is the shipper's responsibility to determine the shipping description for the material being transported. When selecting a proper shipping name, the shipper must select the name that most appropriately describes the material (see § 173.101(c)(12)). For a mixture of nitric oxide and dinitrogen tetroxide that meets the definition of a Division 2.3 material that is poisonous by inhalation in Hazard Zone A and exhibits oxidizer and corrosive subsidiary hazards, it is the opinion of this Office that, notwithstanding the percentage of nitric oxide in the mixture, the most appropriate shipping description is "Nitric oxide and dinitrogen tetroxide mixtures, 2.3 (5.1, 8), UN 1975." The proper shipping name "Dinitrogen tetroxide" may be used only for pure dinitrogen tetroxide that meets the definition of a Division 2.3 material that is poisonous by inhalation in Hazard Zone A and exhibits oxidizer and corrosive subsidiary hazards. I hope this information is helpful. Please contact us if you require additional assistance. Sincerely, / Chief, Standards Development Office of Hazardous Materials Standards 14/.1 050053 173.22 <<>> Supko 3171:1 - Space Gateway Support, LLC Exemption Kennedy Space Center, FL 32815-0237 P.O. Box 21237 05-0053 DATE: February 23, 2005 230-05-036 TO: Edward T. Mazullo. Director Office of Hazardous Materials Standards US DOT / RSPA (DHM-10) 400 7" Street SW. Washginton, D.C. 20590-0001 SUBJECT: REQUEST FOR WRITTEN INTERPRETATION REGARDING THE WEIGHT PERCENT THRESHOLD FOR CLASSIFYING NITRIC OXIDE AND DINITROGEN TETROXIDE MIXTURES WITH THE UN1975 IDENTIFIER - 49 CFR 172-101. Dear Mr. Mazullo, Currently, NASA - KSC transports MON-1 and MON-3 (Mixed Oxides of Nitrogen and Dinitrogen Tetroxide) under exemptions DOT-E 10887 and 11383 (as grantee) under the UN ID 1067 (DiNitrogen Tetroxide.) NASA is also a party to exemptions DOT-E 03121 and 11580 and will forward this interpretation to the grantees (DOD and Columbiana Boilers.) Our concerr. is that the weight percent of NO is so low (1% and 3% respectively) that the mixtures ex nibit the same characteristics as the pure Dinitrogen Tetroxide. There are occasions where MON-10 is transported under some of the above exemptions also. This mixture does exhibit a higher vapor pressure so the UN 1975 designation may be prudent there but we believe the vapor pressure really diverges above 11% NO by weight. If there is no set weight percent which the OHM has identified, we would like to submit 11% (MON-11) as a threshold level as that is the point where the characteristics appear to diverge from NTO. We would concede that a conservative level would be 7% NO by weight which is the point where the vapor pressures shows a 50% increase above atmospheric pressure. Currently there is a modification request in by NASA for adding UN 1975 to DOT-E 11383 as an additional Division 2.3 material in non-DOT specification Steel cylinders (FR Vol. 70, No. 13, 1/21/05 - 11383-M.) If the conservative weight percent of NO (7%) is accepted as a limit for UN 1975, we would respectfully request the modification be cancelled as MON-10 is not transported under that exemption. Sincerely, wallan C lenenti, 2/23/05 William Derieuté Space Gateway Support, LLC Attachments Vapor Pressure Calculations & interpolation chart Co: Chuck Davis, TA-E3; Kyrn Craig, UPC-272 Dwayne Breaux, SGS-127; Hemant Solanky, SGS-127 * Recycled paper ## Provenance - Official: Yes - Source: - Source ID: `phmsa` - SHA-256: `96a2014d2421b030ab78c189e28885c1e1db328881d43c0623689d5b7b85c6b3` - Retrieved: 2026-08-20T00:59:31.977Z - Exported: 2026-08-22T09:22:28.070Z - Document slug: `phmsa-interpretation-05-0053` ### Source metadata ```json { "materialSubtype": "interpretation", "interpretationArea": "hazardous_materials", "representation": "full_text_from_official_pdf", "companies": [ "Space Gateway Support, LLC" ], "individuals": [ "Mr. William Deneuté" ], "refIds": [ "05-0053" ], "catalogDates": [ "2005-05-12" ], "catalogParts": [ 171, 173 ], "catalogRowCount": 2, "sourceRecordUrls": [ "https://www.phmsa.dot.gov/node/52236" ], "linkedAttachmentUrls": [], "unavailableResponseUrls": [], "duplicateRepresentationUrls": [], "citedSections": [ "171.1", "173.22", "173.101(c)(12)" ], "catalogPageUrls": [ "https://www.phmsa.dot.gov/regulations/title49/section/1711", "https://www.phmsa.dot.gov/regulations/title49/section/17322" ], "pdfUrls": [ "https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretation%20Files/2005/050053.pdf" ], "representations": [ { "viewUrl": "https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretation%20Files/2005/050053.pdf", "detailUrl": null, "detailHtmlPath": null, "pdfUrl": "https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretation%20Files/2005/050053.pdf", "pdfArtifactPath": "data/sources/phmsa-interpretations/05-0053-b74c020835.pdf", "pdfArtifactSha256": "79079a2fb829e0906d2adfdd087f71dd3fe57e796fa12348229c310ded77cad5", "extractedTextPath": "data/sources/phmsa-interpretations/05-0053-b74c020835.v2.txt", "extractedTextSha256": "82fc30d28868724cc1ec5cc916b45938c557400c5d749f223e0276ee4ecf2f76", "pageCount": 2, "extractionVersion": 2 } ], "caveat": "Interpretations apply regulations to the facts presented and do not create independently enforceable requirements.", "jurisdiction": "US" } ```