{"operation":"document","citation":"26-0022","title":"Air Liquide Advanced Materials — Hazardous Materials Safety Interpretation","source_type":"guidance","agency":"Pipeline and Hazardous Materials Safety Administration","status":"guidance","official":true,"published_on":"2026-08-13","effective_on":null,"summary":"26-0022 response to Air Liquide Advanced Materials concerning 172.202, 172.402, 173.22, 173.2a.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-interpretation-26-0022.json","markdown":"https://regulus.evalyn.ai/document/phmsa-interpretation-26-0022.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-interpretation-26-0022","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/2026-08/260022.pdf","body":"<<<PAGE 1>>>\n\n26-0022\nLarson\nj\n*\nI -*¯\n.-\nBranchburg, January 24th, 2026\nU.S. Department of Transportation\nStandards & Rulemaking Division- East Building\nPipeline Hazardous Materials Safety Administration\nAttn: Shane Kelley (PHH-10)\nDirector, Standards and Rulemaking Division\n1200 New Jersey Avenue, SE East Building, 2nd Floor\nWashington, DC 20590\nCertified Return-Receipt\nSubject: Request for formal Letter of Interpretation regarding Classification for a specific\nsilylamine compound, as it presents hazards similar to those of Trisilylamine.\nDear Mr. Kelley,\nThis letter is submitted to respectfully request a formal letter of guidance and interpretation from\nyour office regarding the classification of a specific silylamine compound. This material is\nprocessed by Air Liquide Advanced Materials; however, due to confidentiality concerns, we are\nunfortunately unable to disclose the chemical identity at this time.\nThis silylamine compound is a chemical substance developed for applications in the\nsemiconductor industry. It is an equivalent compound to Trisilylamine (CAS#13862-16-3) and\nexhibits similar characteristics as defined by the classification criteria outlined in 49 CFR\nSubpart D of Part 173:\n¯ Hazard Class Division 6.1: Toxic by Inhalation (Inhalation Hazard Zone B), PG I\n¯ Hazard Class Division 4.3: Water Reactive, PG I\no Hazard Class 8: Corrosive (Dermal), PG I\n¯ Hazard Class 3: Flammable Liquid, PG II\nBased on 49 CFR §173.2a, Precedence of Hazard Table, and available and appropriate D.O.T.\nBasic Descriptions found in 49 CFR §172.101 (Hazardous Materials Table), Air Liquide\nAdvanced Materials has selected the following description:\n\n<<<PAGE 2>>>\n\n@Air Liquide\n· Air Liquide Advanced Materials (ALAM)\n, 3040 US Highway 22\nBranchburg f:iew Jersey 08876\nUnited States of America\nUN3491, Toxic by inhalation liquid, water-reactive, flammable n.o.s. (Silylamine\ncompound)\nFor identifying this chemical for shipments offered throughout the United States and the\ninternational community, correspondence with professional and technical leaders within our\nindustry concurs with this decision.\nHowever, this description excludes the corrosive characteristics of this chemical.\nA similar request was submitted by Air Liquide regarding Trisilylamine (guidance letter reference\nNo. 13-0003, March 08, 2013). For transportation within the United States in accordance with\nthe HMR, § 172.402(a)(2) mandates that all hazardous materials with a Class 8, PG I,\nsubsidiary hazard must be labeled with a subsidiary CORROSIVE hazard warning label for all\nmodes of transport. This supplementary label presented significant difficulties when shipping\ntrisilylamine internationally, as shippers, freight forwarders/carriers, and non-U.S. customs\nofficials rely solely on the UN code hazards and require the removal of the \"CORROSIVE\" label\nprior to vessel loading.\nAir Liquide Advanced Materials and its partners are seeking regulatory guidance and\ninterpretation from your office on the proper classification of this silylamine compound based on\nthe current regulations of Title 49 CFR, specifically addressing how to properly account for the\ncorrosivity (Class 8) alongside the Toxic, Water\"'Reactive, and Flammable hazards.\nAir Liquide Advanced Materials is committed to the safe and compliant transportation of\nhazardous materials. Should you have any questions or require further information, please do\nnot hesitate to contact me directly at 908-465-2673 or by email at\nguillaume.husson@airliquide.com.\nRespectfully;\n- Guillaume, Husson\nGlobal Product Stewardship ·Manager\nAir Liquid� Advanced Mafe�ials\n\"·guil!aumeJ:iusson@airliquide.com\nMobile: +l 908 465 2673\n\n<<<PAGE 3>>>\n\n1200 New Jersey Avenue, SE\nWashington, DC 20590\nU.S. Department\nof Transportation\nPipeline and Hazardous\nMaterials Safety\nAdministration\nAugust 13, 2026\nGuillaume Husson\nGlobal Product Stewardship Manager\nAir Liquide Advanced Materials\n3040 US Highway 22\nBranchburg, NJ 08876\nReference No. 26-0022\nDear Mr. Husson:\nThis letter is in response to your January 24, 2026 letter requesting clarification of the Hazardous\nMaterials Regulations (HMR; 49 CFR Parts 171-180) applicable to the classification of a\nsilylamine compound. Specifically, you are seeking clarification on the classification of the\nchemical compound which exhibits the following hazards: Division 6.1, inhalation Hazard Zone\nB, Packing Group (PG) I; Division 4.3, PG I; Class 8, PG I; and Class 3, PG II. You state that,\nbased on the precedence of hazards described in § 173.2a, your company has selected the\ndescription “UN3491, Toxic by inhalation liquid, water-reactive, flammable, n.o.s. (Silylamine\ncompound), 6.1(4.3, 3), PG I.” You further state that this description excludes the corrosive\ncharacteristics of the material, and that § 172.402(a)(2), as referenced in a previous letter of\ninterpretation (LOI Ref No. 13-0003), mandates all materials with a Class 8, PG I subsidiary\nhazard be labelled with a CORROSIVE label.1 Lastly, you state that applying the CORROSIVE\nsubsidiary hazard label when the corrosive hazard is not identified in the shipping description for\nUN3491 has led to frustration of your shipments because many freight forwarders and carriers\nrely solely on the hazard codes in the description, and they require the removal of the\nCORROSIVE label.\nIn accordance with § 173.22 of the HMR, it is the shipper’s responsibility to properly classify\nhazardous materials, as this Office does not generally perform this function. However, based on\nthe information provided in your letter, it is the opinion of this Office that the description of\n“UN3491, Toxic by inhalation liquid, water-reactive, flammable, n.o.s. (Silylamine compound),\n6.1 (4.3, 8, 3), PG I” is correct. For transport within the United States, § 172.402(a)(2) requires\nall hazardous materials with a Class 8, PG I, subsidiary hazard to be labeled with a subsidiary\n1 Air Liquide USA LLC, Letter of Interpretation Reference Number 13-0003, available at\nhttps://www.phmsa.dot.gov/regulations/title49/interp/13-0003.\n\n<<<PAGE 4>>>\n\nCORROSIVE hazard warning label in all modes of transport. Therefore, the subsidiary hazard\nclass must be entered in the proper shipping description as well (see § 172.202(a)(3)).\nI hope this information is helpful. Please contact us if we can be of further assistance.\nSincerely,\nAlexander Wolcott\nActing Chief, Regulatory Review and Reinvention Branch\nStandards and Rulemaking Division","truncated":false,"body_characters":6462}