{"operation":"document","citation":"25-0108","title":"DG Advisor — Hazardous Materials Safety Interpretation","source_type":"guidance","agency":"Pipeline and Hazardous Materials Safety Administration","status":"guidance","official":true,"published_on":"2025-12-11","effective_on":null,"summary":"25-0108 response to DG Advisor concerning 172.102, 173.22.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-interpretation-25-0108.json","markdown":"https://regulus.evalyn.ai/document/phmsa-interpretation-25-0108.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-interpretation-25-0108","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/2025-12/250108.pdf","body":"<<<PAGE 1>>>\n\nU.S. Department\nof Transportation\nPipeline and Hazardous\nMaterials Safety\nAdministration\n1200 New Jersey Avenue, SE\nWashington, DC 20590\nDecember 11, 2025\nBen Barrett\nDG Advisor\n6 Starry Way\nP.O. BOX 248 Dubois,\nWY 82513\nReference No. 25-0108\nDear Mr. Barrett:\nThis letter is in response to your August 4, 2025 letter and previous conversations with PHMSA\nstaff requesting clarification of the provisions of the Hazardous Materials Regulations (HMR;\n49 CFR Parts 171-180) applicable to the classification of a hazardous material. Your client has\ndeveloped a new agricultural fertilizer compound consisting of 69.5 percent ammonium nitrate,\n30.5 percent ammonium phosphate, and no combustible substances. It is your understanding that\nthis mixture is not regulated as a hazardous material because in accordance with the flowchart in\nSection 39.5 of the United Nations (UN) Manual of Tests and Criteria—Section 39.5—titled\n“Classification criteria” (which is incorporated by reference in the HMR), analysis of the\nfertilizer’s properties leads to box 26 which states it is “Not classified.” You seek confirmation\nthat the mixture as described is not regulated as a hazardous material.\nIn accordance with § 173.22 of the HMR, it is the shipper’s responsibility to properly classify a\nhazardous material, as this Office does not generally perform this function. However, based on\n\n<<<PAGE 2>>>\n\nthe information provided in your letter, it is the opinion of this Office that the agricultural\nfertilizer you have described is not regulated as a hazardous material. This is based on our\nunderstanding that the company classified its material in accordance with § 172.102, special\nprovision 132, and followed the decision logic and required testing in the UN Manual of Tests\nand Criteria, 7th revised edition, as described in your incoming letter.\nI hope this information is helpful. Please contact us if we can be of further assistance.\nSincerely,\nDirk DerKinderen\nChief, Standards Development Branch\nStandards and Rulemaking Division\n\n<<<PAGE 3>>>\n\nBaker, Y.\n25-0108\nBENJAMIN Y. BARRETT, PE\nMARIE-FRANCE DAGENAIS, LL.L\nKYLE D. BARRETT, JD\nADAM BURKS, MBA\n6 STARRY WAY\nP.O. BOX 248\nDUBOIS, WY 82513 USA\nPHONE: +1 (307) 455-2517\nWWW.DGADVISOR.COM\n8/4/25\nStandards and Rulemaking Division\nPipeline and Hazardous Materials Safety Administration\nU.S. Department of Transportation\n1200 New Jersey Avenue, SE, East Building\nWashington, DC 20590-0001\nTo Whom it May Concern:\nI’m writing to kindly request a letter of interpretation to answer the question presented below.\nDefuse Technologies, LLC (Defuse) is a company based in Birmingham, Alabama, that\nresearches and provides solutions for agricultural fertilizers. Defuse recently developed a new\nammonium nitrate-based fertilizer (DAN) that eliminates the explosive characteristics of\nammonium nitrate (AN) while maintaining the agricultural benefits of AN for crop growth.\nWe met recently with PHMSA staff to discuss the proper classification of this product, and we\nwould like to confirm our understanding of the regulations. This material contains 69.5% ammonium\nnitrate and 30.5% ammonium phosphate (a fire retardant used to extinguish forest fires). It is our\nunderstanding that this mixture is not regulated as a dangerous good, as it takes the following path\nthrough the classification criteria of Section 39.5 of the UN Manual of Tests & Criteria, incorporated\nby reference into the CFR.\nThe path that was tentatively chosen with PHMSA in our meeting is as follows:\n1. Figure 39.1(a) Classification criteria for solid ammonium nitrate based fertilizers.\na. b. c. Box 1 – Defuse’s product, DAN, is a fertilizer. Proceed to Box 2.\nBox 2 – DAN contains 69.5% ammonium nitrate. Proceed to Box 10.\nBox 10 – “Go to figure 39.1(b)”. Proceed to Box 11.\n2. Figure 39.1(b) Classification criteria for solid ammonium nitrate based fertilizers\n(continued)\na. Box 11 – “(arrive) from figure 39.1(a)”. Proceed to Box 12.\nb. Box 12 – DAN is an ammonium nitrate-based compound fertilizer. It contains\nnitrogen and phosphorus. Proceed to Box 13.\nc. Box 13 – DAN contains 69.5% ammonium nitrate, less than 70%. Proceed to Box\n21.\nDG Advisor, LLC • PO Box 248 • Dubois WY 82513 USA • +1 816 853 3508 • ben.barrett@dgadvisor.com\n\n<<<PAGE 4>>>\n\nDOT LOI Request Page 2 of 2\nd. Box 21 – DAN contains 69.5% ammonium nitrate, greater than 45%. Proceed to\ne. f. g. h. Box 22.\nBox 22 – DAN contains no combustible substances, i.e., less than 0.4%. It\nconsists of ammonium nitrate and ammonium phosphate, which combine into a\nhomogenous mixture of ammonium phosphate nitrate compounds. Proceed to Box\n24.\nBox 24 – DAN passed the UN S.1 Trough Test and is not capable of self-\nsustaining decomposition. Proceed to Box 26.\nBox 26 – “Not Classified.”\nThus, DAN is Not Regulated in Class 1.\nBased on the foregoing information, please clarify whether Defuse Ammonium Nitrate is\nregulated by the Department of Transportation Pipeline and Hazardous Materials Safety\nAdministration).\nThank you for your consideration,\nBen Barrett\nAttachments: 1. MTC Figure 39.1 Charts\nDG Advisor, LLC • PO Box 248 • Dubois WY 82513 • USA • +1 816 853 3508 • ben.barrett@dgadvisor.com\n\n<<<PAGE 5>>>\n\nCopyright © United Nations, 2023. All rights reserved.\nSECTION 39\nCLASSIFICATION PROCEDURE AND CRITERIA RELATING TO SOLID\nAMMONIUM NITRATE BASED FERTILIZERS\n39.1 Purpose\nThis section presents the United Nations scheme for the classification of solid ammonium\nnitrate based fertilizers as referred to in the Model Regulations, chapter 3.3, special provisions 307 and 193.\n39.2 Scope\nAny new solid fertilizer composition containing ammonium nitrate shall be subjected to the\nclassification procedure as set out in 39.4.\n39.3 Definitions\n39.3.1 An ammonium nitrate based fertilizer is a uniform mixture containing ammonium (NH4\n+) and\nnitrate (NO3−) ions. See also 39.3.3.\n39.3.2 A compound fertilizer is a uniform mixture that contains at least two of the three primary\nnutrients nitrogen (N), phosphorus (P) and potassium (K).\n39.3.3 In determining the ammonium nitrate content, all nitrate ions for which a molecular equivalent\nof ammonium ions is present in the fertilizer shall be calculated as ammonium nitrate.\n39.3.4 carbon.\nCombustible substances as referred to in paragraph 39.4 include also inorganic substances that\ncan be oxidized, e.g. elemental sulphur. For organic substances the content of combustibles is calculated as\n39.3.5 Materials that may be incompatible with ammonium nitrate include urea, acids,\nsuperphosphates with free acid, elemental sulphur, sulphides and most transition metals, including heavy\nmetals (e.g. copper), and chlorides. Note however that this listing is not exhaustive.\n39.4 Classification procedure\n39.4.1 Solid ammonium nitrate based fertilizers are classified on the basis of their composition and\nexperience and knowledge of their hazardous behaviour. Occasionally, the classification is complemented by\ntesting for the ability to undergo self-sustaining decomposition or for explosive properties. These principles\nare condensed in the flowchart in 39.5.\n39.4.2 UN 2067 may only be used for ammonium nitrate based fertilizers that do not show explosive\nproperties when tested in accordance with test series 2 of this Manual.\n39.4.3 Ammonium nitrate based fertilizers that do not fulfil the requirements for classification as\nUN 2067, can be assigned another suitable UN number in Class 1 or Class 5, Division 5.1, provided that the\nsuitability for transport is demonstrated and this is approved by the competent authority. This may for instance\nbe when contamination has occurred in e.g. an accident, so that the fertilizer can be transported under a suitable\nUN number e.g. in Class 1 as approved by the competent authority.\n39.4.4 Ammonium nitrate based fertilizers that meet composition limits relevant for inclusion in the\nclass of Explosives as set out in 39.5 shall be classified in that class regardless of the results when tested in\naccordance with test series 2 of this Manual.\n- 445 -\n\n<<<PAGE 6>>>\n\nCopyright © United Nations, 2023. All rights reserved.\n39.4.5 Ammonium nitrate based fertilizers that meet composition limits relevant for classification as\noxidizing solids as set out in 39.5, or are otherwise classified as oxidizing solids, shall not be exempted from\nthat classification on the basis of the results from tests O.1 and/or O.3 in section 34 of this Manual. See also\nparagraph 34.3.1 in section 34 of this Manual.\n39.4.6 Fertilizers that contain 70 % or more ammonium nitrate shall not contain ammonium sulphate\nas nutrient, unless they are compound fertilizers with less than 90 % ammonium nitrate and with at least 10 %\ninorganic materials excluding ammonium nitrate and ammonium sulphate.\n39.4.7 Compound fertilizers that meet the composition limits relevant for potential inclusion for\ntransport in Class 9 shall be tested for their capability to undergo self-sustaining decomposition according to\nthe method given in paragraph 38.2.4 of this Manual (test S.1, trough test) and classified according to criteria\ngiven there and in 39.5.\n39.5 Classification criteria\n39.5.1 Ammonium nitrate based fertilizers shall be classified in accordance with the flowchart below.\nFigure 39.1 (a): Classification criteria for solid ammonium nitrate based fertilizers\n1\nFERTILIZER FOR\nCLASSIFICATION\n2\nNot within the composition\nlimits of UN 2067\n(see 39.4.3)\n6\nYes\nDoes it contain\n% ammonium\nnitrate?\nDoes it contain\n3 4\nany incompatible materials\nYes Yes\nin amounts that could negatively\naffect the stability of\nammonium nitrate?\n(see 39.3.5)\nNo\n5\nNo\nDoes it\ncontain > 0.2 %\ncombustible\nsubstances?\n(see 39.3.4)\nNo\nDoes it\ncontain > 5 %\nammonium sulphate?\n(see 39.4.6)\nNo\nNot within the composition\nlimits of UN 2067.\nClassify as explosive.\n(see 39.4.4)\n8\n10\n7\n9\nYes\nNot within the composition\nlimits of UN 2067\n(see 39.4.3)\nGo to figure 39.1 (b)\nClassify as UN 2067\n(see 39.4.2 and 39.4.5)\n- 446 -\n\n<<<PAGE 7>>>\n\nCopyright © United Nations, 2023. All rights reserved.\nFigure 39.1 (b): Classification criteria for solid ammonium nitrate based fertilizers (continued)\n11\nFrom figure 39.1 (a)\n15\nIs it\n12 13 14\nYes\nDoes it\nDoes it contain\nYes Yes\na compound\ncontain > 70 %\n> 0.4 % combustible\nfertilizer containing\nammonium\nsubstances?\nammonium nitrate?\nnitrate?\n(see 39.3.4)\n(see 39.3.2)\nNo\nNo\nNo\nDoes it\nDoes it\n16 17\ncontain 10 %\ncontain\nYes Yes\ninorganic materials\n> 5 % ammonium\nexcluding ammonium nitrate\nsulphate?\nand ammonium\n(see 39.4.6)\nsulphate ?\nNo\nNo\n19 20\nNot within the\ncomposition limits of\nUN 2067 or UN 2071\n(see 39.4.3)\n18\nClassify as\nUN 2067\n(see 39.4.2 and\n39.4.5)\nClassify as UN 2067.\n(see 39.4.2 and 39.4.5)\nNot within the\ncomposition limits of\nUN 2067 or UN 2071\n(see 39.4.3)\n23\n27\nGo to figure 39.1 (c)\n21 22\nDoes it\nDoes it contain\nYes Yes\ncontain %\n> 0.4 % combustible\nammonium\nsubstances?\nnitrate?\n(see 39.3.4)\nNo\n24\n26\nNo\nIs it capable\nof self-sustaining\ndecomposition?\n(see 39.4.7)\nNo\nNot within the\ncomposition limits of\nUN 2067 or UN 2071\n(see 39.4.3)\n25\nYes\nClassify as UN 2071\n(see 39.4.7)\nNot classified\n- 447 -","truncated":false,"body_characters":11115}