{"operation":"document","citation":"25-0089","title":"Day & Zimmermann — Hazardous Materials Safety Interpretation","source_type":"guidance","agency":"Pipeline and Hazardous Materials Safety Administration","status":"guidance","official":true,"published_on":"2026-03-27","effective_on":null,"summary":"25-0089 response to Day & Zimmermann concerning 172.300.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-interpretation-25-0089.json","markdown":"https://regulus.evalyn.ai/document/phmsa-interpretation-25-0089.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-interpretation-25-0089","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/2026-04/25-0089.pdf","body":"<<<PAGE 1>>>\n\nU.S. Department\nof Transportation\nPipeline and Hazardous\nMaterials Safety\nAdministration\n1200 New Jersey Avenue, SE\nWashington, DC 20590\nMarch 27, 2026\nMr. Matthew Behrens\nDirector, ATF and Export/Import Compliance\nDay & Zimmermann\n3975 Virginia Mallory Drive, Suite 200\nChantilly, VA 20151\nReference No. 25-0089\nDear Mr. Behrens:\nThis is in response to your June 26, 2025 letter requesting clarification of the\nHazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to\nmarking packages containing explosives. Specifically, you seek clarification on\n§ 172.320(b)(1) which states that in lieu of an EX-number a package of a Class 1\nmaterials may be marked with a national stock number (NSN) issued by the\nDepartment of Defense (DoD) or identifying information, such as a product code\nrequired by regulations for commercial explosives specified in 27 CFR part 555, if\nthe national stock number or identifying information can be specifically associated\nwith the EX-number assigned.\nWe have paraphrased and answered your questions as follows:\nQ1. With respect to § 172.320(b)(1), under what specific circumstances or\nconditions does PHMSA authorize the use of alternate markings in lieu of an\nEX number?\nA1. Section 172.320(b)(1) authorizes the use of alternative markings in lieu of an\nEX number when the package is marked with a NSN issued by the DoD or\nidentifying information, such as a product code required by regulations for\ncommercial explosives specified in 27 CFR part 555.\nQ2. Can an Alcohol Tobacco and Firearms (ATF) approved coding system, such\nas a lot numbering system authorized through a marked variance or an NSN\n\n<<<PAGE 2>>>\n\nbe used as the required identification information associated with the EX\nnumber?\nA2. Yes. An approved ATF coding system through an NSN is permissible\nprovided it is specifically associated with the EX number.\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\n\n<<<PAGE 3>>>\n\nCajar, J.\n25-0089\nFrom: INFOCNTR (PHMSA)\nTo: Baker, Yul (PHMSA)\nCc: Hazmat Interps\nSubject: FW: Request for Letter of Interpretation - 49 CFR §172.320(b)(1)\nDate: Friday, June 27, 2025 10:50:09\nAttachments: DOT Letter of Interpretation .pdf\nHi Yul,\nPlease see the below interpretation request. Let us know if you need anything.\nSincerely,\nJanaye\nFrom: Behrens, Matthew <Matthew.Behrens@soc-usa.com>\nSent: Thursday, June 26, 2025 3:46 PM\nTo: PHMSA HM InfoCenter <PHMSAHMInfoCenter@dot.gov>\nSubject: Request for Letter of Interpretation - 49 CFR §172.320(b)(1)\nYou don't often get email from matthew.behrens@soc-usa.com. Learn why this is important\nCAUTION: This email originated from outside of the Department of Transportation (DOT). Do\nnot click on links or open attachments unless you recognize the sender and know the content\nis safe.\n(PDF Attached of email)\nDear PHSMA representative,\nDay & Zimmermann, Inc. respectfully requests a formal letter of interpretation regarding\ncompliance with 49 CFR §172.320(b)(1). Specifically, we seek clarification on marking\npackaging \"in lieu of an EX number, a national stock number issued by the Department of\nDefense or identifying information, such as a product code required by regulations for\ncommercial explosives specified in 27 CFR part 555, if the national stock number or identifying\ninformation can be specifically associated with the EX number assigned”.\nIn reviewing §172.320(b)(1), our understanding is that under certain conditions, it may be\npermissible to mark packages in a manner other than using an EX number issued by PHMSA.\nWe seek clarification from PHMSA on the following points:\nUnder what specific circumstances or conditions does PHMSA authorize the use of\nalternate markings \"in lieu of an EX number\"?\nCan and approved ATF coding system through a “marking variance” or an NSN be used\nfor scenarios described below?\n\n<<<PAGE 4>>>\n\nThe subsidiaries of Day & Zimmermann, Inc. (DZI)—namely American Ordnance, Day &\nZimmermann Lone Star, and Day & Zimmermann Kansas—specialize in the production of\nexplosive materials for both the Department of Defense and the commercial sector. Every\nfacility holds a Federal Explosives License, granting them the legal authority to partake in\nnumerous activities related to explosives, including importing, manufacturing, and trading in\nexplosive materials. They must also maintain consistent adherence to their EX number, which\nis a prerequisite for handling explosives categorized under Hazard Class 1. Regulation 49 CFR\n§172.320(b)(1) outlines the marking requirements for the transportation of explosive\nhazardous materials, placing particular emphasis on alternatives to the use of an EX (explosive\napproval) number.\nRegulation Text:\n\"(b) Except for fireworks, in lieu of the EX number, packaging containing explosive substances\nand articles may be marked with:\n1. A national stock number issued by the Department of Defense; or identifying\ninformation, such as a product code required by regulations for commercial explosives\nspecified in 27 CFR part 555, if the national stock number or identifying information can\nbe specifically associated with the EX number assigned.\"\nInterpretation:\nNational Stock Number (NSN): A number assigned by the U.S. Department of Defense\n(DoD) for explosives designated for military or defense-related purposes.\nIdentifying Information (Product Code):\nInformation, such as a product code defined in 27 CFR part 555, which pertains to\ncommercial explosives regulated by the Bureau of Alcohol, Tobacco, Firearms, and Explosives\n(ATF).\nDZI key condition:\nTo use these alternatives, DZI subsidiaries must ensure that this alternative number or code\ncan be clearly associated or traced back to the originally assigned EX number. This means the\nNSN or product code is not random—it must correspond explicitly and verifiably to a valid EX\napproval number that PHMSA previously issued.\nWould this scenario apply to 49 CFR §172.320(b)(1)?\n\n<<<PAGE 5>>>\n\nOn certain occasions when manufacturing explosives for the DoD, there are explosives that\nsome contracts may allow the contractor to retain excess or rejected explosive materials for\ntheir own use, for sale in commerce.\nThe excess explosive materials were manufactured under a DoD contract and a Government-\nSpecific EX number was issued.\nA company cannot use a U.S. Government (USG) EX number to ship commercial\nexplosives for non-government purposes.\nUSG EX numbers are specific to U.S. government-owned, government-developed, or\ngovernment-contracted explosives.\nPHMSA rules prohibit government EX numbers for private commercial distribution\nThe only scenario where a USG EX number might be used in commercial transport is if a\ncompany is acting as a contractor shipping explosives exclusively for the government\nunder a government contract, and the shipment is part of that government program.\nAlternative Situations:\nSpecifically, to excess explosives manufactured under the DoD, a company would apply\n49 CFR §172.320(b)(1) and instead of an EX number to ship the explosives in\ncommercial commerce, the company would use an NSN that clearly linked to an existing\nEX number would be used.\nThis alternative would not apply to commercially manufactured explosives that were\nnot under a USG contract and would require an EX number because there is no NSN\nclearly linked to a non-USG explosive.\nOr\nA commercial explosives manufacturer that adheres to ATF product codes (per 27 CFR\nPart 555) can mark containers with the product code instead of the EX number,\nprovided the product code directly corresponds with an assigned EX number.\nAll commercial explosives must be marked in accordance with 555.109(c)(5)\nIdentification of explosive materials (USG is exempt):\nA coding system and omit printed markings on the container that show all the\nrequired information.\nThe Director must approve the application before the proposed coding can be\nused.\nThis coding system is allowed to Federal Explosive Licensees by means of a\n“marking variance”.\n\n<<<PAGE 6>>>\n\nAll DZI subsidiaries have approved marking variance that allow a coding system\nusing the MIL-STD-1168C - Lot Numbering.\nATF approved Lot Number coding:\nAO25D018-013B\nA. Manufacturers identification symbol\nB. C. Two-digit numeric code for the year of production\nA single alpha code signifying the month of production\nD. Lot interfix number\nE. Lot sequence number\nF. Lot suffix number\nThe lot number is a unique code number assigned to a quantity or batch of a single\nammunition end item (complete round, major component, propellants, etc.) which are\nmanufactured or assembled by one producer under uniform conditions, and which is\nexpected to function in a uniform manner.\nEnsures that inspectors or authorities can trace the shipment back to the manufacturer\nand gives all information to what the explosive is.\nThe lot number is a unique code number assigned to a quantity or batch of a single\nammunition end item (complete round, major component, propellants, etc.) which are\nmanufactured or assembled by one producer under uniform conditions, and which is expected\nto function in a uniform manner. Ensures that inspectors or authorities can trace the shipment\nback to the manufacturer and gives all information to what the explosive is.\nOur intent is to ensure full compliance with federal hazardous materials regulations, and we\nseek authoritative guidance to support our operations.\nThank you very much for your attention and guidance on this matter. We look forward to your\nresponse and clarification\nRespectfully,\nMatthew Behrens\nDirector, ATF and Export/Import Compliance\nDay & Zimmermann\nM 3864065087\n3975 Virginia Mallory Drive, Suite 200 | Chantilly, VA 20151\n\n<<<PAGE 7>>>\n\nMason & Hanger| SOC","truncated":false,"body_characters":9847}