{"operation":"document","citation":"26-0050","title":"Koorsen Fire & Security — Hazardous Materials Safety Interpretation","source_type":"guidance","agency":"Pipeline and Hazardous Materials Safety Administration","status":"guidance","official":true,"published_on":"2026-07-28","effective_on":null,"summary":"26-0050 response to Koorsen Fire & Security concerning 173.309, 180.209.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-interpretation-26-0050.json","markdown":"https://regulus.evalyn.ai/document/phmsa-interpretation-26-0050.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-interpretation-26-0050","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/2026-07/26-0050.pdf","body":"<<<PAGE 1>>>\n\n1200 New Jersey Avenue, SE\nWashington, DC 20590\nU.S. Department\nof Transportation\nPipeline and Hazardous\nMaterials Safety\nAdministration\nJuly 28, 2026\nMr. Brick Keltner\nCorporate Shop Trainer\nKoorsen Fire & Security\n2820 N. Webster Ave\nIndianapolis, IN 46219-1013\nReference No. 26-0050\nDear Mr. Keltner:\nThis is in response to your April 27, 2026 letter requesting clarification of the Hazardous\nMaterials Regulations (HMR; 49 CFR Parts 171-180) applicable to the requalification of\nDepartment of Transportation (DOT) specification 4BA and 4BW cylinders used in fire\nsuppression systems that are installed in restaurants, kitchens, or paint booths.\nWe have paraphrased and answered your questions as follows:\nQ1. Does a DOT 4BA or 4BW fire suppression cylinder that has a water capacity over 5.44\nkg (12 pounds) meet the definition of a “fire extinguisher?”\nA1. Yes. A DOT 4BA or 4BW cylinder used in a suppression system meets the definition of a\nfire extinguisher under § 173.309, provided it is charged with either a compressed gas\nand an extinguishing agent, or a gas which comprises the sole fire extinguishing agent.\nSee § 173.309(a)(1)-(5). Note that this definition does not include cylinders pressurized\nwith a gas solely for the purpose of expelling a separately stored extinguishing agent in\nthe fire suppression system.\nQ2. If the answer to Q1 is yes, is a DOT 4BA or 4BW fire suppression cylinder that has a\nwater capacity over 5.44 kg (12 pounds) required to be tested 12 years after the original\ntest date and at 7-year intervals thereafter?\nA2. Yes. Under § 180.209(j)(1)(ii), a DOT 4BA or 4BW cylinder with a water capacity over\n5.44 kg (12 pounds) that meets the definition of a fire extinguisher in § 173.309 must be\nrequalified 12 years after the original test date. If the proof pressure test method is used,\nthe requalification must be performed 12 years after the original test date, and at 7-year\nintervals thereafter. For the water-jacket or direct expansion test, the requalification must\nbe performed by the end of 12 years after the original test date and at 12-year intervals\n\n<<<PAGE 2>>>\n\nthereafter. Alternatively, the cylinder may be requalified in accordance with any of the\nother eligible requalification periods that the cylinder meets in § 180.209.\nQ3. Does a DOT 4BA or 4BW fire suppression cylinder that has a water capacity over 5.44\nkg (12 pounds) installed on a mobile food truck or trailer meet the requirement to be\ntested 12 years after the original test date and at 7-year intervals thereafter?\nA3. Yes. The HMR classification of a cylinder as a fire extinguisher for transportation\npurposes under § 173.309 is based on its configuration and function (i.e., being installed\nas part of a fire suppression system). Therefore, a qualifying cylinder installed on a\nmobile food truck or trailer may follow the same 12-year initial and 7-year or 12-year\nsubsequent requalification intervals, depending on requalification test method under\n§ 180.209(j), as a system installed in a fixed building or any other configuration it may be\nin when not in transportation.\nQ4. Do the provisions applicable to fire suppression systems apply to both wet and dry\nchemical suppression systems (e.g., wet chemical in kitchens/restaurants and dry\nchemical in paint booths)?\nA4. Yes. The definition of a fire extinguisher in the introductory text to § 173.309 does not\ndifferentiate between the types of chemical agents used, provided the cylinder is charged\nwith a compressed gas and an extinguishing agent (wet or dry chemical) or a gas that\nserves as the sole extinguishing agent.\nI hope this information is helpful. Please contact us if we can be of further assistance.\nSincerely,\nAlexander Wolcott\nActing Chief, Regulatory Review & Reinvention\nStandards and Rulemaking Division\n\n<<<PAGE 3>>>\n\nPollack, A.\n26-0050\nMr. Shane Kelley\nDirector, Standards and Rulemaking Division\nU.S. DOT/PHMSA (PHH-10)\n1200 New Jersey Avenue, SE East Building, 2nd Floor\nWashington, DC 20590\nBrick Keltner\nCorporate Shop Trainer\nKoorsen Fire & Security\n2820 N. Webster\nIndianapolis, In 46219\nTelephone 317-225-4 785\nEmail: brick.keltner@koorsen.com\nMr. Kelley, I would like a Formal Interpretation of 49 CFR 180.209U). Cylinder used as a\nFire Extinguisher.\nThe questions that I have relate to the testing of Fire Extinguishers as well as\nthe definition of them. In the above standard it states the time frame of the testing\nintervals.\nIn around July - August 2021 the Transportation of Restaurant/ Kitchen and Dry\nChemical Suppression System cylinders was changed to - transport them as UN1044\nFire Extinguishers. I requested a Formal Interpretation (ref# 21-0084) if they were also\nto be tested as Fire Extinguishers. The answer I received back was, NO - they are not\nto be tested as Fire Extinguishers, it is just for Transportation.\nReferences are from the November 1 , 2025 - 49 CFR MasterRegs\n180.209U) states the requirements for testing of Fire Extinguishers and references\n173.309(a) for the definition of a Fire Extinguisher.\n173.309 - Fire Extinguishers\nThis section applies to portable fire extinguishers for manual handling and\noperation, fire extinguishers for installation in aircraft, fire extinguishers for installation\nas part of a fire suppression system, and large fire extinguishers. Fire Extinguishers for\ninstallation as part of a fire suppression system include cylinders charged with either a\ncompressed gas and an extinguishing agent in the system or a gas which comprises the\nsole fire extinguishing agent in the system.\n\n<<<PAGE 4>>>\n\n180.2090) - states that only DOT cylinders used as a fire extinguisher in conformance\nwith 173. 309( a) of this subchapter may be requalified in conformance with this\nparagraph 0).\n180.2090)(1) A DOT 48, 48A, 48240ET or 48W cylinder used as a fire extinguisher\nmay be tested as follows:\n(ii) For a cylinder having a water capacity over 5.44kg (12 pounds), by the waterjacket,\ndirect expansion or proof pressure test methods as prescribed in CGA C-1. For\nproof pressure test, a requalification must be performed by the end of 12 years after the\noriginal test date and at seven (7) year intervals.\nThe questions are\nDoes a 48A and/or 48W Restaurant / Kitchen / Paint Booth Suppression\ncylinder that has a water capacity over 5.44kg (12 pounds) meet the\ndefinition of Fire Extinguisher and require to be tested 12 years after the\noriginal test date and at 7 years after that?\n- Does a 48A and/or 48W Restaurant Suppression cylinder that has a water\ncapacity over 5.44kg (12 pounds) and is installed on a mobile Food Truck /\nTrailer meet the requirement to be tested 12 years after the original test date\nand at 7 years after that?\n- Does this apply to both Wet & Dry Chemical Suppression Systems. (i.e. wet\nchemical - Kitchen/Restaurant as well as dry chemical - Paint Booths)\nThank you for any information that you can give me. Brick Keltner, Koorsen Fire &\nSecurity","truncated":false,"body_characters":6947}