{"operation":"document","citation":"24-0042","title":"Tym’s LLC — Hazardous Materials Safety Interpretation","source_type":"guidance","agency":"Pipeline and Hazardous Materials Safety Administration","status":"guidance","official":true,"published_on":"2025-06-26","effective_on":null,"summary":"24-0042 response to Tym’s LLC concerning 173.25, 173.301.","machine_formats":{"json":"https://regulus.evalyn.ai/document/phmsa-interpretation-24-0042.json","markdown":"https://regulus.evalyn.ai/document/phmsa-interpretation-24-0042.md"},"app_url":"https://regulus.evalyn.ai/document/phmsa-interpretation-24-0042","source_url":"https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/2025-06/240042.pdf","body":"<<>>\n\n1200 New Jersey Avenue, SE\nWashington, DC 20590\nU.S. Department\nof Transportation\nPipeline and Hazardous\nMaterials Safety\nAdministration\nJune 26, 2025\nBrian Tyminski\nPresident and CEO\nTym’s LLC\n721 Depot Drive\nAnchorage, AK 99501\nReference No. 24-0042\nDear Mr. Tyminski:\nThis letter is in response to your June 4, 2024 email and subsequent emails and a phone call\nrequesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180)\napplicable to marking and labeling requirements for aviation cylinders (i.e., cylinders used on\naircraft). Specifically, you present a scenario where it is your understanding that required\nmarkings and labels cannot be placed on Department of Transportation (DOT) specification\ncylinders packed in a strong non-bulk outer container because the cylinders are a component of a\n14 CFR-approved aircraft part.\nWe have paraphrased and answered your questions as follows:\nQ1. Is placing DOT 3AA specification cylinders in a strong non-bulk outer container (e.g., a\nfiberboard box) considered a combination package for purposes of the HMR? If so, can\nthe DOT 3AA specification cylinder be transported without markings or labels in\naccordance with Part 172, Subparts D and E, respectively, if the strong non-bulk outer\npackaging is marked and labeled?\nA1. No. The configuration described is not a combination package. DOT 3AA cylinders are\nconsidered a single packaging and therefore must be marked and labeled appropriately.\nDOT specification cylinders not specifically listed in § 173.301(a)(9)—such as DOT\n3AA cylinders—that are further packed in an outer container such as a fiberboard box is\nnot a combination package and would be considered an overpack configuration subject to\nthe requirements found § 173.25.\nQ2. Is placing DOT 3HT specification cylinders in a strong non-bulk outer container (e.g., a\nfiberboard box) considered a combination package for purposes of the HMR? If so, can\nthe DOT 3HT specification cylinder be transported without markings and labels in\n\n<<>>\n\naccordance with Part 172, Subparts D and E, respectively, if the outside of the\ncombination package is marked and labeled?\nA2. Yes. DOT 3HT specification cylinders are listed in § 173.301(a)(9) and are required to be\npackaged in a “strong outer packaging.” This combination package configuration requires\nmarking and labeling of the outer packaging and does not necessitate marking and\nlabeling the DOT 3HT cylinder. Furthermore, in accordance with § 173.301(a)(9), the\noutside of the combination packaging must be marked with an indication that the inner\npackagings (e.g., DOT 3HT cylinders) conform to the prescribed specifications.\nFor an explanation of 14 CFR requirements as it relates to DOT specification cylinders\ninstalled on aircraft and whether they may display Part 172, Subpart D and E marks and labels,\nplease contact the Federal Aviation Administration (FAA) at hazmatinfo@faa.gov.\nI hope this information is helpful. Please contact us if we can be of further assistance.\nSincerely,\nDirk Der Kinderen\nChief, Standards Development Branch\nStandards and Rulemaking Division\n\n<<>>\n\nRoundtree\n24-0042\nJones, Jessie Jane CTR (PHMSA)\nFrom: Kelley, Shane (PHMSA)\nSent: Subject: Attachments: Tuesday, June 4, 2024 7:16 PM\nTo: Hazmat Interps\nFwd: Letter of Interpretation Request: Overpack for Aviation Cylinders\nLetter of Intrep 24-0010 5-10-2024.pdf; 20240604 OVERPACK marking request for\ninterpretation Tyms LLC.pdf\nPlease process and thank you.\nShane C. Kelley\nDirector, Standards and Rulemaking\nOffice of Hazardous Materials Safety\nPipeline and Hazardous Materials Safety Administration\nU.S. Department of Transportation\nOfffice: (202) 366-8553\nMobile: (202) 308-4312\nFrom: Brian Tyminski \nSent: Tuesday, June 4, 2024 7:03:43 PM\nTo: pipeline_interp_submittal \nCc: Kelley, Shane (PHMSA) ; Burger, Donald (PHMSA) ; Tom Ferguson\n\nSubject: Letter of Interpretation Request: Overpack for Aviation Cylinders\nCAUTION: This email originated from outside of the Department of Transportation (DOT). Do not click on links\nor open attachments unless you recognize the sender and know the content is safe.\nGood afternoon,\nPlease see the attached request for a Letter of Interpretation for 49 CFR 173.301(a), 173.25(a), 178.35,\n178.47, 171.8. This was produced, in part, in response to the Letter of Interpretation Reference No. 24-\n0010 dated May 10, 2024. That letter unfortunately opened additional questions raised by the aviation\nindustry when shipping common oxygen and fire bottles containing compressed gases.\nThis request serves to support the operations of aircraft repair stations and aircraft owners, operators,\nand parts distributors, in addition to our own shipping operations.\nI have cc'd in the Council on the Safe Transportation of Hazardous Articles (COSTHA) as a member\norganization and for the benefit of the many airline and air repair station members affected by the issue\npresented.\nOur official request is attached as a formal letter.\nBelow, please find a summary of the problem faced by industry, written for the layman, in order to gain\ninsight on the regulatory clarifications described in the request to assist you with processing the\nattached request.\n1\n\n<<>>\n\nProblem:\nAll DOT specification cylinders 2P, 2Q, 3E, 3HT, 4BA, 4D, 4DA, 4DS, and 39 and many Special Permit\ncylinders are required to be placed in a strong outer containers (box, crate, etc.) when shipped. This is\nin accordance with 49 CFR § 173.301(a)(9), which is the law the dictates how gasses and all other\nHazardous Materials in cylinders must be shipped. Manufacturing Special Permits (SP), such as DOT-\nSP 7945 and DOT-SP 8495, also list this law as a requirement within the SP document, so they must be\npackaged the same way.\nConfusion has plagued the industry because carriers like Federal Express (FedEx) require all gas\ncylinders, of any type, to be packed in specific types of strong outer containers. Although it is not\nfederal law, these carriers will not pick up or deliver shipments of gas cylinders unless they are\nprotected with additional packaging.\nSpecifically, carriers like FedEx are looking for an “OVERPACK” marking on the outer-most box. This\nindicates to the carrier that the package meets the policy requirements. If this word does not appear,\nsome carriers will reject and return your package for non-compliance, even though it complies fully\nwith federal laws.\nThe problem is that the word “OVERPACK” is a marking that may only be applied to the package if it\nmeets the stringent requirements of 49 CFR 173.25, which is the federal law that dictates when and\nhow this marking should be applied. Simply, the OVERPACK marking may not be applied if the package\nis not an overpack. This was recently solidified in a DOT Letter of Interpretation Reference No. 24-0010\ndated May 10, 2024.\nThe problem is that all aviation compressed gas cylinders such as oxygen bottles, fire extinguishers,\nand fire bottles, while legal to ship, may not comply with the requirements to mark OVERPACK on the\nouter container. They are shipped properly in a combination of packaging that includes the component\n(with a cylinder attached) in addition to outer packaging such as boxes, crates, or ATA 300\nspecification containers. Therefore, they are packaged properly per federal law but are being rejected\ndue to inappropriate application of carrier policy.\nThe above-mentioned Letter of Interpretation Reference No. 24-0010 was written to solve this problem\nand ensure that the carrier understood that the shipments were both legal to ship, safe to carry, and\ncompliant with internal policies.\nUnfortunately, the lack of detail in the request and very detailed response by the DOT made the\nproblem even worse.\nIt could be inferred by the DOT response that all specification cylinders require the OVERPACK\nmarking and Special Permit cylinders do not. We do not believe this is accurate based on the rules in\n2\n\n<<>>\n\n49 CFR § 173.301(a), 173.25(a), 178.35, 178.47, and 171.8. Doing so may be a violation, and if so, will\nlead to enforcement action, fines, and other penalties for shippers and carriers merely trying to do the\nright thing.\nAdditional information is needed to clarify the situation to remove the confusion, once and for all.\nBest Regards,\nBrian Tyminski\nTym's LLC\n721 Depot Drive\nAnchorage, AK 99501\n+1-425-200-5355\nBrian@tymsllc.com\n3\n\n<<>>\n\nTym’s LLC\n721 Depot Drive\nAnchorage, AK 99501 USA\n+1-425-200-5355\nwww.tymsllc.com\nJune 4, 2024\nOffice of Pipeline Safety (PHP–30) PHMSA\nU.S. Department of Transportation\n1200 New Jersey Avenue SE.\nWashington, DC 20590–0001\npipeline_interp_submittal@dot.gov\nTo Whom it May Concern:\nWe are writing for clarification on the Letter of Interpretation Reference No. 24-0010 dated May 10,\n2024, in addition to 49 CFR 173.301(a), 173.25(a), 178.35, 178.47, 171.8, and DOT-SP 12726. The Letter\nof Interpretation is attached.\nWe are requesting further clarification regarding Answer “A4” of the Letter of Interpretation which\nstates:\n…when the SP requires the use of a strong outer packaging—as in DOT-SP 7945 paragraph 8.g.\nor DOT-SP 8495 paragraph 8.g.—the outer packaging does not meet the definition of an\noverpack, and therefore, “OVERPACK” is not an appropriate marking.\nAlso note, DOT-SP 12726 paragraph 7.a. authorizes the use of both non-DOT specification\ncylinders and DOT specification cylinders, and—when DOT specification cylinders are used—the\n“OVERPACK” marking is required unless the markings representative of each package type\ncontained in the overpack are visible from outside of the overpack.\nPlease note that DOT-SP 7945 paragraph 8f (not 8g) states: “The cylinder must be shipped in strong\noutside packagings in accordance with 173.301(a)(9)” and that DOT-SP 8495 paragraph 8g states\nsimilarly: “The cylinders must be shipped in strong outside packagings in accordance with\n173.301(a)(9).”\nWe understand and agree that Overpack must be used “when specification packagings are required” in\naccordance with 49 CFR 173.25(a)(4). We appreciate how your answers explain that no Overpack should\nbe used for Special Permit cylinders based on the fact that the SP requires “strong outside packagings”\nwith a specific reference to 173.301(a)(9), which is reserved for specification 2P, 2Q, 3E, 3HT, 4BA, 4D,\n4DA, 4DS, and 39 cylinders.\nIn other words, the Special Permit cylinders mentioned in the letter (DOT SP-7945, DOT SP-8495) cannot\nbe offered for transportation in a single packaging because the Special Permits state an outer packaging\nis a requirement based on 173.301(a)(9). If an outer packaging is required, it is not an Overpack because\n\n<<>>\n\nthe inner packaging cannot be offered for transportation by itself. That is, a combination package must\nalways be used for these types of cylinders. Is that correct?\nYour response refers to specification cylinders 3HT, 4DS, and 4DA (4DA by reference to DOT SP-12726).\nYour office states that these require Overpack because they are specification cylinders and based on the\nplain language of 49 CFR 173.25(a)(4) which states “The overpack is marked with the word “OVERPACK”\nwhen specification packagings are required,” they are required to be marked as an Overpack. It is\nobvious that when in some “strong non-bulk outer packagings” (i.e. fiberboard boxes, crates, etc.) “the\nrequired markings representative of each package type contained in the overpack” (i.e. cylinder\nspecification marking, labeling, etc.) will not be “visible from outside of the overpack” and that is why an\nOverpack must be used. Is that correct?\nWe have additional questions regarding 49 CFR 173.301(a)(9) which states:\nSpecification 2P, 2Q, 3E, 3HT, spherical 4BA, 4D, 4DA, 4DS, and 39 cylinders must be packed in\nstrong non-bulk outer packagings. The outside of the combination packaging must be marked\nwith an indication that the inner packagings conform to the prescribed specifications.\nIt appears that the specification cylinders in question require “strong outer packaging” just as the DOT-\nSP 7945 and DOT-SP 8495 cylinders do. Our questions are as follows:\n1) 2) 3) 4) 5) If a specification cylinder IS REQUIRED to ship gases but offered under a DOT SP instead, does\nthat change the requirement for use of an Overpack? The plain language of 49 CFR 173.25(a)(4)\nstates Overpacks are used when specification cylinders are “required.” Gasses are always\n“required” to be in specification cylinders IAW 49 CFR 173.301(a)(1). Therefore, are Overpacks\nalso always “required,” even for Special Permit cylinders?\nIf a Special Permit cylinder does not require Overpack based on the language of the SP for “a\nstrong outer packaging” (see Letter of Interpretation Reference No. 24-0010 answer A4), why\nare specification cylinders offered without the SP, which require “strong non-bulk outer\npackagings,” treated differently? Isn’t the DOT-SP marking also required and not visible just as\nthe DOT specification marking for a specification cylinder? See SP 7945 paragraph 7b and SP\n8495 paragraph 7a (marking) which describes marking requirements IAW 49CFR 178.35 and\n178.47 for these cylinders.\n49 CFR 173.301(a)(9) is referenced in the Special Permit and applicable to the specification\ncylinders in question. Therefore, the same requirement for a combination package exists and\nthe outer container is required in addition to the inner package. Is that correct?\nBased on the definition of Overpack in 49 CFR 171.8, if an item cannot be shipped as a single\npackage wouldn’t the outer box be part of the combination package and not an Overpack? In\nthis case, 3HT, 4DA, and 4DS cylinders containing gasses must always be placed in “strong outer\npackagings.” Therefore, these combination packages do not require an Overpack unless the\nouter packaging is “placed or stacked onto a load board such as a pallet and secured by\nstrapping, shrink wrapping, stretch wrapping, or other suitable means or placed in a protective\nouter packaging such as a box or crate.” Is that correct?\n49 CFR 173.301(a)(9) states “the outside of the combination packaging must be marked with an\nindication that the inner packagings conform to the prescribed specifications.” Does the word\n“OVERPACK” on a box containing gasses IAW 173.301(a)(9) (i.e. gasses in specification cylinders\nrequiring a combination package), for which 49 CFR 173.25(a) applies (i.e. an Overpack), qualify\nas “an indication that the inner packagings conform to the prescribed specifications”? In other\n\n<<>>\n\n6) 7) 8) 9) words, can the marking “OVERPACK” replace the marking “inner packagings conform to the\nprescribed specifications” in this case?\nIf the combination package described in question 5 does not comply with 49 CFR 173.25(a) (i.e.\nis not an Overpack), is the marking “inner packagings conform to the prescribed specifications”\nrequired to be on the outer container for Special Permit cylinders, just specification cylinders,\nneither, or both?\nIn regard to question 5, does each outer packaging conforming to 49 CFR 173.301(a)(9) (e.g. 3HT\ncylinder packed in a fiberboard box) also require the marking “inner packagings conform to the\nprescribed specifications,” in addition to the “OVERPACK” marking?\nThe articles in question are aircraft fire extinguishers which contain non-flammable gas. They do\nnot have non-flammable gas labels or markings with the proper shipping name (as would be\nfound on an industrial gas cylinder, for example). These labels/markings cannot be placed on the\ncylinders because the cylinders are a component of a 14CFR approved aircraft part. As such, no\nadditional labels may be placed on the articles and no FAA approved labels exist with the hazard\nlabel or proper shipping name marking. If the inner packagings DO NOT conform to the\nprescribed specifications (Ex: the proper shipping name marking and non-flammable gas label\nare not present on the inner cylinder in the combination package), is it still an Overpack?\nFor the scenario in question 8, it would also be inappropriate to mark the outer package “inner\npackagings conform to the prescribed specifications,” correct?\nWe appreciate your time and patience with this request and believe that the answers you provide will\nensure clarification and compliance with all aircraft repair stations, owners, operators, and distributors\nthat wish to comply fully with the HMR.\nBest Regards\nBrian Tyminski\nTym’s LLC\n\n<<>>\n\nU.S. Department\nof Transportation\nPipeline and Hazardous\nMaterials Safety\nAdministration\n1200 New Jersey Avenue, SE\nWashington, DC 20590\nMay 10, 2024\nMr. Patrick Schoenhoff\nGeneral Manager\nAMETEK AMERON\n10271 Bach Boulevard\nSaint Louis, MO 63132\nReference No. 24-0010\nDear Mr. Schoenhoff:\nThis letter is in response to your February 20, 2024, letter requesting clarification of the\nHazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to the overpack\nmarking requirements in § 173.25 as they relate to cylinders.\nWe have paraphrased and answered your questions as follows:\nQ1. You present a scenario where oxygen is shipped in Department of Transportation (DOT)\n3AA or 3HT specification cylinders, placed in a fiberboard box, and marked “UN1072,\nOxygen, Compressed.” You ask whether the fiberboard box must be marked\n“OVERPACK” as described in § 173.25(a)(4).\nA1. The answer is yes, provided the configuration meets the definition of an overpack, as\ndefined in § 171.8, and the specification markings on the cylinders are not visible through\nthe overpack. As prescribed in § 173.25(a)(4), the word “OVERPACK” is required to be\nmarked on an overpack if package specification markings—when required—are not\nvisible.\nQ2. In connection to question Q1, you ask whether it is a violation of the HMR to mark a\nfiberboard box with “OVERPACK” if it does not meet the definition of an overpack as\ndefined in § 171.8.\nA2. The answer is yes. Marking a fiberboard box with “OVERPACK” is a violation of the\nHMR if it does not meet the definition of an overpack as defined in § 171.8.\n\n<<>>\n\nQ3. You present a scenario where fire extinguishers are shipped under DOT Special Permits\n(SPs)—DOT SP-7945,\n1 DOT SP-8495,\n2 and DOT SP-127263\n—and marked “UN1044,\nFire Extinguishers.” You ask whether the “OVERPACK” mark is required on the\nfiberboard box containing fire extinguisher cylinders shipped under DOT SP-7945,\nDOT SP-8495, and DOT SP-12726.\nA3. Except when transported in DOT specification cylinders (see DOT-SP 12726 paragraph\n7.a), the answer is no. The SPs referenced in your letter—DOT SP-7945 and\nDOT SP-8495—state: “non-DOT specification cylinder conforming with all regulations\napplicable to a DOT specification 4DS cylinder.\n” Though specification 4DS cylinders do\nrequire the “OVERPACK” marking when enclosed in a fiberboard box, in accordance\nwith § 173.25(a)(4), the overpack marking is not required for DOT-SP 7945 and\nDOT-SP 8495, since the cylinders in question are not considered to be DOT specification\ncylinders (please also see answer A4). As such, the “OVERPACK” marking is also not\nrequired under DOT SP-12726, when non-DOT specification cylinders are used as\nspecified in paragraph 7.a.\nQ4. In connection to question Q3, you ask whether it is a violation of the HMR to mark a\nfiberboard box with “OVERPACK” if it does not meet the definition of an overpack as\ndefined in § 171.8.\nA4. See answer A2. However, when the SP requires the use of a strong outer packaging—as\nin DOT-SP 7945 paragraph 8.g. or DOT-SP 8495 paragraph 8.g.—the outer packaging\ndoes not meet the definition of an overpack, and therefore, “OVERPACK” is not an\nappropriate marking.\nAlso note, DOT-SP 12726 paragraph 7.a. authorizes the use of both non-DOT\nspecification cylinders and DOT specification cylinders, and—when DOT specification\ncylinders are used—the “OVERPACK” marking is required unless the markings\nrepresentative of each package type contained in the overpack are visible from outside of\nthe overpack.\nI hope this information is helpful. Please contact us if we can be of further assistance.\nSincerely,\nSteven Andrews\nActing Chief, Regulatory Review and Reinvention Branch\nStandards and Rulemaking Division\n1 https://www.phmsa.dot.gov/hazmat/documents/offer/SP7945.pdf/2022024177/SP7945\n2 https://www.phmsa.dot.gov/hazmat/documents/offer/SP8495.pdf/2021114098/SP8495\n3 https://www.phmsa.dot.gov/hazmat/documents/offer/SP12726.pdf/2020064323/SP12726\n\n<<>>\n\nPollack\nFrom: INFOCNTR (PHMSA)\nTo: Dodd, Alice (PHMSA)\nCc: Hazmat Interps\nSubject: FW: Overpack Interpretation Request\nDate: Friday, February 23, 2024 2:13:21 PM\nAttachments: image001.png\nimage002.png\nimage003.png\nOverpack Clarification Request.pdf\n24-0010\nHi Alice,\nPlease see the attached interpretation request. Let us know if you need anything.\nSincerely,\nJanaye\nFrom: Patrick Schoenhoff \nSent: Tuesday, February 20, 2024 2:23 PM\nTo: PHMSA HM InfoCenter \nSubject: Overpack Interpretation Request\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.\nHello,\nPlease see the attached request for Interpretation of the use of Overpack labels on packages\ncontaining charged cylinders.\nFeel free to contact me with any questions you have with this request.\nBest regards,\nPatrick Schoenhoff\nTechnical Director / General Manager\nD: +1 314 428 2062 x1077 | 10271 Bach Boulevard\nSaint Louis, MO 63132\nwww.ameronglobal.com\nO: +1 314 428 2062 | E: patrick.schoenhoff@ametek.com\n\n<<>>\n\nThis email, and any files transmitted with it, are confidential and intended solely for the use of the individual or entity to whom they are\naddressed. If you have received this email in error, please notify the sender and delete this email. If you are not the intended recipient,\nyou are notified that disclosing, copying, distributing, or taking any action in reliance on the contents of this information, is strictly\nprohibited.\n\n<<>>\n\nAMERON\n10271 BACH BOULEVARD\nSAINT LOUIS. MO 63132\n314-428-2062 PH\nFebruary 20, 2024\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\nMr. Kelley,\nI am requesting a Letter of Interpretation for the Overpack labeling of packages in\nthe following scenarios.\nScenario 1: An Oxygen Cylinder with a DOT rating of either 3AA or 3HT is packaged\nin a fiberboard box. The box is marked with UN1072 Oxygen, Compressed labels.\nQuestion 1: Does the above packaging constitute being labeled as an “Overpack”?\nQuestion 2: If not meeting the definition or requirement of an “Overpack”, is marking\nthe box as an Overpack a violation of the regulations?\nScenario 2: A Fire Extinguisher Cylinder with a DOT SP rating of SP-8495 or SP-\n7945 is packaged in a fiberboard box. The box is marked with UN1044, Fire\nExtinguishers SP-12726 labels and then shipped per SP-12726 (of which we hold\nParty Status).\nQuestion 3: Does the above packaging constitute being labeled as an “Overpack”\nwith an SP cylinder?\nQuestion 4: If not meeting the definition or requirement of an “Overpack”, is marking\nthe box as an Overpack a violation of the regulations?\nThank you for your help on this matter, and feel free to contact me if you have any\nquestions regarding these scenarios.\nBest Regards,\nPatrick Schoenhoff\nGeneral Manager\nAMETEK AMERON\n10271 Bach Boulevard\nSaint Louis, MO 63132\n314-428-2062 X1077\nE-mail: patrick.schoenhoff@ametek.com","truncated":false,"body_characters":23693}