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Below are the available interpretations and guidance for the given section. To return to the list of parts, use the Parts link above. If you do not see any guidance or interpretation information below, that means there is none available for the given part/section. Return to the search page to browse additional regulations sections.

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Additionally PHMSA has Hazardous Materials FAQs based on letters of interpretation on the following topics:

This section of the website provides the ability to find regulations information including regulations parts, content of sections, and interpretations for regulations sections. Below is a list of parts, identified by the part number and subject. To browse sections by part, click on the subject link below. You will be taken to the eCFR website to view sections for a part.

A written regulatory interpretation, response to a question, or an opinion concerning a pipeline safety issue may be obtained by submitting a written request to the Office of Pipeline Safety (PHP–30), PHMSA, U.S. Department of Transportation, 1200 New Jersey Avenue SE., Washington, DC 20590–0001 or at the email address: In addition to email address, the requestor must include his or her return address and should also include a daytime telephone number. Requests should be submitted at least 120 days before the time the requestor needs a response.

Note: electronic submission is provided as alternative to the 49 CFR Part 190.11(b) mail-in requirement.

The regulations text of the section can be found on the eCFR website. To view the regulations text, use the link below. For assistance, please send an email to

View part 178 on the ECFR website

Interpretation Responses

Ref ID Date Company Name Individual Name Response Document
22-0070 Scopelitis, Gavin, Light, Hanson & Feary, P.C. Mr. Timothy W. Wiseman View
21-0071 Air General, Inc. Charles A. White View
20-0076 Packgen Keith Russ View
20-0004 North American Automotive Hazmat Action Committee Wayne Shafer View
19-0021 Gayston Corporation David Schmitz View
17-0041 WNWN International Mr. Ed Krisiunas View

Regulation Sections

Section Subject
178.1 Purpose and scope
178.2 Applicability and responsibility
178.3 Marking of packagings
178.33 Specification 2P; inner nonrefillable metal receptacles
178.33-1 Compliance
178.33-2 Type and size
178.33-3 Inspection
178.33-4 Duties of inspector
178.33-5 Material
178.33-6 Manufacture
178.33-7 Wall thickness
178.33-8 Tests
178.33-9 Marking
178.33a Specification 2Q; inner nonrefillable metal receptacles
178.33a-1 Compliance
178.22a-2 Type and size
178.33a-3 Inspection
178.33a-4 Duties of inspector
178.33a-5 Material
178.33a-6 Manufacture
178.33a-7 Wall thickness
178.33a-8 Tests
178.33a-9 Marking
178.33b Specification 2S; inner nonrefillable plastic receptacles
178.33b-1 Compliance
178.33b-2 Type and size
178.33b-3 Inspection
178.33b-4 Duties of inspector
178.33b-5 Material
178.33b-6 Manufacture
178.33b-7 Design qualification test
178.33b-8 Production tests
178.33b-9 Marking
178.33c Specification 2P; inner nonrefillable metal receptacle variation
178.33c-1 Compliance
178.33c-2 Variation
178.33d Specification 2Q; inner nonrefillable metal receptacle variations
178.33d-1 Compliance
178.33d-2 Variation 1
178.33d-3 Variation 2
178.35 General requirements for specification cylinders
178.36 Specification 3A and 3AX seamless steel cylinders
178.37 Specification 3AA and 3AAX seamless steel cylinders
178.38 Specification 3B seamless steel cylinders
178.39 Specification 3BN seamless nickel cylinders
178.42 Specification 3E seamless steel cylinders
178.44 Specification 3HT seamless steel cylinders for aircraft use
178.45 Specification 3T seamless steel cylinder
178.46 Specification 3AL seamless aluminum cylinders
178.47 Specification 4DS welded stainless steel cylinders for aircraft use
178.50 Specification 4B welded or brazed steel cylinders
178.51 Specification 4BA welded or brazed steel cylinders
178.53 Specification 4D welded steel cylinders for aircraft use
178.55 Specification 4B240ET welded or brazed cylinders
178.56 Specification 4AA480 welded steel cylinders
178.57 Specification 4L welded insulated cylinders
178.59 Specification 8 steel cylinders with porous fillings for acetylene
178.60 Specification 8AL steel cylinders with porous fillings for acetylene
178.61 Specification 4BW welded steel cylinders with electric-arc welded longitudinal seam
178.65 Specification 39 non-reusable (non-refillable) cylinders
178.68 Specification 4E welded aluminum cylinders
178.69 Responsibilities and requirements for manufacturers of UN pressure receptacles
178.70 Approval of UN pressure receptacles
178.71 Specifications for UN pressure receptacles
178.74 Approval of MEGCs
178.75 Specifications for MEGCs
178.255 Specification 60; steel portable tanks
178.255-1 General requirements
178.255-2 Material
178.255-3 Expansion domes
178.255-4 Closures for manholes and domes
178.255-5 Bottom discharge outlets
178.255-6 Loading and unloading accessories
178.255-7 Protection of valves and accessories
178.255-8 Safety devices
178.255-9 Compartments
178.255-10 Lining
178.255-11 Tank mountings
178.255-12 Pressure test
178.255-13 Repair of tanks
178.255-14 Marking
178.255-15 Report
178.273 Approval of Specification UN portable tanks
178.274 Specifications for UN portable tanks
178.275 Specification for UN Portable Tanks intended for the transportation of liquid and solid hazardous materials
178.276 Requirements for the design, construction, inspection and testing of portable tanks intended for the transportation of non-refrigerated liquefied compressed gases
178.277 Requirements for the design, construction, inspection and testing of portable tanks intended for the transportation of refrigerated liquefied gases
178.318 Specification MC 201; container for detonators and percussion caps
178.318-1 Scope
178.318-2 Container
178.318-3 Marking
178.320 General requirements applicable to all DOT specification cargo tank motor vehicles
178.337 Specification MC 331; cargo tank motor vehicle primarily for transportation of compressed gases as defined in subpart G of part 173 of this subchapter
178.337-1 General requirements
178.337-2 Material
178.337-3 Structural integrity
178.337-4 Joints
178.337-5 Bulkheads, baffles and ring stiffeners
178.337-6 Closure for manhole
178.337-7 Overturn protection
178.337-8 Openings, inlets, and outlets
178.337-9 Pressure relief devices, piping, valves, hoses, and fittings
178.337-10 Accident damage protection
178.337-11 Accident damage protection
178.337-13 Supporting and anchoring
178.337-14 Gauging devices
178.337-15 Pumps and compressors
178.337-16 Testing
178.337-17 Marking
178.337-18 Certification
178.338 Specification MC-338; insulated cargo tank motor vehicle
178.338-1 General requirements
178.338-2 Material
178.338-3 Structural integrity
178.338-4 Joints
178.338-5 Stiffening rings
178.338-6 Manholes
178.338-7 Openings
178.338-8 Pressure relief devices, piping, valves, and fittings
178.338-9 Holding time
178.338-10 Accident damage protection
178.338-11 Discharge control devices
178.338-12 Shear section
178.338-13 Supporting and anchoring
178.338-14 Gauging devices
178.338-15 Cleanliness
178.338-16 Inspection and testing
178.338-17 Pumps and compressors
178.345 General design and construction requirements applicable to Specification DOT 406 (178.346), DOT 407 (178.347), and DOT 412 (178.348) cargo tank motor vehicles
178.345-1 General requirements
178.345-2 Material and material thickness
178.345-3 Structural integrity
178.345-4 Joints
178.345-5 Manhole assemblies
178.345-6 Supports and anchoring
178.345-7 Circumferential reinforcements
178.345-8 Accident damage protection
178.345-9 Pumps, piping, hoses and connections
178.345-10 Pressure relief
178.345-11 Tank outlets
178.345-12 Gauging devices
178.345-13 Pressure and leakage tests
178.345-14 Marking
178.345-15 Certification
178.346 Specification DOT 406; cargo tank motor vehicle
178.346-1 General requirements
178.346-2 Material and thickness of material
178.346-3 Pressure relief
178.346-4 Outlets
178.347 Specification DOT 407; cargo tank motor vehicle
178.347-1 General requirements
178.347-2 Material and thickness of material
178.347-3 Manhole assemblies
178.347-4 Pressure relief
178.347-5 Pressure and leakage test
178.348 Specification DOT 412; cargo tank motor vehicle
178.348-1 General requirements
178.348-2 Material and thickness of material
178.348-3 Pumps, piping, hoses and connections
178.348-4 Pressure relief
178.348-5 Pressure and leakage test
178.350 Specification 7A; general packaging, Type A.
178.500 Purpose, scope and definitions
178.502 Identification codes for packagings
178.503 Marking of packagings
178.504 Standards for steel drums
178.505 Standards for aluminum drums
178.506 Standards for metal drums other than steel or aluminum
178.507 Standards for plywood drums
178.508 Standards for fiber drums
178.509 Standards for plastic drums and jerricans
178.510 Standards for wooden barrels
178.511 Standards for aluminum and steel jerricans
178.512 Standards for steel, aluminum or other metal boxes
178.513 Standards for boxes of natural wood
178.514 Standards for plywood boxes
178.515 Standards for reconstituted wood boxes
178.516 Standards for fiberboard boxes
178.517 Standards for plastic boxes
178.518 Standards for woven plastic bags
178.519 Standards for plastic film bags
178.520 Standards for textile bags
178.521 Standards for paper bags
178.522 Standards for composite packagings with inner plastic receptacles
178.523 Standards for composite packagings with inner glass, porcelain, or stoneware receptacles
178.600 Purpose and scope
178.601 General requirements
178.602 Preparation of packagings and packages for testing
178.603 Drop test
178.604 Leakproofness test
178.605 Hydrostatic pressure test
178.606 Stacking test
178.607 Cooperage test for bung-type wooden barrels
178.608 Vibration standard
178.609 Test requirements for packagings for infectious substances
178.700 Purpose, scope and definitions
178.702 IBC codes
178.703 Marking of IBCs
178.704 General IBC standards
178.705 Standards for metal IBCs
178.706 Standards for rigid plastic IBCs
178.707 Standards for composite IBCs
178.708 Standards for fiberboard IBCs
178.709 Standards for wooden IBCs
178.710 Standards for flexible IBCs
178.800 Purpose and scope
178.801 General requirements
178.802 Preparation of fiberboard IBCs for testing
178.803 Testing and certification of IBCs
178.81 Drop test
178.811 Bottom lift test
178.812 Top lift test
178.813 Leakproofness test
178.814 Hydrostatic pressure test
178.815 Stacking test
178.816 Topple test
178.817 Righting test
178.818 Tear test
178.819 Vibration test
178.900 Purpose and scope
178.905 Large Packaging identification codes
178.910 Marking of Large Packagings
178.915 General Large Packaging standards
178.920 Standards for metal Large Packagings
178.925 Standards for rigid plastic Large Packagings
178.930 Standards for fiberboard Large Packagings
178.935 Standards for wooden Large Packagings
178.94 Standards for flexible Large Packagings
178.950 Purpose and scope.
178.955 General requirements
178.960 Preparation of Large Packagings for testing
178.965 Drop test
178.970 Bottom lift test
178.975 Top lift test
178.980 Stacking test
178.985 Vibration test
178.1000 Purpose and scope
178.1005 Flexible Bulk Container identification code
178.1010 Marking of Flexible Bulk Containers
178.1015 General Flexible Bulk Container standards
178.1020 Period of use for transportation of hazardous materials in Flexible Bulk Containers
178.1030 Purpose and scope
178.1035 General requirements
178.1040 Preparation of Flexible Bulk Containers for testing
178.1045 Drop test
178.1050 Top lift test
178.1055 Stacking test
178.1060 Topple test
178.1065 Righting test
178.1070 Tear test
178.810 Drop test