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Section §173.21: Forbidden materials and packages

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.

PHMSA has published several Frequently Asked Questions (FAQ) documents on regulatory topics. Please review our FAQ documents below:

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 section 173.21 on the ECFR website

Interpretation Responses

Ref ID Date Company Name Individual Name Response Document
18-0110 Ascent Resources Utica, LLC Steven Parrish View
18-0046 Hawks Logistics Steve Hawks View
18-0043 Ventura County District Attorney's Office Mitchel Disney View
15-0163 MPS Group Ms. Cynthia Walczak View
07-0037 Horizon Lines Mr. Cliff Bartley  View
02-0223 Hamburg-Sued, Aliamca and Crowley Dawn M. Abbaticchio View
99-0173 Shao Chen Mr. Mike He View
08-0216 Hawkins, Inc. Mr. Chris W. Gibson View
10-0233 Veolia ES Technical Solutions, L.L.C Ms. Jennifer Eberle View
13-0111 Baker Hughes Mr. Aubrey R. Campbell View
05-0156 CheckPoint Mailers Incorporated Ms. Sherry Anderson View
10-0244 Ashland, Inc. Mr. Gregory S. Phillips View
13-0186 UTi Ms. Kathryn Singer View
12-0131 New Century Transportation, Inc. Ms. Donna Horn View
09-0300 Sartorius Stedim Filters, Inc. Mr. José H. Braulio-Martinez View
98-0509 Wood Kote Products, Inc Mr. Gary P. Velikanje View
16-0080 Technology Solutions Mr. William Weddle View
99-0255 Onyx Environmental Services L.L.C. Ms. Lauren Malone View
98-0510 HMT Associates, L.L.C. Mr. Gordon Rousseau View
15-0149 Tailgate In A Box Mr. Matthew MacLean View
99-0288 Intech Services, Inc. Ms. Anne E. Johnson View
99-0230 CleanHarbors Environmental Services, Inc. Mr. Peter W. Egan View
09-0307 Lovitz PSC Environmental Services, LLC Mr. James V. Lovitz View
02-0316 CNDT, Inc. Ron Petty View
14-0073 United States Postal Service Ms. Joan Hall View
07-0152 ZPower, Inc. Mr. Ross E. Dueber, Ph.D View
09-0084 Syncro Medical Innovations, Inc. Mr. Lalit Sabramanian View
14-0025 Veolia ES Technical Solutions, L.L.C. Ms. Jennifer Eberle View
CHI-05-001 Gebauer Company Daniel J. Van Kuren View
08-0035 BD Medical - Medical Surgical Systems Mr. Lane Arbittier View
11-0282 Ms. Kathy S. Gentry View
09-0160 National Electrical Manufacturers Association Mr. Kyle Pitsor View
08-0229 DeVibiss Healthcare Mr. David Greene View
15-0040 Wiley Rein LLP Mr. George Kerchner View
08-0249 Stericycle, Inc. Mr. Dan Fadgen View
08-0019 Mr. Charles W. Guthrie View
06-0027 Mr. Steve Kranyec View
09-0144 Cytec Industries Stamford Hazards Lab Mr. Mark Ryan View
09-0155 Inogen, Inc. Mr. Matt Scribner View
12-0006 Lighter Association, Inc. Mr. David H. Baker View
09-0219 Mr. Ronald B. Johnstone View
10-0153 Public Health, Seattle and King County Mr. William Perry View
10-0028 Total Reclaim, Inc. Ms. Peggy Halferty View
11-0054 Environmental Management Ms. Misha Gonzales View
14-0188 Alaska Air, SEADG Mr. Ron Fink View
03-0301 National Cargo Bureau, Inc. Captain Sam Rogers View
04-0033 PPG Industries, Inc. Mr. Gordon W. Rousseau View