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Letters of Interpretation

PHMSA has published several Frequently Asked Questions (FAQs) documents on programmatic topics. Please review these documents here at: https://www.phmsa.dot.gov/about-phmsa/phmsa-faqs.

Additionally, Office of Hazardous Materials Safety has published Hazardous Materials FAQs based on letters of interpretation on the following topics:

Office of Hazardous Materials Safety: For questions about transporting hazardous materials, needing clarifications of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180), or requesting a formal letter of interpretation, please go to the Hazardous Materials Information Center (HMIC) page for contact information (phone and email address). Pending interpretation letters that are under review by the Office of Hazardous Materials Safety can be found at Pending Hazardous Materials (Hazmat) Interpretations.  

Office of Pipeline Safety: 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: pipeline_interp_submittal@dot.gov. 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.

Interpretation letters under review are available at the Office of Pipeline Safety’s Interpretation Review page. To submit comments on an interpretation under review, proceed to the Interpretation Review page, locate the interpretation to comment on, and click the appropriate link to submit a comment on the corresponding interpretation. Comment submissions will be accepted for 30-days after the interpretation letter is posted.

This section of the website below provides the ability to find regulations information including regulations parts, content of sections, and interpretations for regulations sections. A list of parts, identified by the part number and subject is also provided. 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.

The eCFR is also searchable by keyword and other available options on the eCFR website. To search and browse regulations using the eCFR website, use the link below. For assistance, please send an email to PHMSA.Webmaster@dot.gov.

Search the eCFR

Interpretations Reference #

Search Tip: Use quotation marks to search for commonly used phrases, such as “gas transmission” or “cargo tank motor vehicle.”
E.g., 02/09/2021
E.g., 02/09/2021
Ref ID: Date Company Name Individual Name Response Document
PI-99-0106 Colonial Pipeline Company Mr. Stephen E. Gilliam View
99-0320 U.S. Marine Corps Air Station Mr. Dan Kesall View
99-0124 Arent Fox Kintner Plotkin Kahn, PLLC Mr. Paul Jackson Rice View
99-0269 Poitevent Carrère & Denègre L.L.P. Mr. Stanley A. Millan View
99-0280 Challenger Transportation, Inc. Mr. Jeff K. Ehrman View
99-0246 Quintiles Simirex Mr. Christopher Swift View
99-0306 California Highway Patrol< Mr. George Barber View
99-0059 Illinois Department of Transportation Mr. Terrence J. Moore View
PI-99-0105 City of Rolling Meadows Mr. Rodney A. Blane View
99-0162 Carib Ex Worldwide Ms. Juanita Caban View
99-0143 Chem-Nuclear Systems Kevin M. Lee View
99-0277 Thunderbird Cylinder, Inc. Mr. Fred A. Nachman View
99-0217 LaRoche Industries Inc. Mr. Carlton W. Hendrix View
99-0176 Kagan Aerospace Corporation Mr. Gregory Maynard View
99-0297 Neiman Marcus Direct Mr. Frank Ramirez View
99-0278 Condon & Forsyth, LLP Mr. David F. Rifkind View
PI-99-0104 Illinois Power Company Ms. Amy L. Hammond View
99-0235 Modern Safety Techniques Mr. Charles F. Martin, P.E. View
99-0258 Express Transport by Air Inc. Ms. Angela Flynn View
99-0065 Sacramento Blood Center Ms. Catherine J. Feiock View
99-0172 Radian International Mr. Andrew N. Romach View
99-0204 Baker Hughes Ms. Shelley A. Espinoza View
99-0264 Riviana Foods Inc. Mr. Lejo C. Brana, CPP View
99-0239 Howrey & Simon, Attorneys at Law Mr. George Kerchner View
99-0260 Oklahoma LP Gas Administration Mr. Gary McDonald View
99-0019 Western Poly Drums, Inc Mr. Floyd A. Whitney View
99-0231 Bayer Business Group Diagnostics Ms. Sonia Christensen Stewart View
99-0034 Quality Gas Products Mr. Chuck Wilson View
99-0139 Consumers Energy/LCS Mr. Manny Tuazon View
99-0220 Storage Technology Corp. Mr. Jerry Beasley View
99-0094 Chemtech Products, Inc. Mr. James R. Winkler View
99-0177 DELTA Analytical Corporation Mr. Jeff Jones View
99-0146 International Business Machines (IBM) Mr. Richard Eggleston View
99-0197 Mr. Raymond K. Barwin View
99-0244 Corporate Environmental Advisors, Inc. Mr. Frank B. Postma, P.G. View
99-0202 The Boeing Company Ms. Michele A. Giusiana View
99-0225 HAZMATEAM, INC. Mr. Leo Traverse View
PI-99-0103 Chief, Gas Pipeline Safety Division Mr. Glynn Blanton View
99-0090 Greif Bros. Corporation Mr. Joseph J. Grebe View
99-0152 Steptoe &; Johnson, LLP Mr. David H. Coburn View
99-0175 Mr. C. Vleugels View
99-0186 International Carbon Black Association Mr. Jimmy W. Boyd View
99-0169 Ultramar Diamond Shamrock Mr. George Lewis View
99-0117 Lockheed Martin Missiles Mr. Michael D. Brewster View
99-0232 Argonne National Laboratory Mr. Rudolph Bouie View
99-0198 HB Fuller Company Mr. Eugene J. Secor View
99-0205 R & L Transfer, Inc. Mr. Randy Russell View
99-0215 Mr. Chris Brown View
99-0165 Toyota Motor Manufacturing, Kentucky, Inc Ms. Delinda. Arnold View
99-0219 Uniroyal Chemical Company, Inc. Mr. Donald Hodder View