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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
98-0418 Air Products and Chemicals, Inc. Mr. Richard J. Lloyd View
98-0421 Boe Gases Mr. John N. Thompson View
PI-98-002 James S. Stites View
98-0553 Mr. Kent Blair View
98-0083 USA Services, Inc. Mr. George Plum View
98-0509 Wood Kote Products, Inc Mr. Gary P. Velikanje View
98-0602 G.H. Johnson & Associates, Inc. Mr. James A. Noone View
98-0562 Mr. Kent Blair View
98-0551 Worthington Cylinder Corporation Mr. Steven T. Gentry View
98-0398 H.B. Fuller Automotive Company Mr. Gene Secor View
CHI-98-002 Southern California Edison Mr. Manuel Zamorano View
98-0402 LAX Civil Aviation Security Mr. Frank L. Webb View
98-0502 Department of the Army Ms. Marcia C. Davies, Ph.D View
98-0577 National Tank Truck Carriers, Inc. Mr. John L. Conley View
98-0579 National Tank Truck Carriers, Inc. Mr. John L. Conley View
98-0582 National Tank Truck Carriers, Inc. Mr. John L. Conley View
98-0548 Ross Trucking Co., Inc. Ms. Nancy McKnight View
98-0559 Kold Ban Internal, Ltd. Mr. James O. Burke View
98-0019 Allantoic Systems Mr. Lee R. Zwiefelhofer View
98-0404 Cleanlites Recycling, Inc. Ms. Jeanne Hourani View
98-0393 Allantoic Systems Mr. Lee R. Zwiefelhofer View
98-0414 Hazmateam, Inc. Mr. Leo Traverse View
98-0512 Waste Management, Inc. Mr. Daniel L. Duncan View
98-0530 Roger L. Goodman, D.D.S., P.C. View
PI-98-001 Tennessee Regulatory Authority Glynn Blanton View
98-0519 The Defense Contract Management Command Ms. Jill E. Pettibone View
98-0600 Regulatory Compliance Services Mr. R. J. Reynolds View
98-0504 Minnesota Department of Transportation Mr. Michael Ritchie View
98-0587 Baltimore Cargo Tank Services, Inc. Mr. Roy N. Clark View
98-0591 Baltimore Cargo Tank Services, Inc. Mr. Roy N. Clark View
98-0528 Pacific Resource Recovery Mr. Bill Rosenthal View
98-0608 DuPont de Nemours &Co. Mr. Randolph Martin View
98-0560 Spectra Gases, Inc. Mr. William Miller View
98-0424 American Trucking Association Mr. Paul M. Bomgardner View
98-0422 BMD Enterprises, Inc. Ms. Marilynn Dunn View
98-0423 Mr. Patrick G. Kruger View
98-0500 H.B. Fuller Automotive Company Mr. Gene Secor View
98-0537 All-Pak, Inc. Mr. R. C. Watt View
98-0525 Elkem Metals Company Ms. Sharon L. Thompson View
98-0532 Delphi Energy & Engine Management Systems Mr. David McCullough View
98-0407 Big T Transfer Inc. Ms. Lisa Smith View
98-0415 ROMIC Environmental Technologies Corp. Mr. Kurt Swart View
98-0405 ASi International Mr. Greg Lemley View
98-0529 Pall Corporation Ms. Susan Morrissey View
98-0539 Hercules Incorporated Mr. L. L. Kerstetter View
98-0524 Hunt Shipmate, Inc. Mr. Steven Charles View
98-0401 Shipmate, Inc. Mr. Steven Charles Hunt View
98-0511 Environmental, Health & Safety Mr. Joseph W. Gentile View
98-0558 Manchester Tank & Equipment Company Mr. Randy Wahl View
98-0584 Amerex Corporation Mr. Fred B. Goodnight View