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Section §172.303: Prohibited marking

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 172.303 on the ECFR website

Interpretation Responses

Ref ID Date Company Name Individual Name Response Document
21-0098 Dominion Energy Mr. Tim Carter View
19-0089 Uniweld Products, Inc. Janet Beets View
15-0148 New Jersey State Police Lt. John V. Guzzo View
15-0010 Hexagon Ragasco North America Inc. Mr. Jonas Berglund View
14-0103 Von Briesen & Roper, S.C. Attorneys at Law Mr. Mark F. Foley View
13-0192 Nynas USA, Inc. Mr. Edward Skelton View
99-0220 Storage Technology Corp. Mr. Jerry Beasley View
12-0110 Akrochem Corporation Scott Fleming View
12-0146 ADG Compliance Manager Mr. Bob Cogen View
15-0026 Arkema Inc. Ms. Christina Kurtz View
09-0257 Benjamin Moore & Co. Mr. Prokopis Christou View
08-0088 Mr. Merle M. Schnackenberg View
02-0145 Hazmat Environmental Group, Inc Colleen A. Orth View
04-0252 C.L. Smith Company Mr. Lonnie Jaycox  View
11-0244 Arch Chemicals, Inc. Ms. Jennifer M. Daugherty View
06-0235 Railroad Commission of Texas Mr. James T. Osterhaus  View
04-0041 Western International Gas Ms. Kathy McKenzie View