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49 CFR Parts 100-199

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

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 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

Search the eCFR

E.g., 02/09/2021
E.g., 02/09/2021
Part/Section Subject
173.125 Class 4-Assignment of packing group
173.127 Class 5, Division 5.1-Definition and assignment of packing groups
173.128 Class 5, Division 5.2-Definitions and types
173.13 Exceptions for Class 3, Divisions 4.1, 4.2, 4.3, 5.1, 6.1, and Classes 8 and 9 materials
173.132 Class 6, Division 6.1-Definitions
173.133 Assignment of packing group and hazard zones for Division 6.1 materials
173.134 Class 6, Division 6.2-Definitions and exceptions
173.136 Class 8-Definitions
173.137 Class 8-Assignment of packing group
173.140 Class 9-Definitions
173.141 Class 9-Assignment of packing group
173.144 Other Regulated Material (ORM)-Definitions
173.150 Exceptions for Class 3 (flammable and combustible liquids)
173.150 Exceptions for Class 3 (flammable and combustible liquids)
173.151 Exceptions for Class 4
173.152 Exceptions for Division 5.1 (oxidizers) and Division 5.2 (organic peroxides)
173.153 Exceptions for Division 6.1 (poisonous materials)
173.154 Exceptions for Class 8 (corrosive materials)
173.155 Exceptions for Class 9 (miscellaneous hazardous materials)
173.156 Exceptions for limited quantity and ORM
173.157 Reverse logistics-General requirements and exceptions for reverse logistics
173.158 Nitric acid
173.159 Batteries, wet
173.159a Exceptions for non-spillable batteries
173.164 Mercury (metallic and articles containing mercury)
173.166 Safety devices
173.167 Consumer commodities
173.168 Chemical oxygen generators
173.170 Black powder for small arms
173.171 Smokeless powder for small arms
173.173 Paint, paint-related material, adhesives, ink and resins.
173.176 Capacitors
173.181 Pyrophoric materials (liquids)
173.183 Nitrocellulose base film
173.184 Highway or rail fusee
173.185 Lithium cells and batteries
173.185 Lithium cells and batteries
173.186 Matches
173.187 Pyrophoric solids, metals or alloys, n.o.s
173.188 White or yellow phosphorus
173.189 Batteries containing sodium or cells containing sodium
173.196 Category A infectious substances
173.197 Regulated medical waste
173.199 Category B infectious substances
173.2 Hazardous materials classes and index to hazard class definitions
173.202 Non-bulk packagings for liquid hazardous materials in Packing Group II
173.203 Non-bulk packagings for liquid hazardous materials in Packing Group III
173.206 Packaging requirements for chlorosilanes
173.21 Forbidden materials and packages
173.211 Non-bulk packagings for solid hazardous materials in Packing Group I