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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
173.5 Agricultural operations
173.50 Class 1-Definitions
173.52 Classification codes and compatibility groups of explosives
173.54 Forbidden explosives
173.56 New explosives-definition and procedures for classification and approval
173.58 Assignment of class and division for new explosives
173.59 Description of terms for explosives
173.5a Oilfield service vehicles, mechanical displacement meter provers, and roadway striping vehicles exceptions
173.6 Materials of trade exceptions
173.60 General packaging requirements for explosives
173.61 Mixed packaging requirements
173.62 Specific packaging requirements for explosives
173.63 Packaging exceptions
173.64 Exceptions for Division 1.3 and 1.4 fireworks
173.65 Exceptions for Division 1.4G consumer fireworks
173.66 Requirements for bulk packagings of certain explosives and oxidizers
173.7 Government operations and materials
173.8 Exceptions for non-specification packagings used in intrastate transportation
173.9 Transport vehicles or freight containers containing lading which has been fumigated
174.1 Purpose and scope
174.101 Loading Class 1 (explosive) materials
174.104 Division 1.1 or 1.2 (explosive) materials; car selection, preparation, inspection, and certification
174.14 Movements to be expedited
174.204 Tank car delivery of gases, including cryogenic liquids
174.24 Shipping papers
174.26 Notice to train crews
174.304 Class 3 (flammable liquid) materials in tank cars
174.31 Requirements for the operation of high-hazard flammable trains
174.55 General requirements
174.57 Cleaning cars
174.63 Portable tanks, IM portable tanks, IBCs, Large Packagings, cargo tanks, and multi-unit tank car tanks
174.67 Tank car unloading
174.750 Incidents involving leakage
174.81 Segregation of hazardous materials
174.85 Position in train of placarded cars, transport vehicles, freight containers, and bulk packagings
174.9 Safety and security inspection and acceptance
175.1 Purpose, scope and applicability
175.10 Exceptions for passengers, crewmembers, and air operators
175.10 Exceptions for passengers, crewmembers, and air operators
175.25 Passenger notification system
175.26 Notification at cargo facilities of hazardous materials requirements
175.30 Inspecting shipments
175.31 Reports of discrepancies
175.33 Shipping paper and notification of pilot-in-command
175.501 Special requirements for oxidizers and compressed oxygen
175.700 Special limitations and requirements for Class 7 materials
175.705 Radioactive contamination
175.75 Quantity limitations and cargo location
175.78 Stowage compatibility of cargo