How to Use the HMR

The Codes of Federal Regulations are structured by title, subtitle, chapter, subchapter, and parts. The structure of the HMR is as follows:

• Title: Title 49 - Transportation
• Subtitle: Subtitle B - Other Regulations Relating to Transportation
• Chapter: Chapter I - Pipeline and Hazardous Materials Safety Administration, Department of Transportation
• Subchapter: Subchapter C - Hazardous Materials Regulations
• Parts: Parts 171-185
  • Part 171: General Information, Regulations, and Definitions
  • Part 172: Hazardous Materials Table, Special Provisions, Hazardous Materials Communications, Emergency Response Information, Training Requirements, and Security Plans
  • Part 173: Shippers - General Requirements for Shipments and Packagings
  • Part 174: Carriage by Rail
  • Part 175: Carriage by Aircraft
  • Part 176: Carriage by Vessel
  • Part 177: Carriage by Public Highway
  • Part 178: Specifications for Packagings
  • Part 179: Specifications for Tank Cars
  • Part 180: Continuing Qualification and Maintenance of Packagings
  • Parts 181-185: Reserved for future use

The Parts of the HMR can be grouped into four general areas:

1. Identification and Classification (Parts 171 and 173)
2. Hazard Communication (Part 172, Subparts A-G)
3. Packaging Requirements (Parts 173, 178, 179, and 180)
4. Operational Rules (Parts 171, 173, 174, 175, 176, and 177)

Each Part of the HMR is divided into sections, paragraphs, subparagraphs, and sub-subparagraphs. For example, the provision that states that large quantities of hazardous materials packed in non-bulk packages are required to be marked with the proper shipping name and identification number can be found in Section 172.301, Paragraph (a), Subparagraph (3), Sub-subparagraph (i).

References to the HMR are always given by the CFR reference number, such as 172.301(a)(3)(i), because page numbers change often due to revisions, additions, and deletions. In this course, sections are denoted with the section symbol (such as §172.301).

The following rules of construction provide a key to understanding the content in the HMR:

• Singular words include the plural and plural words include the singular, such as "hazardous materials" or "hazardous material"
• Masculine words include the feminine, such as "airmen"
• "Must" and "shall" mean required
• "Should" means recommended but not required
• "May" means permitted but not required
• "Includes" means includes, but not limited to
• "No person may" means no person is required, authorized, or permitted to

To learn more about DOT HAZMAT Awareness visit our DOT HAZMAT General Awareness Online Training web page.