Classes, precedence, & PG

Scope

The HMR requires that anyone offering a hazardous material for shipment must identify and classify their material.

Regulatory citations

• 49 CFR 171.8 — General—Definitions and abbreviations
• 49 CFR 173.50 — Class 1—Definitions
• 49 CFR 173.115 — Class 2, Divisions 2.1, 2.2, and 2.3—Definitions
• 49 CFR 173.120 — Class 3—Definitions
• 49 CFR 173.124 — Class 4, Divisions 4.1, 4.2 and 4.3—Definitions
• 49 CFR 173.127 — Class 5, Division 5.1—Definition and assignment of packing groups
• 49 CFR 173.128 — Class 5, Division 5.2—Definitions and types
• 49 CFR 173.132 — Class 6, Division 6.1—Definitions
• 49 CFR 173.134 — Class 6, Division 6.2—Definitions and exceptions
• 49 CFR 173.136 — Class 8—Definitions
• 49 CFR 173.140 — Class 9—Definitions
• 49 CFR 173.403 — Class 7 (radioactive) materials—Definitions

Key definitions

• Elevated temperature material: A material in a bulk package that is:
  • In a liquid phase at a temperature at or above 212°F (100°C), or
  • In a liquid phase with a flash point at or above 100°F (37.8°C) that is intentionally heated above its flash point, or
  • In a solid phase and at a temperature at or above 464°F (240°C).
• Hazardous substance: A material listed in Appendix A to 172.101 and in a quantity in one package that meets or exceeds the reportable quantity (RQ).
• Hazardous waste: A material subject to the waste manifest requirements of the Environmental Protection Agency as specified in 40 CFR 262.
• Marine pollutant: A material listed in Appendix B to 172.101 and is packaged in a concentration which equals or exceeds 10% for marine pollutants and 1% for severe marine pollutants. Marine pollutants are always regulated by vessel. They are only regulated by air, rail, or highway when in bulk packagings.

Summary of requirements

• All hazardous materials must fall into one of the hazard classes listed in the Hazardous Materials Regulations (HMR).
• Some hazard classes are further broken down into divisions.
• Packing Groups indicate the degree of danger that may be presented within hazardous materials.