Hazardous materials are classified into DOT packing groups based on their level of danger during transportation. The following guidelines provide details on how hazardous materials must be packaged for mailing through the Postal Service.
Hazardous materials in Classes 3, 4, 5, Division 6.1, Class 8, and certain hazardous materials in Class 9 are assigned to a DOT packing group.
The packing group assigned to a hazardous material is listed in column 5 of the Hazardous Material Table in 49 CFR § 172.101 and in column (d) of Appendix A.
Packing group designators are always written in Roman numerals. DOT packing groups are categorized as follows:
- Packing Group I: Great danger.
- Packing Group II: Medium danger.
- Packing Group III: Minor danger.
The packaging for mailable hazardous materials must comply with the appropriate instructions found in Appendix C. The correct Packaging Instruction for each hazardous material can be determined using Appendix A.
Mailers may not package or combine hazardous materials assigned to different hazard classes within a single mailpiece unless permitted by Postal Service standards.
USPS-produced Priority Mail Express and Priority Mail packaging supplies may not be used for shipping mailable hazardous materials. Refer to DMM 601.6.1.
Except as otherwise specified, rigid outer packaging must be used for shipments containing hazardous materials. Outer packaging, as defined in Appendix D, is the outermost enclosure that holds the primary receptacle, and if applicable, secondary packaging, which is absorbent and/or cushioning material.
When shipping hazardous materials, the following outer packaging is required:
- Weight Limits (\u2264 20 lbs.): Mailpieces containing hazardous materials weighing 20 pounds or less (except for item c.), must use outer packaging rated at 200 lb. burst test or 32-edge crush test strength or equivalent, at minimum.
- Weight Limits (\u2265 20 lbs.): Mailpieces containing hazardous materials weighing more than 20 pounds (except for item c.), must use outer packaging rated at 275 lb. burst test or 44-edge crush test strength or equivalent, at minimum.
- Installed in Equipment or Device: Lithium batteries installed in the equipment or device they operate that are permitted to be mailed under 349 and 622 may utilize padded or poly bags as outer packaging, provided they are within a secondary packaging (i.e., original manufacturer‘s box) that can withstand a 1.2-meter drop test before being placed inside the padded or poly bag. These items must meet the following requirements:
- The equipment/device must be new, or manufacturer refurbished.
- The lithium batteries are afforded adequate protection by the equipment/device.
- The outer packaging does not display, and is not required to display, hazardous text, markings, or labels as permitted in 349.221(d) and 622.5(g).
Note: USPS-Produced Priority Mail Express and Priority Mail packaging must not be utilized for shipping mailable hazardous materials. Refer to 339.3 and DMM 601.6.1.
