Publication 52 - Hazardous, Restricted, and Perishable Mail > Appendix C
These Postal Service packaging instructions are for mailable types of hazardous materials. The numeric digits 1 through 9 correspond to the appropriate hazard class. The alpha characters differentiate the separate groups of materials within a hazard class. Packaging instructions 10A through 10C provide packaging information relating to special provisions not associated with a specific hazard class. Postal Service packaging instructions are provided as follows:
Hazard Class 1: Explosives
Hazard Class 2: Gases
Hazard Class 3: Flammable and Combustible Liquids
Hazard Class 4: Flammable Solids
Hazard Class 5: Oxidizing Substances, Organic Peroxides
Hazard Class 6: Toxic Substances and Infectious Substances
Hazard Class 7: Radioactive Materials
Hazard Class 8: Corrosives
Hazard Class 9: Miscellaneous Hazardous Materials
Category 10: Other Packaging Instructions