Publication 52, Hazardous, Restricted, and Perishable Mail > 7 Air Transportation Requirements > 72 Hazardous Materials: Air Transportation
For domestic mail sent via air transportation, a mailpiece containing a hazardous material must:
Hazardous materials are not acceptable for air transportation if they are not prepared in compliance with the specific applicable requirements. These requirements consider the degree of hazard, quantity of material, method of packaging, required shipping papers, and adequacy of labels and/or markings required for carriage aboard an aircraft.
Chapter 3 and the Packaging Instructions in Appendix C, provide full details of the conditions under which mailable hazardous materials may be sent in domestic mail via air transportation.