For domestic mail sent via air transportation, a mailpiece containing a hazardous material must:
- Consist of a material that is permitted to be transported by air.
- Be prepared and packaged under all applicable conditions for transport by air.
- Be sent by Priority Mail Express, Priority Mail, First-Class Mail, or First-Class Package Service.
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, along with the mailing standards in DMM 601.10, provide full details of the conditions under which mailable hazardous materials may be sent in domestic mail via air transportation.