An excepted quantity is a defined amount of a specific hazardous material, eligible for transport aboard passenger aircraft, which is not subject to any DOT requirements (e.g., packaging, marking, labeling, etc.) other than those in 49 CFR 173.4a. Very few hazardous materials can be shipped under the excepted quantity provision. Additionally, for Postal Service purposes, Class 1, Class 2, Class 4, Division 6.2, and Class 7 materials are not permitted to be sent as an excepted quantity. The excepted quantity provision is applicable to domestic mail only, and its use is prohibited for international shipments or APO/FPO/DPO mail. The excepted quantity provision can be used in domestic air or surface transportation (highway, rail, or vessel).
Only materials authorized for transport aboard passenger aircraft in accordance with 49 CFR 172.101 and appropriately classed within one of the following hazard classes or divisions may be mailed as an excepted quantity:
- Class 3, Packing Groups II and III;
- Division 5.1, Packing Groups II and III;
- Division 5.2 materials, only when contained in a chemical kit, first aid kit, or polyester resin kit;
- Division 6.1, Packing Group III only;
- Class 8, Packing Groups II and III only, except for UN2803, Gallium and UN2809, Mercury; and
- Class 9, except for UN1845, Carbon dioxide, solid, or Dry ice, and lithium batteries.
Materials identified in Appendix A as prohibited under column E, USPS Mailability, are ineligible for mailing under the excepted quantity provision without regard to their hazard class, division, or packing group.
The maximum quantity of hazardous materials in each inner (primary) packaging is limited to 30 g (1 ounce) or 30 ml (1 ounce) for solids or liquids. The maximum aggregate quantity of hazardous material in any mailpiece cannot exceed:
- For Packing Group II materials and Class 9 materials, 500 g (1.1 lbs.) for solids or 500 ml (.1 gallon) for liquids.
- For Packing Group III materials, 1 kg (2.2 lbs.) for solids or 1 liter (0.2 gallon) for liquids.
- For Division 5.2 materials, 500 g (1.1 lbs.) for solids or 500 ml (.1 gallon) for liquids.
Hazardous materials eligible to be shipped under the excepted quantity provision, as described in 49 CFR 173.4a and 337.2, must be prepared following Packaging Instruction 10B in Appendix C. Mailers entering mailpieces under the USPS excepted quantity provision must meet the requirements for packaging materials, and mailpieces must be in compliance with the package tests regulations in 49 CFR 173.4a. Each mailpiece must bear a DOT-approved excepted quantity marking (see 325.4) on the address side of the mailpiece, and if applicable, include documentation as provided in 49 CFR 173.4a.