- > Appendix C > USPS Packaging Instruction 10B
Some types of hazardous materials, as permitted in 337 and 49 CFR 173.4a, may be prepared for mailing using the excepted quantity provision. The excepted quantity provision, although applicable to international shipments by commercial shippers, is limited to domestic mail, and its use is prohibited in international and APO/FPO/DPO mail.
For liquids, intermediate containers must contain sufficient absorbent material that:
The intermediate packaging must be securely packed in strong, rigid outer packaging.
Placement of the material in the package must not violate 49 CFR 173.21.
Outer packages must be of such a size that there is adequate space to apply all necessary markings.