Publication 52, Hazardous, Restricted, and Perishable Mail > Appendix C > USPS Packaging Instruction 3D
Certain limited quantities of flammable liquids and solids containing ethyl alcohol are permitted in the domestic mail via air transportation, with special authorization from the manager, Product Classification when all applicable requirements in 343.27 are met.
Separate packaging requirements apply, dependent on the percentage of ethyl alcohol and primary container used.
For content not more than 70% ethyl alcohol:
For content more than 70% ethyl alcohol: