Hate to be rude, but the guy asked a good pertainable question and got a load of crap. I mailed denat to most of my AT maildrops and will do the same this year on the PCT. Read on (from USPS web page):
4.3Combustible Liquid Mailability
Combustible liquid is prohibited in international mail. Combustible liquid is permitted in domestic mail if the material can qualify as an ORM-D material and meet the following conditions as applicable:
a. For surface transportation, if the flashpoint is 100°F (38°C) but no more than 141°F (60.5°C); the liquid is in a metal primary receptacle not exceeding 1 gallon, or in another type of primary receptacle not exceeding 1 quart, per mailpiece; enough cushioning surrounds the primary receptacle to absorb all potential leakage; the cushioning and primary receptacle are packed in a securely sealed secondary container that is placed within a strong outer shipping container; and each mailpiece is plainly and durably marked on the address side with “Surface Only” or “Surface Mail Only” and “ORM-D” immediately following or below the proper shipping name.
b. For surface or air transportation, if the flashpoint is above 141°F (60.5°C) but no more than 200°F (93°C); the liquid is in a primary receptacle not exceeding 1 gallon per mailpiece; enough cushioning surrounds the primary receptacle to absorb all potential leakage; the cushioning and primary receptacle are packed in a securely sealed secondary container that is placed within a strong outer shipping container; and each mailpiece is plainly and durably marked on the address side with “ORM-D” or “ORM-D AIR,” as applicable, immediately following or below the proper shipping name. Mailable material sent via surface transportation must be marked on the address side as “Surface Only” or “Surface Mail Only.” For air transportation, each mailpiece must bear a shipper’s declaration for dangerous goods.
c. For air or surface transportation, if the flashpoint is above 200°F (93°C) the material is not regulated as a hazardous material. Such nonregulated materials must be properly and securely packaged to prevent leakage under the general packaging requirements in C010.
here’s the link:
http://pe.usps.gov/text/dmm/c023.htm
goldbond