A liquid is any substance that flows readily and assumes the form of the container, but retains an independent volume. For the purposes of mailability, a liquid may be a cream or paste or any other nonhazardous substance (except a gas) that may liquify under existing conditions.
An odor is any matter that is a source of an obnoxious odor.
- Liquids and powders that are nonhazardous (i.e., not regulated as hazardous materials) are mailable provided they are properly packaged as specified in 451.3.
- Any matter that is a source of an obnoxious odor is nonmailable.
Liquids and powders that are corrosive, explosive, flammable, toxic, or otherwise hazardous are subject to the mailing conditions for hazardous materials in Chapter 3, as applicable.
The following applies when mailing cremated remains (ashes):
- Domestic: Permitted for cremated human or animal remains only when sent via Priority Mail Express service. The identity of the contents should be marked “cremated remains” (Label 139 preferred) on the address side of the mailpiece. The item must be packaged as required in 451.3b and Packaging Instruction 10C.
- International: When permitted by the destination country, cremated remains may only be sent via Priority Mail Express International service. Mailers must verify that the destination country accepts Priority Mail Express International and cremated remains prior to mailing. The contents must be indicated on the applicable customs declaration form. Label 139, Cremated Remains, may optionally be applied to the address side of the mailpiece. The item must be packaged as required in 451.3b and Packaging Instruction 10C.
The following conditions apply:
- Liquids. Nonhazardous liquids, creams, and pastes, particularly those in 1-gallon paint cans with only friction-top closures (push-down tops), are often a source of damage to other mail and postal equipment. The proper packaging of liquids is critical to ensuring the integrity of the mailpiece during handling. Mailers must mark the outer container of a mailpiece containing liquid to indicate the nature of the contents, and include orientation arrows in accordance with 226. All liquids are subject to the general packaging requirements in DMM 601.3.4 and the following:
- Containers having friction–top closures are not acceptable by themselves. Such containers must be packed within a strong and securely sealed outer packaging.
- The use of locking rings or similar devices is encouraged when mailing containers with friction-top closures (push-down tops).
- Screw caps with a minimum of one and one–half turns, soldering clips, or other effective means must be used to ensure a secure closure.
- All nonmetal containers of liquid more than 4 ounces, including plastic containers, and metal containers with friction top closures, must be triple-packaged, and include absorbent material capable of absorbing all of the liquid in the container(s) in case of breakage, a leakproof secondary container, such as a watertight can or plastic bag surrounding the primary container(s), and an outer mailing container that is securely sealed, strong enough to protect the contents, and durable enough to withstand normal processing in Postal Service networks.
- Steel pails and drums with carrying handles and positive closures (e.g., locking rings or recessed spouts under screw–cap closures) may be accepted without additional packaging.
- As an alternative to 451.3a(4) above, mailers may use containers certified by the International Safe Transit Association (ISTA) to have passed ISTA‘s Test Procedure 3A. Mailers must, upon request, provide written test results verifying that sample mailpieces passed each test outlined in the standard and that no liquids were released.
- Powders and Cremated Remains. Dry materials that could cause damage, discomfort, destruction, or soiling upon escape (leakage) must be packed in siftproof containers or other containers that are sealed in durable siftproof outer containers.