45 Other Restricted Materials

451 Liquids, Powders, and Odor-Producing Materials

451.1 Definitions

The following definitions apply:

1. Liquid: Any substance that flows readily and assumes the form of its container while retaining an independent volume. For the purposes of mailability, a liquid or any other nonhazardous substance (except a gas) that may liquify under existing conditions.
2. Powders: Dry materials that could cause damage, discomfort, destruction, or soiling upon escape (leakages).
3. Odor-Producing Materials: Any matter that is a source of an obnoxious odor.

451.2 Mailability

The following conditions apply for mailing liquids, powders, and odor-producing materials:

1. Liquids that are nonhazardous (i.e., not regulated as hazardous materials) are mailable provided they are properly packaged as specified in 451.3.
2. Powders must be packed in sift-proof containers or other containers that are sealed in durable sift-proof outer containers.
3. Any matter that is a source of an obnoxious odor is nonmailable.

451.21 Restrictions

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.

451.22 Cremated Remains

The following applies when mailing cremated human or animal remains (ashes):

1. Domestic Mail:
1. Service Required: Cremated remains may only be mailed domestically when sent via Priority Mail Express service, utilizing USPS-produced cremated remains packaging (BOX-CRE). These remains must be packaged according to 451.3(b) and Packaging Instruction 10C in Appendix C must be followed.
2. Shipping Labels: Shipping labels may be printed and affixed at a Post Office location, or single-ply Priority Mail Express labels can be generated through Click-N-Ship or other Postal Service-approved methods. Mailer-generated labels must display an Intelligent Mail package barcode (IMpb) with the correct cremated remains service type code and the proper Extra Services code in the Shipping Services File (refer to Publication 199 on PostalPro at postalpro.usps.com).
3. Extra Services: Additional insurance and Return Receipt are the only extra services permitted for cremated remains.
2. International Mail:
1. Service and Destination Verification: Cremated remains (human or animal) may be sent internationally only through Priority Mail Express International service in USPS-produced cremated remains packaging (BOX-CRE) and when the destination country permits. Mailers must verify that the destination country accepts both Priority Mail Express International and cremated remains before mailing. Contents must be listed on the applicable customs declaration form. Additionally, packages must meet the requirements specified in 451.3(b), and Packaging Instruction 10C in Appendix C must be followed.

451.3 Packaging and Marking

The following conditions apply:

1. Nonhazardous Liquids, Creams, and Pastes: These items, particularly those in 1-gallon paint cans with friction-top closures (push-down tops), present a higher risk of causing damage to other mail and Postal Service equipment. Proper packaging is critical to maintaining the integrity of such mailpieces during handling. Mailers must mark the outer packaging of mailpieces containing liquid to indicate the contents and include orientation arrows in accordance with 223. All liquids are subject to the general packaging requirements per DMM 601.3.4 and the following:
1. Friction-Top Closures: Containers with friction-top closures alone are not acceptable and must be packed within a strong and securely sealed outer packaging.
2. Secure Closures: Locking rings or similar devices are recommended for containers with friction-top closures (push-down tops).
3. Secure Caps: Screw-cap closures with at least one and one-half turns, soldering clips, or other effective closures are required for a secure seal.
4. Triple-Packaging: Nonmetal liquid containers exceeding 4 ounces, including plastic containers, and metal containers with friction-top closures, must be triple-packaged. This includes:
1. Absorbent Material: Sufficient to absorb all liquid in the container(s) in case of breakage.
2. Leakproof Secondary Packaging: A watertight can or plastic bag surrounding the primary container(s).
3. Outer Packaging: Securely sealed and strong enough to protect the contents, and durable enough to withstand normal processing in Postal Service networks.
5. Exemptions for Steel Containers: Steel pails and drums with carrying handles and secure closures (e.g., locking rings or recessed spouts with screw-cap closures) are mailable without additional packaging.
6. International Safe Transit Association (ISTA) Certification Alternative: Mailers may use containers certified by the ISTA to have passed ISTA‘s Test Procedure 3A. Upon request, mailers must provide written test results verifying that sample mailpieces have met all required tests with no liquid leakage detected.
2. Powders and Cremated Remains: Dry materials that could cause damage, discomfort, destruction, or soiling if they escape (leak) must be packaged in sift-proof containers or sealed within durable, sift-proof outer containers.