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Shipping liquids through the United States Postal Service (USPS) involves navigating specific regulations designed to ensure safety and prevent damage during transit. These rules are essential for individuals and businesses to avoid delays, returns, or penalties.
What Qualifies as a Liquid?
USPS defines a liquid broadly as any non-hazardous substance (excluding gases) that:
- Flows
- May exist as a cream or paste
- Has the potential to liquefy under existing conditions
Non-Hazardous vs Hazardous Liquids
Non-Hazardous Liquids
- Generally mailable with proper packaging
- Must prevent leakage and potential damage
Hazardous Materials (HAZMAT)
- Substances that pose risk of injury or damage
- Include flammable, corrosive, or toxic liquids
- Subject to stricter regulations
USPS prohibits mailing any material that produces an obnoxious odor, regardless of hazard classification.
Domestic Shipping of Non-Hazardous Liquids
Non-hazardous liquids, creams, and pastes can be shipped domestically if properly packaged to prevent leakage.
Packaging Requirements
- Outer Container Marking:
- Must clearly indicate contents are liquid
- Must include orientation arrows
- Containers with Friction-Top Closures:
- Not acceptable on their own
- Must be packed within strong, securely sealed outer packaging
- Locking rings or similar devices recommended
- Primary Container Requirements:
- Must have secure closure
- Screw caps need minimum of 1.5 turns
- Soldering clips or other means used to ensure container remains closed
- Triple Packaging for:
- Nonmetal containers holding more than 4 ounces of liquid
- Metal containers with friction-top closures
- Primary container
- Absorbent material capable of absorbing all liquid if breakage occurs
- Leakproof secondary container (watertight can or plastic bag)
- Strong outer mailing container
Exception: Steel pails and drums with carrying handles and positive closures (locking rings or recessed spouts under screw-cap closures) may be accepted without additional packaging.
Alternative Packaging
Mailers can use containers certified by the International Safe Transit Association (ISTA) that have passed ISTA’s Test Procedure 3A. Written test results must be available upon request.
Domestic Shipping of Hazardous Liquids
Hazardous materials present higher risks and face stricter regulations. Many common household products are classified as hazardous.
Flammable Liquids
- Definition: Liquids with flashpoint not exceeding 140°F (60°C)
- Flashpoint below 20°F (-7°C): Prohibited from mailing
- Gasoline: Nonmailable under any circumstances
- Flashpoint 20°F to 100°F (38°C): Acceptable for domestic mail via surface transportation only if:
- Meet criteria for “Limited Quantity” ground material
- Adhere to Packaging Instruction 3A
- Flashpoint 100°F to 140°F: May be reclassified as combustible liquids
Combustible Liquids
- Definition: Flashpoint above 140°F (60°C) but not more than 200°F (93°C)
- Air transportation: Permitted if qualifying as ID8000 material and meeting criteria in Exhibit 343.22 of Publication 52 (Packaging Instruction 3B)
- Surface transportation: Allowed if qualifying as “Limited Quantity” and “consumer commodity” material (Packaging Instruction 3B)
Other Hazardous Properties
- Corrosiveness: Packaging Instruction 8A
- Toxicity: Packaging Instruction 6A
Prohibited Hazardous Liquids
- Gasoline
- Liquid mercury and devices containing visible amounts (older thermometers and barometers)
- Pure chemicals like acetone, benzene, and hexane (unless sufficiently diluted)
Shipping Requirements for Hazardous Liquids
- Consult Appendix C of Publication 52 for specific packaging instructions
- Display appropriate DOT diamond-shaped hazardous materials warning label for commercial shipments
- Apply approved DOT Limited Quantity surface mark for surface transportation of certain flammable and combustible liquids
- Safety Data Sheet (SDS) may be necessary to determine proper handling procedures
- Many flammable liquids restricted to ground transportation only
International Shipping of Liquids
International shipping rules are more restrictive than domestic regulations.
General International Restrictions
- Must comply with both USPS regulations and destination country rules
- Many liquids mailable domestically are prohibited internationally
Common Prohibited Items for International Shipping
- Aerosols
- Alcoholic beverages
- Gasoline
- Nail polish
- Perfumes containing alcohol
- Liquid mercury
- Flammable and combustible liquids
Always check the International Mail Manual (IMM) and individual country listings on the USPS website for specific regulations.
Most hazardous materials are nonmailable to international destinations, including APO, FPO, and DPO locations.
Special Categories of Liquids
Alcoholic Beverages
- Beverages with alcohol content of 0.5% or more generally nonmailable both domestically and internationally
- Taxable liquors with 3.2% or less alcohol also prohibited
- Limited exceptions:
- Products containing intoxicating liquor meeting IRS and FDA requirements
- Non-taxable, non-poisonous, non-flammable products (cold remedies, cooking wine, mouthwash)
- Intoxicating liquor sent between federal or state agency employees for official use
- Advertising materials soliciting mailing of intoxicating liquors are nonmailable
- Private individuals cannot ship alcohol as gifts via USPS
Cosmetics
- Non-flammable and non-hazardous cosmetics: Generally permitted domestically with proper packaging
- Perfumes containing alcohol: Flammable, only shipped domestically via ground transportation, prohibited for international shipping
- Nail polish and remover: Flammable, may be restricted to ground transportation domestically, prohibited internationally
- Aerosol sprays (hairspray): Classified as hazardous, often limited to ground transportation domestically, prohibited internationally
- Packaging requirements: Secure containers, absorbent material where necessary, strong outer packaging
Medications
- Prescription drugs: Generally only mailable by DEA-registered distributors to the prescribed patient
- Exceptions: Returning medications to manufacturers or when sender and recipient are exempt from DEA registration
- Over-the-counter drugs: Can be mailed by anyone if complying with laws and packaging regulations
- Controlled substances: Heavily regulated, often prohibited unless specific conditions are met
- International regulations: Vary by country, must adhere to destination country’s laws
Biological Samples for Testing
- Category A infectious substances: Not mailable internationally
- Category B infectious substances: Mailable internationally under strict conditions:
- Limited quantities
- Triple packaging
- Specific labeling (“Biological substance, Category B” and UN 3373)
- Must use First-Class Package International Service with Registered Mail
- Limited to authorized laboratories sending to accepting foreign counterparts
- Nonregulated (noninfectious) materials: Mailable domestically and internationally with Packaging Instruction 6G
- Exempt human/animal specimens: Mailable with triple packaging and marked appropriately
Proper Packaging for Liquid Shipments
Step-by-Step Guide
- Seal the Primary Container:
- Ensure tight closure
- Consider using waterproof tape for added security
- Use a Leak-Proof Bag:
- Place sealed primary container inside leak-proof plastic bag
- Ziploc or adhesive seal bags work well
- Add Absorbent Material:
- Required for nonmetal containers over 4 ounces and metal containers with friction tops
- Use packing peanuts, cellulose wadding, or paper towels
- Must be sufficient to absorb entire liquid contents if container breaks
- Use a Secondary Container (if required):
- Place primary container (in leak-proof bag with absorbent material) inside another sealed, leakproof container
- Can be a watertight can or rigid plastic container
- Cushion Thoroughly:
- Place container(s) inside sturdy outer box
- Use ample cushioning material (bubble wrap, packing peanuts, crumpled paper)
- Prevent movement and protect against shocks
- Seal the Outer Box:
- Use strong packing tape on all flaps and edges
- Consider Temperature Control:
- For temperature-sensitive liquids, use insulated boxes and cold packs as needed
- Add Orientation Arrows:
- Clearly indicate correct upright position
Proper Labeling Requirements
- Complete delivery and return addresses on outer packaging
- Mark outer container with the word “Liquid”
- Affix orientation arrows
- For hazardous liquids: appropriate DOT diamond-shaped warning label
- For limited quantity flammable/combustible liquids: DOT Limited Quantity surface mark
- For Category B infectious substances: “Biological substance, Category B” marking, UN 3373 identification, and biohazard symbol
- For exempt specimens: “Exempt human specimen” or “Exempt animal specimen” marking
- Remove old markings or labels on reused packaging
Summary Tables
Common Liquids for Domestic Shipping
| Liquid Type | General Mailability | Key Restrictions/Conditions |
|---|---|---|
| Non-Hazardous Liquids | Allowed | Proper packaging required (marking, orientation, container type, potential triple packaging) |
| Flammable Liquids (Flashpoint < 20°F) | Prohibited | Gasoline always prohibited |
| Flammable Liquids (20°F – 100°F) | Allowed – Ground Only | “Limited Quantity” guidelines, Packaging Instruction 3A |
| Combustible Liquids (100°F – 200°F) | Allowed (with conditions) | Air: ID8000 material requirements<br>Ground: “Limited Quantity” & “consumer commodity” |
| Alcoholic Beverages (≥ 0.5% alcohol) | Prohibited | Limited exceptions for specific products and official use |
| Perfumes (Alcohol-Based) | Allowed – Ground Only | Proper packaging required |
| Nail Polish | Allowed – Ground Only | Considered flammable |
| OTC Medications | Allowed | Comply with laws, proper packaging |
| Prescription Medications (by Individual) | Prohibited | Only allowed by DEA-registered distributors with exceptions |
| Mercury (Liquid) | Prohibited | Devices containing visible amounts also prohibited |
Common Liquids Prohibited for International Shipping
| Liquid Type | Reason for Prohibition |
|---|---|
| Aerosols | Potential flammability, pressure changes in air travel |
| Alcoholic Beverages | Generally prohibited by federal law and international regulations |
| Gasoline | Highly flammable |
| Nail Polish | Flammable |
| Perfumes (Containing Alcohol) | Flammable |
| Liquid Mercury | Toxic and hazardous |
| Combustible Liquids | Generally prohibited |
Conclusion
Shipping liquids via USPS requires careful attention to regulations. Always check the official USPS website and Publication 52, Hazardous, Restricted, and Perishable Mail for the most current information before shipping any liquids.
Compliance with all applicable USPS regulations is the mailer’s responsibility, and failure to comply can result in penalties. Following these guidelines diligently helps ensure safe and successful shipping through the USPS network.
Our articles make government information more accessible. Please consult a qualified professional for financial, legal, or health advice specific to your circumstances.
