Mailing Hazardous Items? A Guide to USPS Pub 52

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Shipping potentially hazardous items through the United States Postal Service (USPS) requires understanding specific regulations to ensure safety and compliance. USPS Publication 52, titled “Hazardous, Restricted, and Perishable Mail,” provides the official guidelines for mailing these materials.

This guide explains what constitutes hazardous materials according to USPS standards and what you can legally mail under specific conditions.

What Are Hazardous Materials?

The USPS, following U.S. Department of Transportation (DOT) guidelines, defines a hazardous material as any article or substance that could pose an unreasonable risk to health, safety, or property during transportation. These items are referred to as “dangerous goods” in international shipping.

It’s your responsibility as the sender to check USPS Publication 52 to determine if your item is considered hazardous.

The Nine Hazard Classes

Hazardous materials are categorized into nine distinct classes:

1. Explosives: Items designed to detonate or rapidly combust
2. Gases: Flammable, non-flammable, and toxic gases
3. Flammable and Combustible Liquids: Liquids that easily ignite
4. Flammable Solids: Materials that readily catch fire, spontaneously combust, or emit flammable gases when wet
5. Oxidizing Substances and Organic Peroxides: Materials that cause or enhance combustion
6. Toxic and Infectious Substances: Materials harmful if inhaled, swallowed, or contacted, including pathogens
7. Radioactive Materials: Items that emit ionizing radiation
8. Corrosives: Substances that can chemically damage other materials or living tissue
9. Miscellaneous Hazardous Materials: Other hazards not fitting into classes 1-8, including lithium batteries, dry ice, and magnetized materials

Mailability: What Can You Send?

USPS categorizes items into three groups:

1. Prohibited Items: Never allowed in the mail system. Examples include air bags, ammunition, gasoline, liquid mercury, and marijuana (regardless of purpose).
2. Restricted Items: Allowed in the mail under specific conditions and when following all rules in Pub 52.
3. Hazardous Materials (HAZMAT): Can be either prohibited or restricted depending on the substance and specific mailing requirements.

To determine if a specific hazardous substance can be mailed, consult the “Postal Service Hazardous Materials Table” in Appendix A of Pub 52.

Some hazardous materials can be mailed under “Limited Quantity” and “Excepted Quantity” provisions, which allow smaller amounts with reduced packaging and labeling requirements.

How to Determine if Your Item Can Be Mailed

Follow these steps to check if your potentially hazardous item is mailable:

1. Identify the exact name and composition of your item
2. Access the current version of USPS Publication 52 on the USPS Postal Explorer website
3. Use the Table of Contents or Index (Appendix G) to find information about your item
4. For likely hazardous items, check Chapter 3 and review Section 31 for the definition of hazardous materials
5. Determine which of the nine hazard classes your item might fall under (Section 33)
6. Read the specific regulations in Section 34, “Mailability by Hazard Class”
7. Check Appendix A (Hazardous Materials Table) and search for your item by name or UN identification number
8. Note any conditions like quantity limitations, packaging requirements, and labeling instructions
9. Consider your shipping method – some items are restricted to ground transportation only
10. If you’re still uncertain, visit your local Post Office or contact the USPS Product Classification Office

Packaging Requirements

Proper packaging is mandatory for mailing any permissible hazardous material. Detailed instructions are in Chapter 3 and Appendix C of Pub 52.

General Packaging Guidelines:

• Use strong, suitable containers in good condition
• Ensure containers are properly sealed to prevent leaks
• For liquids and certain materials, use secondary containment (leak-proof or sift-proof)
• Include absorbent material for liquids to soak up contents in case of leakage
• Use cushioning to prevent movement and protect contents
• Securely seal outer packaging to prevent accidental opening
• For items over 20 pounds, use rigid outer packaging meeting edge crush or burst test requirements
• Small button cell batteries cannot be placed in padded envelopes or poly bags

For specific hazardous materials, check the corresponding USPS Packaging Instruction in Appendix C for precise details on container types, cushioning materials, and sealing methods.

Labeling and Marking Requirements

Proper labeling of hazardous materials packages is legally required. These markings alert postal workers about potential hazards. Detailed instructions are in Chapter 2 (Section 22) and Chapter 3 (Section 325) of Pub 52.

Required Labels and Markings May Include:

• DOT Hazardous Materials Warning Labels: Diamond-shaped labels indicating the specific hazard class
• Limited Quantity Markings: Square-on-point label for materials in limited quantities
• Excepted Quantity Labels: For very small amounts of certain hazardous materials
• Proper Shipping Name and UN Number: Must be clearly marked on the address side
• Complete Sender and Recipient Information: Always required
• Lithium Battery Markings: DOT-approved lithium battery mark with appropriate UN number for packages containing lithium batteries
• Orientation Arrows: Required for packages containing liquids, placed on at least two opposite sides

All labels and markings must be durable, legible, and clearly visible on the address side of the package.

Common Hazardous Items: Specific Rules

Perfumes and Colognes

• Classification: Usually Flammable Liquids (Class 3) due to alcohol content
• Air Transportation: Prohibited
• Ground Transportation: Permitted within the United States
• Packaging Requirements: Spill-proof primary container, cushioning, strong outer container
• Additional Notes: Place primary container in sealed bag, include absorbent material to soak up potential leaks, mark outer container as “Flammable Liquid,” add orientation arrows

Nail Polish and Removers

• Classification: Typically Flammable Liquids (Class 3)
• Air Transportation: Restricted or prohibited
• Ground Transportation: Permitted if qualifying as “consumer commodity” within quantity limits
• Packaging Requirements: May require triple packaging for liquids
• Additional Notes: Mailer must know flashpoint and toxicity (check manufacturer’s Safety Data Sheet)

Electronics with Lithium Batteries

• Classification: Class 9 (Miscellaneous Hazardous Materials)
• Air Transportation: Permitted with conditions
• Ground Transportation: Permitted
• Packaging Requirements: Rigid outer packaging with proper cushioning
• Additional Notes:
  • For domestic air shipping: Maximum 8 cells or 2 batteries when installed in new or Manufacturer Certified Refurbished equipment (11-pound limit)
  • Individual batteries (not in equipment): Ground transportation only (5-pound limit)
  • International rules are stricter, generally allowing only properly installed batteries
  • Used, damaged, or defective devices: Ground transportation only, marked “Restricted Electronic Device” and “Surface Transportation Only”

Aerosol and Liquid Cleaning Products

• Classification: Often Flammable Gases (Class 2) or may be corrosive (Class 8)
• Air Transportation: Usually prohibited for flammable aerosols
• Ground Transportation: Often permitted with restrictions
• Packaging Requirements: Depends on specific product
• Additional Notes: Quantity limits often apply (e.g., 1-liter limit per package for metal cans of flammable gases)

Exceptions and Special Cases

USPS Pub 52 includes some exceptions to standard rules:

• Small Quantity Exception: Allows mailing very limited amounts (30 ml or 30g) of certain hazardous materials via domestic ground transportation with reduced requirements
• Button Cell Exception: Special rules for very small lithium cells and batteries (like button cells) when installed in equipment for international mail
• For other exceptions, check Section 337 for Excepted Quantities

Penalties for Non-Compliance

Failing to comply with USPS regulations for hazardous materials can result in:

• Civil and criminal penalties
• Fines up to $100,000 per violation
• Liability for cleanup costs and damages

USPS personnel are trained to identify nonmailable hazardous materials. When discovered, such items may be refused, removed from the mail stream, and reported to authorities.

Staying Current with Regulations

• USPS Pub 52 is updated regularly, typically at least once a year
• Check the USPS Postal Explorer website for the most current version
• Review the “Summary of Changes” document with each new edition
• Updates are announced in the Federal Register and Postal Bulletin

International Shipping Considerations

International regulations for hazardous materials are generally more restrictive:

• Most hazardous materials cannot be mailed internationally, including to APO, FPO, and DPO locations
• Even items mailable domestically might be prohibited internationally
• Consult Chapter 6 of Pub 52 for international shipping regulations

Air vs. Ground Transportation

There are important differences between shipping hazardous materials by air versus ground:

• Air transportation regulations are much stricter due to increased safety risks
• Many flammable liquids and aerosols are restricted to ground transportation only
• Hazardous materials intended for ground transportation must have specific endorsements if forwarding, return, or address-correction service is requested
• See Chapter 7 of Pub 52 for air transportation requirements

Summary of Common Items

Mailing hazardous items requires careful attention to USPS Publication 52 guidelines. Understanding hazard classes, mailability rules, packaging requirements, and labeling instructions ensures safety and compliance. When in doubt, consult the latest version of Pub 52 or seek guidance from your local Post Office.

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