USPS Hazmat Shipping Guidelines – How to Ship Fast While Staying Compliant

Hazardous Materials

What is a Hazardous Material?

For many eCommerce brands and sellers, there are already lots to think about when shipping orders – you need to send inventory to warehouses, have shipping labels printed, and pick, pack and ship items correctly. 

However, some sellers sell products that require extra diligence, care, and attention while shipping them. Shipping Hazardous Materials, or HAZMAT as they’re commonly called, can be complex. In June 2023, the United States Postal Service (USPS) announced a number of changes to the guidelines sellers have to follow while shipping HAZMAT items. Following these guidelines is important for sellers to maintain compliance and mitigate regulatory risks, while also ensuring the safety of USPS staff who ship and deliver your packages.

A lot of sellers may not be aware of the extent and impact of these new changes. Failing to comply with the new requirements can cause significant damage to your brand. In this article, we’ve compiled everything you need to know about HAZMAT shipping. 

We start by understanding the definition of a hazardous material and what items are classified as HAZMAT. We then take a deep-dive into how the Postal Service was handling HAZMAT previously and what has changed in the latest requirements. We examine why the USPS might be making these changes and the potential penalties you face for non-compliance. Lastly, we look at what your fulfillment partner must do to ship your orders in a compliant manner, keeping your brand, USPS personnel, and your customers safe. 

What Items Are HAZMAT?

The Postal Service classifies every hazardous material into one of nine categories.

Classes of HAZMAT Items

Let’s first examine these categories, understanding their definitions, example items that fall into them, and the risks they can pose to people, the environment, or property. 

You can use this as a template to do a preliminary analysis of whether your items are likely to fall into any of these HAZMAT categories.

Hazard Class
Example Items
1.1 – 1.6
Explosives with varying characteristics
Fireworks, dynamite, and ammunition (small arms)
Can vary from a massive explosion to low sensitivity explosions.
Flammable Gasses
Lighter fluid, Propane, and Butane
Fire hazards and explosion risks
Non-Flammable, Non-Toxic Gasses
Nitrogen (for tires), Carbon Dioxide (fire extinguisher)
No fire hazard, asphyxiation risk
Toxic Gasses
Household Cleaners (Ammonia), Bleach
Toxic inhalation hazard
Flammable Liquids
Gasoline, Rubbing Alcohol, Lighter Fluid
Fire hazard
Flammable Solids
Matches, Lighter Cubes, Firestarters
Fire hazard, may contribute to combustion
Spontaneously Combustible Solids
Spontaneous Combustion Firestarters
Can ignite spontaneously
Dangerous When Wet
Fertilizers (contains Ammonium Nitrate), Sodium (in water)
Can release flammable gas when in contact
Oxidizing Substances
Hydrogen Peroxide (in hair bleach), Nitric Acid (in fertilizers)
Enhances combustion, fire risk
Organic Peroxides
Acne Creams (Benzoyl Peroxide), Hair Bleaching Kits (contains peroxide)
Fire and explosion risk
Toxic Substances
Pesticides (e.g., Insecticides), Household Cleaners (contains toxins)
Toxic to humans
Infectious Substances
Medical Waste, Biological Cultures (e.g., from labs)
Risk of spreading diseases
Radioactive Materials
Smoke Detectors (contains Americium), X-ray Machines (used in medical facilities)
Ionizing radiation hazard
Corrosive Substances
Drain Cleaner (contains Sulfuric Acid), Alkaline Batteries
Corrosive to materials, skin, eyes
Miscellaneous Hazardous Materials
Lithium Batteries (found in electronics), Asbestos-containing Materials
Various hazards depending on the material

What Classes Can Ship Using USPS Services?

Based on the class of item your product falls into, it may or may not be allowed on Ground or Air services in the US or International shipping. 

You can use this as a resource to understand whether your item is allowed to ship, and what services it can be sent through. 

Substantial portions of this chart are based on Publication 52 – Hazardous, Restricted and Perishable Mail from the USPS.

For more information on a specific hazard class or regulation, refer to Publication 52. For help with a specific SKU you’re trying to ship, refer to the Postal Service’s HAZMAT Shipping tool.

Explosives With Varying Characteristics (1.1 to 1.6)
Prohibited Class 1.4 (Minor Explosion Hazard) may be shipped, only with prior approval from USPS Headquarters as per 341.2c of Publication 52
Flammable Gasses (2.1)
Only as Limited Quantity Surface Material, per 342 of Publication 52
Non-Flammable, Non-Toxic Gasses (2.2)
Only as Limited Quantity Surface Material, per 342
Permitted if material qualifies as ID8000, per 342
Toxic Gasses (2.3)
Flammable Liquids (3)
Only as Limited Quantity Surface Material, per 343
Prohibited Combustible liquids are permitted if material qualifies as ID8000 per 343
Flammable Solids (4.1)
Only as Limited Quantity Surface Material, per 344
Spontaneously Combustible Solids (4.2)
Only as Limited Quantity Surface Material, per 344
Dangerous When Wet (4.3)
Only as Limited Quantity Surface Material, per 344
Oxidizing Substances (5.1)
Only as Limited Quantity Surface Material, per 345
Only as Limited Quantity Air Material, per 345
Organic Peroxides (5.2)
Only as Limited Quantity Surface Material, per 345
Only as Limited Quantity Air Material, per 345
Toxic Substances (6.1)
Only as Limited Quantity Surface material per 346. Other poisons may ship as permitted in 346.231
Permitted if it qualifies as ID8000 material per 346. Other poisons may ship as permitted in 346.231
Infectious Substances (6.2)
Only as permitted in 346
Only as permitted in 346
Only First-Class Package International Service with Registered Mail service per 622
Radioactive materials (7)
Only per 347
Only First-Class Package International Service with Registered Mail service per 622
Corrosive Substances (8)
Only Limited Quantity Surface material per 348
Only Limited Quantity Air material per 348
Miscellaneous Hazardous Materials (9)
Only Limited Quantity Surface material and other materials as permitted in 349
ID8000 material and other materials as permitted in 349
Prohibited, except for magnetized materials per 349 and 622.4 and lithium batteries per 622.5

What Changes Has USPS Recently Made To HAZMAT?

Recently, the USPS has been making a number of changes to the way it handles and processes HAZMAT shipping. 

These have important implications for sellers. In this section, we take a look at each of them: 

Declaring HAZMAT During Label Generation

USPS now requires shippers to officially declare that packages contain HAZMAT when they purchase shipping labels. 

The shipping label consequently clearly indicates this, making it easy for USPS staff to handle the shipment with the required care.

Items Allowed on Ground vs. Air

Recently, USPS has begun restricting electronic devices that are used, damaged, or defective to ground services alone. 

These packages must now be labeled as ‘Restrictive Electronic Devices’ for ‘Surface Transportation Only’.

Separation of HAZMAT And Non-HAZMAT Items

The USPS has also begun requiring that HAZMAT and non-HAZMAT items must be clearly separated into different parcels or mail receptacles. The HAZMAT parcels need to have clear marking and identification.

Why Have These Changes Been Made?

Why is there suddenly an increased focus on these compliance requirements from the Postal Service? Many shippers have been used to operating without any changes to requirements for a long time and might be surprised about why these changes are taking place now. 

In this section, we’ll take a look at why USPS is enforcing these new requirements, as well as the risks you face if you don’t comply with them.

Safety of USPS Personnel and Transportation

According to Shippo’s estimates, over 10,000 safety incidents involving HAZMAT shpping were reported in the first nine months of the 2020 fiscal year. That number has continued rising – in 2022, there were over 25,000 HAZMAT incidents reported. 

Such incidents pose significant risks for USPS personnel, the environment, property and other people sharing the road or airspace during their transportation. In a bid to reduce this impact and improve overall safety outcomes, these new requirements are being enforced. 

More Reliable On-Time Delivery

While these incidents are detrimental from a health and safety perspective, that isn’t their only negative. They disrupt operations and delay deliveries. In fact, Shippo estimates that packages are delayed by an average of 2 weeks after such incidents. 

With USPS aiming to compete more aggressively in parcel delivery with the likes of UPS and FedEx, an increasing accident rate can lower their delivery SLAs and affect service levels for all shippers. 

USPS’ latest regulations are aimed at streamlining their network operations and reducing downtime and disruptions.

Penalties For Non-Compliance

As the number of HAZMAT shipping related incidents is on the rise, failure to comply could affect your brand’s ability to conduct operations normally. With health, safety, and lives at stake – the penalties for noncompliance are heavy. Here are the possible penalties:

  • Your shipments could be denied entry into the USPS mailstream – affecting your ability to meet customer delivery promises. 
  • For serious infractions, the US Department of Transportation can pursue civil penalties. 
  • The maximum penalty for Hazardous Materials violation is $89,678. However, if the violation results in death, serious illness, severe injury to an individual or significant damage to property, you could be fined as much as $209,249. 

Such incidents can be financially damaging, affect your brand’s reputation and in some cases even threaten its very existence. 

What Should You and Your 3PL Do While Shipping HAZMAT?

Identify Your HAZMAT SKUs Using Product SDS

The first question you might have is – which of my SKUs are HAZMAT? The quickest way to identify this is using the Product Safety Data Sheet (SDS). What is a Safety Data Sheet? 

A Safety Data Sheet (SDS) is a document that provides detailed information about the properties, hazards, and safe handling procedures of a product. It includes essential details such as the product’s composition, physical and chemical characteristics, potential health and environmental hazards, safe usage guidelines, emergency response measures, and regulatory information.

You can use the SDS database to locate your product’s safety sheet. 

On it, you’ll need to go to Section 14, which provides transportation information, including the category that DOT classifies the product under. Using this, you can understand which USPS services can be used to ship the item, as well as specific marking / labeling, and packaging requirements.

Properly Designate HAZMAT SKUs on Shipping Software

You need to designate your HAZMAT SKUs on your shipping software. This is important for a number of reasons: 

  • This can be transmitted to USPS when purchasing labels, so that they know you are shipping HAZMAT.
  • It helps your fulfillment partner affix the right marking / labels when packing these items. 
  • It helps your fulfillment partner package these items the right way. 

Having your SKUs properly designated on a digital system of record is the best way to ensure defect-free, compliant fulfillment. Relying on spreadsheets or human-to-human conversation can lead to potentially costly lapses.

Adhere to Packaging Requirements

While shipping HAZMAT, you must make sure to follow packaging requirements to keep your items secure and spill or leak-proof. 

Your fulfillment partner must have deep knowledge of what HAZMAT SKUs you are shipping, and then package them in accordance with the specific requirements laid out in Appendix C of Publication 52.

While the details can vary significantly based on the item, these are broad best-practice guidelines applicable across most items. Following these packaging practices requires industry-leading fulfillment standards from your 3PL. Warehouse staff must make sure to diligently pack each SKU in the best possible way on every order.

  • Inner Packaging

  • Employ inner packaging that is compatible with the specific hazardous material but also capable of withstanding the conditions of transportation.
  • Inner packaging must be leak-tight for liquids and gas-tight for gasses, preventing unintended release during transit.

  • Outer Packaging

  • Utilize robust outer packaging that serves as a primary barrier to protect the inner packaging and the contents from external forces and potential hazards.
  • Choose outer packaging materials that are suitable for the specific characteristics of the hazardous material being shipped.

  • Cushioning and Absorption

  • An effective cushioning system safeguards the inner packaging from movement and potential damage during transit, providing an additional layer of protection.
  • For liquids, incorporate absorbent materials within the packaging to contain and manage spills, preventing leakage that could pose safety and environmental risks.

  • Closure and Sealing

  • Ensure secure closure and sealing of packages to prevent any leakage or spillage during transportation.
  • Verify that closures meet regulatory standards and are appropriate for the specific hazardous material being shipped, maintaining the integrity of the package.

  • Overpack Requirements

  • If applicable, employ overpacking techniques as an additional layer of protection and consolidation for smaller packages.
  • Overpacks should not only consolidate packages but also be designed to contain leaks or spills, providing an extra measure of safety.

  • Compatibility

  • Package hazardous materials with a keen focus on preventing any reactions between different substances within the package.
  • Separation of incompatible materials within the packaging ensures that any potential chemical reactions are avoided, maintaining the safety and stability of the shipment.

  • Quantity Limits

  • Adhere strictly to quantity limits specified for each hazardous material to prevent overloading and ensure compliance with safety regulations.
  • Packaging must be designed to accommodate the specified quantity, preventing any compromise in the safety of the contents.

Adhere to Marking and Labeling Requirements

When shipping HAZMAT items, it is important to affix various marking labels onto the package that provide information to USPS staff about what the package contains. 

This helps them handle the package the right way, and ensure higher safety standards. While these can vary significantly by product, here are a few common marking / labeling practices required for HAZMAT items. For your specific SKU, make sure to refer to Appendix C of Publication 52.

Your 3PL must be capable of mapping each SKU you have to its specific labeling requirements. This detail-oriented rigor must be backed up by defect-free, high-quality  fulfillment standards that ensure each package has all the necessary labels on it.

  • Hazard Class Labels

  • Hazard class labels need to be affixed to the outer packaging, indicating the primary hazard class or division of the material.
  • Ensure hazard class labels are prominently displayed, providing USPS staff a quick visual identification of the potential risks associated with the shipment.

  • Handling Labels

  • Mark packages with handling labels, communicating specific instructions on how to safely handle them during transportation.
  • Clear and concise handling labels contribute to the safe and proper management of the package during transit.

  • Identification Numbers

  • Clearly display proper shipping names and identification numbers on the outer packaging.
  • This information assists in identifying the material and its associated hazards, aiding in emergency response and handling procedures.

  • Limited Quantity Marking

  • If applicable, mark packages with the “Limited Quantity” marking to indicate compliance with quantity limitations for certain hazardous materials.
  • This marking is crucial for packages that qualify for reduced regulatory requirements.

  • Overpack Marking

  • For overpacks, mark them appropriately to indicate that they contain hazardous materials.
  • Overpack markings help handlers and emergency responders quickly identify packages that include multiple smaller packages.

  • Orientation Arrows

  • On packages containing liquids, include orientation arrows to indicate the correct orientation for safe handling.
  • Proper orientation ensures that liquids are transported in a manner that minimizes the risk of leaks or spills.

  • Elevated Temperature Marking

  • If applicable, mark packages containing materials at elevated temperatures to communicate the additional risks associated with heat.
  • This marking ensures awareness of temperature-related hazards during transportation.

Declare HAZMAT During Label Generation

 If you’ve designated your SKUs as HAZMAT in your shipping software, this step shouldn’t be too difficult! 

When generating labels, your shipping software needs to inform USPS that you’re shipping HAZMAT. This allows the Postal Service to prepare to handle your items the right way. 


With an increased focus on the safety of its personnel and the performance of its network, the USPS has rolled out these new HAZMAT changes. 

Many, many items fall under HAZMAT, and a lot of them may not be immediately obvious as meeting the classification. With increased penalties and regulations, it is important for shippers to carefully scan their product catalog for HAZMAT SKUs and then ship them following all necessary protocols.

This takes deep attention to detail, high quality fulfillment standards, and solid technology at your fulfillment partner’s end. Shipping HAZMAT items can seem daunting – but with the right fulfillment partner, you’ll be able to ship them as seamlessly as your other SKUs. Good luck, and happy shipping! 

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