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USPS: Hazardous Materials (HAZMAT)

Send hazardous materials with USPS

Written by Dan Coleman

Updated at December 13th, 2025

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In This Article

Before We Begin USPS Shipping Guidelines Specify the Shipment Contains Hazardous Materials

The USPS requires that you specify when a shipment contains any material or substance, such as chemicals or flammable items, that may injure people or cause damage when not handled properly.

This article will guide you through how to specify that your USPS shipment contains hazardous materials.

Before We Begin

Postsale supports shipping hazardous materials (HAZMAT) with USPS. This article assumes that you have at least one USPS account connected to Postsale.

When  shipping Hazardous materials, the USPS supports:

  • Domestic shipments only
  • The following USPS services:
    • USPS Ground Advantage®
    • USPS Priority Mail®
    • USPS Priority Mail Express®

USPS Shipping Guidelines

You are responsible for reviewing and complying with the USPS Domestic Shipping Prohibitions, Restrictions, and HAZMAT guidelines and with the the USPS rules surrounding shipping Hazardous Materials. This includes:

  • USPS service restrictions for specific types of hazardous materials
  • Any specific labeling requirements for the hazardous material being shipped
  • Any additional packaging requirements when shipping hazardous materials 

Per the USPS: “The Postal Service is reminding customers that metallic mercury and devices containing metallic mercury are always prohibited in the mail stream. This includes antique items such as thermometers, barometers, blood pressure monitors and similar devices.”

 

Specify the Shipment Contains Hazardous Materials

Configuring a shipment for a package that contains hazardous materials is similar to configuring any other shipment in Postsale:

  1. Verify that the correct carrier and service are selected. 
  2. Enter the correct weight and dimensions for the package.
  3. Configure any additional options.

Then, specify that the shipments contains hazardous materials:

  1. Expand the Package section in the Dock.
  2. Check the Shipment contains hazardous materials option.
  3. Select the type of hazardous material contained in the package from the Hazardous Materials Type drop-down menu.  

    Shipment contains hazardous materials is selected and the Dry Ice is selected as the type of material.
usps usps hazardous hazardous materials hazmat

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