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What Does USPS® Classify as Hazardous Materials?

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Items possibly containing hazardous materials

Items containing mercury or explosives

You can find information on common hazardous, restricted and perishable materials in the summarized USPS.com Shipping Restrictions page, and the detailed Publication 52, Hazardous, Restricted, and Perishable Mail which also contains the Transportation Requirements in section 327.1 Transportation Requirements 327.1. These guides identify many items by their common names and can help you determine what may be mailed and if special packaging Packaging Instruction 3A or other restrictions apply. The guide is completely searchable by keyword and links to more detailed information.

One of these guides is the "Hazardous Materials Table: Postal Service Mailability Guide," based on the online DOT Hazardous Materials Table. The information is modified to identify the mailability of each hazardous material (such as different acids and batteries) based on Postal Service mailing regulations.

A guide on making Hazardous Material shipping safer can be found in the HAZMAT Shipping Safety Guide | USPS Delivers.

Notes:

  • This table identifies the mailability of hazardous materials for domestic mail only.
  • Almost no hazardous materials are permitted in international mail.

The Hazardous Materials Table also lists the hazard class of a hazardous material. The mailability of hazardous materials by hazard class is further summarized for postal purposes by the "DOT Hazard Classes and Postal Mailability" table.

If you are a commercial mailer and have questions about the mailability of an item, contact the Mailing & Shipping Solutions Center for Mailing Requirements.

If a person knowingly mails items or materials that are dangerous or injurious to life, health, or property, they may face a civil penalty of at least $250, but not more than $100,000 per violation, the costs of any cleanup associated with each violation, and damages. They may also face criminal penalties.

 

Items possibly containing hazardous materials

Hazardous materials include any matter having a clear potential for causing harm to the mail, persons, or property involved in moving the mail. However, many commonly used items contain materials that are considered hazardous by U.S. Postal Service standards. Some fuel-containing items commonly found in the mail are:

  • Chainsaws
  • Lawn trimmers and edgers
  • Small motors and engines
  • Used fuel tanks (motorcycles, lawn mowers)
  • Small generators
  • Camp stoves
  • Gas lanterns or lamps
  • Model cars or aircraft

Each of the items listed is potentially mailable but only under one of the following conditions:

  • The item has never contained fuel, or
  • The fuel and all vapors have been completely purged from the item.

    Note:  If the item emits a fuel odor or if any residue is present on the outside or inside of the item, then the item is not completely purged.

Items containing fuel or fuel vapors are not mailable under any circumstances. Simply removing the fuel from an item does not make the item acceptable for mailing. Fuel tanks containing only vapors can have a greater explosion risk and thus become more hazardous than tanks that are full or partially full of fuel. The fuel must be removed and all vapors must be purged to allow these items to be safely mailed.
 

Presenting parcels and/or potentially hazardous materials to the Post Office™

  • At acceptance, Postal employees will ask, “Does this parcel contain anything liquid, fragile, perishable, or potentially hazardous?”
  • Postal employees will look out for parcels with items that could potentially contain fuel and advise mailers of the mailing limitations.
  • When accepting parcels, Postal employees will look for oil or fuel stains on the outside and fuel or petroleum odors.
  • If a mailpiece has markings denoting a flammable or combustible material, Postal employees will verify the contents with the mailer and with available references that all mailability requirements have been met.
  • While handling parcels, if Postal employees encounter a fuel odor, find liquid stains, or hear liquid sounds, they will move the parcel to the HAZMAT storage area or notify their supervisor.

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Items containing mercury or explosives

Can I mail explosives?
No, you can't mail explosives. All explosives, including fireworks, live ammunition, or gun powder, are completely prohibited in the mailstream. 
 

The following videos are available on explosives in the mail on the USPS TV YouTube channel:


Can I mail items containing mercury?

No, you can’t mail metallic mercury. Metallic mercury, which is a liquid at room temperature, and devices containing metallic mercury are always prohibited in the mailstream. This includes antique items such as mercury thermometers, mercury barometers, mercury blood pressure monitors and similar devices.

Compact fluorescent lamps (CFLs), which contain small amounts of mercury in vapor form, are mailable domestically, but not internationally. The mercury contained in CFLs and other devices like fluorescent tubes and similar consumer devices generally exists in a vaporized state and will never be visible to the naked eye.

See the 1-minute video on mailing mercury on the USPS TV YouTube channel.


Common Items Containing Mercury

Drops of liquid mercury (silver in color) poured from a clear, narrow vial on a black surface Liquid mercury:
Often encountered in a wide range of volumes. Reasons for sending include uses for gold reclamation/refinement, preparation of dental amalgams, and element collections.

Mailability
International:
Domestic Ground:
Domestic Air:
Prohibited
Prohibited
Prohibited

Prohibited as per Hazardous, Restricted, and Perishable Mail (Publication 52) Section 348.21e.

A barometer with mercury, a silver liquid, contained in a glass column located in the center of the barometer. Mercury barometer:
These devices often contain significant amounts of mercury that are not well contained. They have been responsible for several leaks.
Note: Fully digital versions are mailable without restrictions.

Mailability
International:
Domestic Ground:
Domestic Air:
Prohibited
Prohibited
Prohibited

Prohibited as per Hazardous, Restricted, and Perishable Mail (Publication 52) Section 348.21e.

A glass thermometer is broken in the middle with drops of its content, liquid mercury, spilled out. The mercury is silver is in color. Mercury thermometer:
These items may contain significant amounts of mercury in breakable containment (glass).
Note: Modern versions (i.e., digital and those using red liquid, which is alcohol to which red coloring has been added) are mailable without restrictions.

Mailability
International:
Domestic Ground:
Domestic Air:
Prohibited
Prohibited
Prohibited

Prohibited as per Hazardous, Restricted, and Perishable Mail (Publication 52) Section 348.21e.

This mercury blood pressure gauge consists of a cuff, a bulb for inflating and deflating the cuff, and a manometer. The manometer has an upright column of glass that contains liquid mercury. Mercury sphygmomanometer (blood pressure gauge):
These devices may contain significant amounts of mercury in breakable containment (glass).
Note: Fully digital versions are mailable without restrictions.

Mailability
International:
Domestic Ground:
Domestic Air:
Prohibited
Prohibited
Prohibited

Prohibited as per Hazardous, Restricted, and Perishable Mail (Publication 52) Section 348.21e.

Part of an image of a mercury switch. The switch in the image is a small, clear container with a drop of liquid mercury and two metal electrodes nearby. Note that the image was flipped 90 degrees counter clockwise. Mercury switch:
May exist in a small enough size to get below the 100 mg. limit; however, this would be the exception rather than the rule. If you can see the mercury, it is not mailable.

Mailability
International:
Domestic Ground:
Domestic Air:
Prohibited
Prohibited
Prohibited

Prohibited as per Hazardous, Restricted, and Perishable Mail (Publication 52) Section 348.21e, may encounter some that adhere to Section 348.22g.

Normally closed mercury relay, with coil around top of tube and adjustable angle. A pool of mercury fills the lower portion of the tube. Mercury relay:
May exist in a small enough size to get below the 100mg. limit; however, this would be the exception rather than the rule. If you can see the mercury, it is not mailable.

Mailability
International:
Domestic Ground:
Domestic Air:
Prohibited
Prohibited
Prohibited

Prohibited as per Hazardous, Restricted, and Perishable Mail (Publication 52) Section 348.21e, may encounter some that adhere to Section 348.22g.

A bulb that with a series of folded and curved tubes containing mercury in a gaseous form. Compact fluorescent lamps:
These items contain small amounts of mercury vapor. If broken, there will be no visible mercury and the vapors will readily disperse.

Mailability
International (includes APO/FPO/DPO addresses):
Domestic Ground:
Domestic Air:
Prohibited
Mailable
Mailable

See Hazardous, Restricted, and Perishable Mail (Publication 52) Packaging Instruction 8C for additional information.

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TitleWhat Does USPS® Classify as Hazardous Materials?
URL NameWhat-Does-USPS-Classify-as-Hazardous-Materials

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