Pricing & Classification DMM Advisory

Message board to keep postal customers informed of changes to mailing standards, services, and prices.

June 21, 2024

Mercury Remains Prohibited in The Mail

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, switches and relays. However, compact fluorescent lamps, which contain small amounts of mercury in vapor form, are mailable domestically but not internationally (including APO/FPO/DPO destinations).

Due to the nature of mercury and its capability of producing toxic effects when inhaled or exposed to the skin, mercury represents a tremendous safety risk to our employees and customers.

When mercury spills it breaks into droplets and the droplets spread and build up in tiny cracks and spaces. It can absorb or be drawn into carpet, furniture, floors, walls and other items and be tracked throughout buildings and vehicles if not cleaned up right away. When spilled, it can vaporize (evaporate) into the air and get into the ventilation system ultimately spreading throughout buildings and vehicles. The vapor is very dangerous because it cannot be seen or smelled. If the spill occurs in a hot location (vehicle cargo area), it will vaporize more quickly and can be more dangerous.

Short-term exposure to high levels of mercury vapors include:

  • Headache
  • Cough, sore throat
  • Eye irritation
  • Vision problems
  • Chest pain
  • Increase in blood pressure or heart rate
  • Nausea, vomiting, diarrhea

Health effects caused by long-term exposure to mercury vapors include:

  • Anxiety
  • Tremors
  • Forgetfulness
  • Changes in hearing
  • Excessive shyness
  • Anorexia
  • Irritability
  • Sleeping problems
  • Loss of appetite
  • Changes in vision

It is for these reasons that elemental mercury is prohibited from the mail (Reference Publication 52, Hazardous, Restricted, and Perishable Mail (Pub 52) Section 348.21 and Appendix A.)  

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.

The Postal Service is committed to the safety and security of its employees, its customers, and its transportation networks.We must remain vigilant in safeguarding the mail stream against any article that might pose a hazard to health, safety, property, or the environment.

The Postal Service offers FAQs on prohibited items containing mercury and the Postal Inspection Service has released a public service announcement on mercury in the mail. Additionally, please see the chart below regarding information on commonly encountered mercury.


Commonly Encountered Mercury


Description of Item

Mailability of Item

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.

Domestic Ground – Prohibited
Domestic Air – Prohibited
International – Prohibited

Prohibited as per Section 348.21e

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.)

Domestic Ground – Prohibited
Domestic Air – Prohibited
International – Prohibited

Prohibited as per Section 348.21e

Mercury thermometer — These items may contain significant amounts of mercury in breakable containment (glass).

[Modern versions (i.e., digital and those using red liquid, which is alcohol to which red coloring has been added) are mailable without restrictions.]

Domestic Ground – Prohibited
Domestic Air – Prohibited
International – Prohibited

Prohibited as per Section 348.21e

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.)

Domestic Ground – Prohibited
Domestic Air – Prohibited
International – Prohibited

Prohibited as per Section 348.21e

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.

Domestic Ground – Prohibited
Domestic Air – Prohibited
International – Prohibited

Prohibited as per Section 348.21e, may encounter some that adhere to Section 348.22g

Mercury relay — 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.

Domestic Ground – Prohibited
Domestic Air – Prohibited
International – Prohibited

Prohibited as per Section 348.21e, may encounter some that adhere to Section 348.22g.

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.

Domestic Ground – Mailable
Domestic Air – Mailable
International – Prohibited

Mailable as per Section 348.22g.
See also Packaging Instruction 8C.