Am is chemical symbol of Americium. Whereas 95 is the atomic number of it with 243.0 automic mass units. It also belongs to the fourth synthetic transuranic element. Besides, Actinides is a group of metal elements of it and Rare Earth Metal is a family of Americium.

Radiation Facts

  • Americium(IV) is stable in concentrated H3 PO 4, K 4 P 2 O 7, phosphotungstate, and fluoride (NH 4 F, KF) solutions, and is otherwise reduced to Am III.
  • Americium is a particularly high alpha and gamma ray emitter. It is used in gamma-ray imaging equipment and as an ionization source in smoke detectors. The most stable isotope of americium has a half-life of 7,370 years. Biological Benefits. Americium has no biological use.
  • Americium-241 (241Am, Am-241) is an isotope of americium. Like all isotopes of americium, it is radioactive, with a half-life of 432.2 years. 241 Am is the most common isotope of americium as well as the most prevalent isotope of americium in nuclear waste.
  • Some smoke detectors use very small amounts of radioactive material to detect smoke.
  • While they are safe to use in your home, never tamper with an ionization smoke detector.
  • Replace the batteries in your smoke detectors every year.

Smoke detectors are common household items that keep you and your family safe by alerting you to smoke in your home. Ionization smoke detectors use a small amount of radioactive material, americium-241, to detect smoke.

About Americium in Ionization Smoke Detectors

A woman installs a smoke detector in her home.
Source: Federal Emergency Management Agency (FEMA)

Ionization smoke detectors use americium as a source of alpha particles. Alpha particles from the americium source ionize air molecules. This makes some particles positively charged and some negatively charged. Two charged plates inside of the ionization smoke detector create a flow of positively and negatively charged ions. The smoke alarm triggers when smoke breaks the constant flow of ions.

Alpha particles are very heavy and cannot travel very far. They can be shielded by a layer as thin as a layer of dead skin cells. Ionization smoke detectors have a small americium source encased in a layer of foil and ceramic, which stops the alpha particles from traveling outside of the smoke detector. Because of this shielding, the smoke detector poses no radiation health risk when they are properly handled.

There is no health threat from ionization smoke detectors as long as the detector is not damaged and used as directed. Do not tamper with your smoke detectors, as it could damage the shielding around the radioactive source inside of them. There are no special disposal instructions for ionization smoke detectors. They may be thrown away with household garbage, or your community may have a separate recycling program.

This diagram shows how an americium source ionizes air particles and makes an ionization smoke detector work.

What You Can Do

  • Use a smoke detector in your home. It can save your life.
  • Never tamper with an ionization smoke detector. Never attempt to tamper with or remove the americium.
  • Replace the batteries. Replace the batteries in every smoke detector in your home twice a year. Most detectors are certified for a useful life of ten years. Check the expiration date on your smoke detector when you replace the batteries.
  • Throw away outdated ionization smoke detectors. Your community may have a separate recycling program for them.

Where to Learn More

The States

Each state has a program to protect people from radiation exposure. They control the use and disposal of radioactive material in consumer products.

Radiation Control Programs Exit
The Conference of Radiation Control Program Directors (CRCPD)
This webpage provides links and contact information for each state's Radiation Control Program office.

The U.S. Nuclear Regulatory Commission (NRC)

Americium facts for kids

Adobe character animator free. Licenses are required for anyone who sells, uses, or disposes of radioactive material. The NRC sets rules for obtaining these licenses. Companies that make ionization smoke detectors must have a license. However, people who purchase the smoke detectors for their homes do not need a license.

Fact sheet on Smoke Detectors
This webpage discusses the history of ionization chamber smoke detectors and describes how they work.

The U.S. Environmental Protection Agency (EPA)

The EPA protects human health and the environment from unnecessary exposure to ionizing radiation. This includes public education and materials related to radionuclides, like the ones that are used in ionization smoke detectors.

Radionuclides Basics: Americium-241
This webpage provides basic scientific information on americium as well as information on human exposure, health effects, and protecting people from radiation.

Americium Facts

The U.S. Department of Homeland Security (DHS), the Federal Emergency Management Agency (FEMA), the U.S. Fire Administration


The U.S. Fire Administration works to foster a solid foundation for national, state, and local organizations that prevent, prepare, and respond to fires.

Smoke Alarm Outreach
This webpage includes infographics, frequently asked questions, and good information about smoke alarm effectiveness and importance.

Americium in the Environment

Am-241 found in the environment is in the form of microscopic dust.

  • When released into air, americium deposits particles in the soil and water. Small particles in air can travel far from the release site.
  • In water, americium will stick to particles in the water or to the sediment at the bottom.
  • Deposited on soil, americium will stick to surface particles, but not go very deep into the ground.
  • Plants and vegetation growing in or nearby contaminated soil may take up small amounts of americium from the soil.

Americium Sources

Exposure to any significant amount of Am-241 is unlikely under normal circumstances. Small amounts of it are found in the soil, plants and water from nuclear weapons testing.

Some smoke detectors contain very small amounts of Am-241. There is no health risk from americium in smoke detectors as long as the detector is not tampered with and is used as directed. When disposing of a smoke detector, follow manufacturer instructions or check with your local fire department for instructions.


Americium and Health

Am-241 is primarily an alpha emitter, but also emits some gamma rays. It poses a more significant risk if ingested (swallowed) or inhaled. Once in the body, it tends to concentrate in the bone, liver, and muscle. Americium can stay in the body for decades and continue to expose the surrounding tissues to radiation, increasing the risk of developing cancer.