Americium smoke detector
Encyclopedia
An americium smoke detector is a smoke detector
that uses americium-241 to detect the changes in the flow of ions that indicates the presence of smoke. In a smoke detector that uses americium-241 to detect smoke contains an amount of elemental americium-241 that is so small that it does not harm the human body (cause cancer
or radiation sickness
).
As seen in the image to the right the americium is placed towards the edge of the smoke detector and is powered by a standard 9V battery. Since americium is only the third transuranic element it is relatively stable and can be placed in a smoke detector.
. This enables the smoke detector to be able to detect smoke while also not causing diseases among human beings who come into close vicinity to it on regular basis. The amount may be tiny but it is still required to be disposed of correctly. The presence of americium-241 means that every decommissioned smoke detector must be properly disposed of lest it constitute an environmental hazard.
Ionisation detectors are more sensitive to flaming fires than optical detectors, while optical detectors are more sensitive to smouldering fires.
americium-241 in the smoke detector emits ionizing radiation
into a chamber that is open to the air. The air molecule
s in the chamber become ionized and these ions allow the passage of a small electric current
between charged
electrode
s placed in the chamber. If any smoke particles pass into the chamber the ions will attach to the particles and so will be less able to carry the current. An electronic circuit detects the current drop, and sounds the alarm.
Smoke detector
A smoke detector is a device that detects smoke, typically as an indicator of fire. Commercial, industrial, and mass residential devices issue a signal to a fire alarm system, while household detectors, known as smoke alarms, generally issue a local audible and/or visual alarm from the detector...
that uses americium-241 to detect the changes in the flow of ions that indicates the presence of smoke. In a smoke detector that uses americium-241 to detect smoke contains an amount of elemental americium-241 that is so small that it does not harm the human body (cause cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
or radiation sickness
Radiation Sickness
Radiation Sickness is a VHS by the thrash metal band Nuclear Assault. The video is a recording of a concert at the Hammersmith Odeon, London in 1988. It was released in 1991...
).
As seen in the image to the right the americium is placed towards the edge of the smoke detector and is powered by a standard 9V battery. Since americium is only the third transuranic element it is relatively stable and can be placed in a smoke detector.
How much americium is used in one?
The amount of americium-241 used is less than 1 μgMicrogram
In the metric system, a microgram is a unit of mass equal to one millionth of a gram , or 1/1000 of a milligram. It is one of the smallest units of mass commonly used...
. This enables the smoke detector to be able to detect smoke while also not causing diseases among human beings who come into close vicinity to it on regular basis. The amount may be tiny but it is still required to be disposed of correctly. The presence of americium-241 means that every decommissioned smoke detector must be properly disposed of lest it constitute an environmental hazard.
The reason for using Americium-241
The radioactive element, americium-241, is used in smoke detectors despite the fact that there are other options available. The use of americium-241 is cheaper compared to other smoke detectors such as ones that look for smoke.Ionisation detectors are more sensitive to flaming fires than optical detectors, while optical detectors are more sensitive to smouldering fires.
How it works
The radioactive isotopeIsotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
americium-241 in the smoke detector emits ionizing radiation
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
into a chamber that is open to the air. The air molecule
Molecule
A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...
s in the chamber become ionized and these ions allow the passage of a small electric current
Electric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...
between charged
Electric charge
Electric charge is a physical property of matter that causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Two positively charged substances, or objects, experience a mutual repulsive force, as do two...
electrode
Electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit...
s placed in the chamber. If any smoke particles pass into the chamber the ions will attach to the particles and so will be less able to carry the current. An electronic circuit detects the current drop, and sounds the alarm.