they are bad
alpha radiation
Alpha radiation is emitted from the amercium button in a smoke detector. When smoke goes into the smoke detector it blocks the stream of alpha particles emitted from the americium. That triggers an alarm.
It is used in smoke detectors as it cannot travel far in air. Alpha radiation is emitted and as long as the detector in the device is receiving the alpha radiation, then no smoke is present. When smoke particles are present, they interrupt the radiation, and so the detector doesn't pick up the radiation, causing the alarm to go off.
Americium-241 this is an emitter of alpha radiation, which is used in smoke detectors as it is very ionising and will not be able to travel through smoke. Therefore, in a fire the detector will not receive any alpha radiation and hence the alarm will go off.
Alpha particles are useful in smoke detectors because they are easily absorbed by smoke particles. When this happens, the flow of electrical current between the electrodes, said flow being comprised of alpha particles, is reduced and causes the alarm to activate.
Most smoke alarms use Americium-241 to detect smoke and hot air, thus triggering the alarm. Some gamma radiation is emitted by the smoke alarm but all the alpha radiation is blocked by the black box. Living for a year within 1 metre of a smoke alarm would give you a radiation dose of 1.5 millimeters per year, which is about 1/1000th of the radiation that we receive normally. If you held a smoke alarm in your hand then you would get a significant dose, but you're not going to do that are you? The Americium is chosen because of it's very high melting point (it's designed to work in a fire). Even in a house fire, the material will not melt and would not be a health hazard. But there are some safety things to remember - Never hold a smoke alarm in your hand to long - Never attempt to disassemble the radioactive elements housing or damage it as will release radiation still capable of causing a health hazard
Alpha is used because it rarely effects our bodies from the outside. This is because it only travels approximately 5cm. Beta and Gamma are more dangerous as they can travel through your skin.
Alpha particles are used in various applications, including smoke detectors, nuclear power generation, and as a treatment for certain types of cancer. Their relatively large mass and high ionization ability make them effective for disrupting and destroying cancer cells in targeted radiation therapy.
There are two types of smoke detectors:Photoelectric Smoke detectorsIonizing Smoke DetectorsIonization smoke detectors are more commonly used. The smoke detector uses an ionization chamber and a source of ionizing radiation to detect smoke.Alpha particles are emitted from from the chamber, which ionize the air, so that the air conducts electricity and a small current flows.If smoke enters the alarm, it absorbs the alpha particles causing the current to reduce, and the alarm sounds.Generally, smoke detectors use a weak source made of Americium-241 (241Am95).Note: Alpha particles are the nuclei of a Helium Atom (4He2).
Smoke detectors use a small amount of radioactive material (usually americium-241) to emit alpha particles. When smoke enters the detector, it scatters the alpha particles, disrupting the electric current within the detector and setting off the alarm.
Alpha radiation from americium-241 is used in smoke detectors because it ionizes the air particles, causing a small electric current to flow and trigger the alarm. Gamma radiation from americium-241 can be used in radiography to detect flaws in materials or for sterilization purposes.
The fire alarm device is usually equipped with an Amercium-241 that is alpha emitter source together with a battery derived electric circuit. In the normal situation the alpha particles ionize the air causing circuit connection. However when there is a smoke the circuit is disconnected due to the smoke that acts as an insulator and hence the alarm is actuated.