Nuclear Chemistry- The Science Behind Smoke Alarms

The Science Behind Smoke Alarms

Smoke alarms are an item found in many common households that rarely get any attention, except for when their batteries need to be changed. There are many different types of smoke alarms, such as photoelectric detectors and ionization detectors. It is interesting that all of these smoke alarms have an interesting way of functioning that involves chemistry.
Most smoke detectors use americium-241, which is a common source of alpha radiation, to detect whether there is smoke in the area. The alpha radiation ionizes the air particles inside the smoke detector, causing an electric current. If any smoke enters the detector, the alpha radiation particles are forced to reduce the ionization of the air particles, causing the electric current to decrease. This is detected by the smoke alarm, causing the alarm to sound.
The photoelectric detector works differently from the ionization detector, in that it uses a photo beam detector to detect smoke. However, it would only be useful when the smoke is thick enough to block out light, as it is not very sensitive.
The ionization detector, on the other hand, is much more efficient because not only is it more sensitive to smoke, it uses the air particles as opposed to light, to detect smoke or a fire in a room.






Sources:
http://www.bbc.co.uk/schools/gcsebitesize/science/add_ocr_gateway/radiation/radioisotopesrev3.shtml
http://home.howstuffworks.com/home-improvement/household-safety/fire/smoke.htm