Intoduction to Smoke Alarms
Smoke alarms are one of the best lines of defense in your home. Thousands of lives every year are saved when a smoke alarm warns of a fire inside the home. While the safety aspect of the smoke alarm is certainly common knowledge, what may not be is how these devices work. There are two basic types of smoke alarms, and each one has a different method for detecting smoke, though both work on the same basic principle. In all smoke alarms, there is a detection device that could be something as simple as a beam of light, and when this device is interrupted by smoke, a signal is sent to the actual alarm inside and a loud ringing or beeping is made. This sound varies by alarm, but they all do the same thing: warn people of smoke and of a possible fire in their home. The types of smoke alarms most commonly seen in the home are ionization and photoelectric detectors.
Ionization Smoke Alarms
Ionization smoke alarms work with a small source of radioactive material known as americium-241. While the radioactive material is small, it has still been the source of controversy in the past regarding health. However, unless handled directly, the amount of americium-241 is too small to cause health risks. The smoke detector works with a battery and two small plates separated by only about a centimeter. The battery charges these plates, one with a positive charge and the other with a negative charge. The americium-241 releases particles that knock out electrons from particles in the air, therefore ionizing the space between the plates. As a result, the opposing plates attract electrons and neutrons and create a small current of electricity between them. When smoke enters the chamber, small particles attach themselves to the ions there and disrupt the current. When this happens, the alarm goes off.
Photoelectric Smoke Alarms
Photoelectric smoke alarms work differently and involve no radioactive elements. Instead, they concentrate on the way smoke is able to scatter and disrupt a beam of light. Inside these alarms, a small beam of light is emitted by an LED and shone horizontally over a small photoreceptor that will respond to light. The beam of light remains steady until smoke enters the alarm. When this happens, the light will hit the smoke and reflect off its particles, scattering the light in different directions. This will cause some of the light to hit the photoreceptor, which will in turn sound the alarm.
Tags: beam light, alarms work, radioactive material, smoke alarms, smoke alarms work
