A smoke detector can be described as a device that can sense the presence of smoke in a building
. It then issues a warning to the occupants to evacuate the building otherwise they would succumb to burns or to smoke inhalations. For the purpose of residential use two types of smoke detectors are being manufactured.
The first type is the photoelectric smoke detector that makes use of an optical beam that searches for smoke. It is when the smoke particles cover the beam that the photoelectric cell becomes aware of the decrease in light intensity and it triggers off an alarm. This kind of detector reacts very fast to smoldering fires which release huge amounts of smoke.
The second kind of smoke detector is the ionization chamber smoke detector or the ICSD. This is quick in sensing the flaming fires which produce little smoke. It makes use of a radioactive material that ionizes the air in a sensing chamber. It is the presence of smoke that affects the ion flow between a pair of electrodes and this triggers an alarm. Around 80% to 90% of the homes in America use this type of smoke detector.
How does ICSD operate?
The radiation from ICSD emits alpha particles which strip the electrons from the air molecules. This creates oxygen and nitrogen ions. While processing the electrons get attached to other air molecules. This forms negative oxygen and nitrogen ions. The two oppositely charged electrodes that exist within the sensing chamber attract the positive and negative ions. This sets up a small flow of current in the air space between the electrodes. It is when the smoke particles enter the chamber that they attract some of the ions. The current flow gets disrupted. The smoke detector keeps comparing the current flow in the sensing chamber with the current flow in the reference chamber. If there develops a massive difference an alarm gets triggered off.