Smoke extraction system design : smoke detectors
SMOKE EXTRACTION SYSTEM DESIGN : SMOKE DETECTORS
Smoke detector is a device which is used to detect the smoke when a fire occurs in the space where it is installed. There are two types of smoke detector i) ionization smoke detector ii) photoelectric smoke detector. The ionization smoke detector detect the fire more readily and swiftly. Photoelectric smoke detector detect the smoke without flame better and it is expensive.
The ionization smoke detector work on the principle of electric current flow method.The are two chamber which are present in this ionization smoke detector, When fire occurs some of the ions in the chamber gets attached to the smoke particle so it is unable to maintain the potential difference due to this there is a current difference which causes the smoke detector to sound. The ionization smoke detector detect incipient stage fire with invisible small particle. Ionization smoke detector respond faster in the flaming stages of fire, the smoke particle at this stage is made up of microscopic combustion particle.
The photoelectric smoke detector contains a light source a lens and an receiver. The light source will be either infrared or ultraviolet, A wall mounted unit emits a beam of light which is either processed or reflected by the reflector. When there is smoke the intensity of light which is processed or reflected will be less. If the light reflected or processed is less than the specified threshold value then the detector begins to alarm. The photo detector alarm respond fast to fire i.e at the smouldering stage itself(before the flame breaks). The smoke from this stage of fire is made up of large combustion particle.
Carbon dioxide sensor can also be used as a fire alarm because high level of CO2 may indicate fire, which is the fastest fire indicator as they can detect fire which do not produce smoke like hydrocarbon. The advantage of using CO2 sensor is it can be implemented in dusty environment.Thereby using smoke alarm large amount of life are saved and the injuries are prevented.