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Wednesday, April 24, 2019

Discuss the various types of smoke detectors


A smoke detector is a device which indicates a fire. Smoke detectors are very helpful in homes, offices, schools and industries. The smoke detector camera is a handy device because the harm caused by fire accidents is unbearable. Nowadays, the cost of smoke detectors and smoke alarms is very less because their use is growing and the manufacturing cost is declining.


Various types of smoke detectors:- There are five types of smoke detectors.

• Photoelectric smoke detector
• Smoke detector by ionisation
• Projected beam smoke detector
• Smoke detector aspirant
• Smoke detection video

Photoelectric smoke detector:- A pulsed light beam from a light emitting diode (LED) with its connected optics is predictable through the interior of a blackened chamber that could contain smoke to be detected. A photocell, through its optics, looks at the beam projected next to a line perpendicular to the beam. When the smoke enters into the chamber, the smoke particles are reflecting in a small part of the beam of light near the photocell, which provides a voltage that is amplified and causes an alert. The light source is observed in front of the smoke chamber and synchronised to stop the discrepancy of the intensity of the light and create erratic operation of the detector.

    Smoke detector by ionisation:- A small amount of radioactive material ionises the air inside a chamber that releases the ambient air. It allows a little amount of calculated electric current to flow via the ionised air. Some small products of solid particles of combustion that enter the chamber, as an output of the fire, interfere with the constant movement of the ions (current) and when the current lowers, the alarm sounds.

    Projected beam smoke detector:- The projected beam smoke detector works according to the principle of darkening of the light and contains a transmitter and projected beam lens, the light receiver and the light reflector (not in all cases). The light emitter emits an invisible beam of light that receives a recipient under normal conditions. The receiver is calibrated to stand for the sensitivity level based on a percentage of total dimming. When the smoke obscures the beam, an alarm signal is turned on.

    Aspirating smoke detector:- An aspiration smoke detector is a sensitive light sensor or nephelometer, which works by dynamically extracting an air sample and added contaminants through a network of pipes to a detection chamber. It consists of the following main components: a system of small diameter pipes, particle filter, a detection chamber, focused light source and also a sensitive light recipient. When the smoke enters the detection chamber via the path of the light beam, the light is scattered or hidden by the smoke particles, which is identified by the sensor.

    Video smoke detection:- Video smoke detection (VSD) based on a computerised analysis of video images given by standard video cameras (CCTV). A video smoke detection system consists of the following parts: more than one video cameras, computer and software to examine the video signal. The computer uses specific software to recognise the individual movement and smoke pattern. This unique signal identifies activated an alarm.

Smoke alarms also vary in the way they are available. In the market various wireless smoke detectors are available, but battery-powered smoke alarms are accessible due to t low cost.

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