A fire and gas detector occurs in four distinct phases. In the first, or incipient, phase, warming causes the emission of invisible but detectable gases. In the second phase, smoldering, smoke is formed, so smoke detectors can be used. In the third phase, when the ignition temperature has been reached, flames are present and therefore their emitted radiation (infrared [IR] and ultraviolet [UV]) can be detected. In the fourth and last stage of the fire, heat is released; the temperature of the space starts to rise.
There are three types of gas detection technologies
Fixed Point Gas Detectors
Open Path Gas Detectors
Ultrasonic Gas Leak Detectors
Point gas detector working principle is Infra-red (IR) gas detection is based on the absorption of energy by hydrocarbons. The bond between hydrogen and carbon absorbs proton energy at a wavelength of 3.3 µm .
A beam of IR energy is emitted between a source and detector and any attenuation caused by hydrocarbons in the short beam being electronically processed to give a reading in LEL (Lower Explosive Limit).
Open Path Gas Detectors (OPGD) are line-of-sight gas monitors commonly installed to monitor for gas presence over long distances. The wide-area coverage offered by Open Path Gas Detectors make them excellent instruments for perimeter and cross-sectional monitoring around storage tanks, off-shore platforms, along loading docks, and fence-line monitoring. Open Path Gas Detectors provide a high speed of response, they operate in extreme conditions, and require fewer instruments to monitor large areas. nfra-red (IR) gas detection is based on the absorption of energy by hydrocarbons.
The Incus Ultrasonic Gas Leak Detector is specifically designed to detect gas leaks at the speed of sound while providing wide area coverage. The technology works by responding to the acoustic noise created by a pressurized gas leak. Common high-pressure applications include air cooled heat exchangers, compressor stations, generators, gas metering skids, well bay areas, and separators.
Flammable Detection
Flammable Detection two Types
- Catalytic Gas Detectors
- Infrared Gas Detectors
Flame detectors alarm at the presence of light from flames, usually in the ultraviolet or infrared range. The detectors are set to detect the light flicker of a flame.
Electrochemical sensors are used for detecting oxygen and toxic gases. More pecifically, they measure the concentration of a specific gas within an external circuit. This is done by method of oxidation or reduction reactions. These reactions generate the positive or negative current flow through said external circuit. An electrochemical sensor is made up of a “working” electrode, a “counter” electrode, and usually a “reference” electrode.
Semiconductor sensors, also known as metal-oxide-semiconductor sensors (MOS sensors), detect gases by a chemical reaction that takes place when the gas comes in direct contact with the sensor. Tin dioxide is the most common material used in semiconductor sensors, and the electrical resistance in the sensor is decreased when it comes in contact with the monitored gas.