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'{{merge from|Gas leak detection|date=December 2013}} [[Image:Detector for Gas.jpg|thumb|250px|right|Portable gas detector]] A '''gas detector''' is a device which detects the presence of various [[gas]]es within an area, usually as part of a safety system. This type of equipment is used to detect a gas leak and interface with a control system so a process can be automatically shut down. A gas detector can also sound an alarm to operators in the area where the leak is occurring, giving them the opportunity to leave the area. This type of device is important because there are many gases that can be harmful to organic life, such as humans or animals. Gas detectors can be used to detect [[combustible]], [[flammable]] and [[toxic]] gases, and [[oxygen]] depletion. This type of device is used widely in industry and can be found in a variety of locations such as on oil rigs, to monitor manufacture processes and emerging technologies such as [[photovoltaic]].They may also be used in [[firefighting]]. Gas detectors are usually battery operated. They transmit warnings via a series of audible and visible signals such as alarms and flashing lights, when dangerous levels of gas vapors are detected. As detectors measure a gas concentration, the sensor responds to a calibration gas, which serves as the reference point or scale. As a sensor’s detection exceeds a preset alarm level, the alarm or signal will be activated. As units, gas detectors are produced as portable or stationary devices. Originally, detectors were produced to detect a single gas, but modern units may detect several toxic or combustible gases, or even a combination of both types.<ref>[http://www.thomasnet.com/articles/instruments-controls/How-Gas-Detectors-Work How Gas Detectors Work]</ref> The European Community has supported a research called the MINIGAS project that was coordinated by VTT Technical Research Center of Finland.<ref name=Optics29Jan2013> Matthew Peach, Optics.org. "[http://optics.org/news/4/1/43 Photonics-based MINIGAS project yields better gas detectors]." Jan 29, 2013. Retrieved Feb 15, 2013. </ref> This research project aims to develop new types of photonics-based gas sensors, and to support the creation of smaller instruments with equal or higher speed and sensitivity than conventional laboratory-grade gas detectors.<ref name=Optics29Jan2013/> == Types == Gas detectors can be classified according to the operation mechanism (semiconductors, oxidation, catalytic, infrared, etc.).Gas detectors come in two main types: portable devices and fixed gas detectors. The first is used to monitor the atmosphere around personnel and is worn on clothing or on a belt/harness. The second type of gas detectors are fixed type which may be used for detection of one or more gas types. Fixed type detectors are generally mounted near the process area of a plant or control room. Generally, they are installed on fixed type mild steel structures and a cable connects the detectors to a [[SCADA]] system for continuous monitoring and where a tripping interlock can be activated for an emergency situation. Newer gas analyzers can break up the component signals in a complicated aroma to identify several gasses simultaneously.<ref>{{cite journal|last=Wali|first=Russeen|title=An electronic nose to differentiate aromatic flowers using a real-time information-rich piezoelectric resonance measurement|journal=Procedia Chemistry|date=2012|year=2012|doi=10.1016/j.proche.2012.10.146}}</ref> == Gas detector calibration == All gas detectors must be [[calibrated]] on a schedule. Of the two types of gas detectors, portables must be calibrated more frequently due to the regular changes in environment they experience. A typical calibration schedule for a fixed system may be quarterly, bi-annually or even annually with some of the more robust units. A typical calibration schedule for a portable gas detector is a daily bump test accompanied by a monthly calibration.<ref>{{cite web|last=Moore|first=James|url=http://www.idealcalibrations.com/gas-detector-news/2010/10/14/article-calibration-who-needs-it-by-james-moore-occupational.html|title=Calibration: Who Needs It?|publisher=Occupational Health and Safety Magazine}}</ref> Almost every portable gas detector out there has a specific [[calibration gas]] requirement which is available from the manufacturer you purchased your monitor from. == Gas detector challenge [bump] test == As a gas detector is used for employee/worker safety it is very important to make sure it is operating to manufacturer's specifications. Australian standards specify that a person operating any gas detector is strongly advised to check the gas detectors performance each day and that it is maintained and used in accordance with the manufacturers instructions and warnings.<ref>{{cite web|last=Colhoun|first=Jacquie|url=http://http://www.aegissafety.com.au/index.php/gas-detection-blog/87-products/gas-detection/260-challenge-testing-your-gas-detector.html|title=Who is responsible for bump/challenge testing your gas detector}}</ref> A challenge test should consist of exposing the gas detector to a know concentration of gas to ensure that the gas detector will respond and that both the audible and visual alarms activate. It is also important inspect the gas detector for any accidental or deliberate damage by checking that the housing and screws are all intact to prevent any liquid ingress and that the filter is clean, all of which can effect the functionality of the gas detector. The basic calibration or challenge test kit will consist of: [[Calibration Gas]] / Regulator / Calibration Cap and hose [these are generally supplied with the gas detector at time of purchase] and a case for storage and transport. Many a large business will utilise an automated test/calibration station for use to bump test and calibrate their gas detectors. == Oxygen concentration == Oxygen deficiency gas monitors are used for employee and workforce safety. [[Cryogenics|Cryogenic]] substances such as [[liquid nitrogen]] (LN2), liquid [[helium]] (He), and liquid [[argon]] (Ar) are inert and can displace oxygen (O₂) in a confined space if a leak is present. A rapid decrease of oxygen can provide a very dangerous environment for employees. With this in mind, an oxygen gas monitor is important to have when cryogenics are present. Laboratories, [[Magnetic resonance imaging|MRI]] rooms, pharmaceutical, semiconductor, and cryogenic suppliers are typical users of oxygen monitors. Oxygen fraction in a breathing gas is measured by [[electro-galvanic fuel cell]] sensors. They may be used stand-alone, for example to determine the proportion of oxygen in a [[nitrox]] mixture used in [[scuba diving]],<ref name=DANnitrox>{{cite book |title=DAN Nitrox Workshop Proceedings |author=Lang, M.A. |year=2001 |publisher=Divers Alert Network |location=Durham, NC |page=197 |url=http://archive.rubicon-foundation.org/4855 |accessdate=2009-03-20 }}</ref> or as part of feedback loop which maintains a constant [[partial pressure]] of oxygen in a [[rebreather]].<ref name=Goble>{{cite journal |author=Goble, Steve |title=Rebreathers |journal=[[South Pacific Underwater Medicine Society]] Journal |volume=33 |issue=2 |year=2003 |pages=98–102 |url=http://archive.rubicon-foundation.org/7782 |accessdate=2009-03-20 }}</ref> ==Hydrocarbons and VOCs== {{further2|[[Volatile organic compound#VOC Sensors]]}} Detection of hydrocarbons can be based on the mixing properties of gaseous hydrocarbons – or other [[volatile organic compound]]s (VOCs) – and the sensing material incorporated in the sensor. The selectivity and sensitivity depends on the molecular structure of the VOC and the concentration; however it is difficult to design a selective sensor for a single VOC. Many VOC sensors detect using a fuel-cell technique. VOCs in the environment or certain atmospheres can be detected based on different principles and interactions between the organic compounds and the sensor components. There are electronic devices that can detect ppm concentrations despite not being particularly selective. Others can predict with reasonable accuracy the molecular structure of the volatile organic compounds in the environment or enclosed atmospheres<ref>{{cite journal |doi=10.1021/la102693m |title=Holographic Detection of Hydrocarbon Gases and Other Volatile Organic Compounds |year=2010 |last1=MartíNez-Hurtado |first1=J. L. |last2=Davidson |first2=C. A. B. |last3=Blyth |first3=J. |last4=Lowe |first4=C. R. |journal=Langmuir |volume=26 |issue=19 |pages=15694–9 |pmid=20836549}}</ref> and could be used as accurate monitors of the Chemical Fingerprint and further as health monitoring devices. [[Solid-phase microextraction]](SPME)techniques are used to collect VOCs at low concentrations for analysis.<ref>{{cite journal |doi=10.1016/j.chroma.2003.11.069 |title=Identification of volatile organic compounds emitted by a naturally aged book using solid-phase microextraction/gas chromatography/mass spectrometry |year=2004 |last1=Lattuati-Derieux |first1=Agnès |last2=Bonnassies-Termes |first2=Sylvette |last3=Lavédrine |first3=Bertrand |journal=Journal of Chromatography A |volume=1026 |pages=9–18 |pmid=14870711 |issue=1–2}}</ref> ===Considerations for detection of hydrocarbon gases /risk control=== * Methane is lighter than air (possibility of accumulation under roofs) * Ethane is slightly heavier than air (possibility of pooling at ground levels / pits) * Propane is heavier than air (possibility of pooling at ground levels / pits) * Butane is heavier than air (possibility of pooling at ground levels / pits) ==Combustible== *[[Catalytic bead sensor]] *[[Explosimeter]] *[[Infrared point sensor]] *[[Infrared open path detector]] ==Other== *[[Flame ionization detector]] *[[Nondispersive infrared sensor]] *[[Photoionization detector]] *[[Zirconium oxide]] sensor cell *Catalytic sensors *[[Metal oxide semiconductor]] *Gold film *[[Colorimetric Detector Tubes]] *Sample collection and chemical analysis *Piezoelectric microcantilever *[[Holographic Sensor]] *[[Thermal Conductivity Detector]] *[[Electrochemical gas sensor]] == manufacturers == <!-- To avoid a link farm, please only add manufacturers who are notable enough to have a Wikipedia article --> * [http://www.crowcon.com/ Crowcon] * [[FIDEGAS - www.fidegas.com]] * [[Honeywell Analytics]] * Sensor Electronics Corporation * Riken Keiki * [http://www.sierramonitor.com/gas/about/Fire-Gas-Detection.php Sierra Monitor Corporation] * [[Dräger]] * [[Mine Safety Appliances]] * [[Industrial Scientific Corporation]] * [[UNIPHOS]] Envirotronic Pvt. Ltd. [http://www.uniphos.eu/ (link)] * [http://www.otisinstruments.com/ OTIS Instruments] ==See also== *[[Gas leak]] *[[Gas leak detection]] *[[Hydrogen sensor]] *[[List of sensors]] ==References== {{Reflist}} {{DEFAULTSORT:Gas Detector}} [[Category:Safety equipment]] [[Category:Detectors]] [[Category:Gas sensors]] [http://www.aesolutions.com.au/products/gas-fixed-detection.php Gas Detector Types]'