Gas detector
A gas detector is a device that detects the presence of gases in an area, often as part of a safety system. A gas detector can sound an alarm to operators in the area where the leak is occurring, giving them the opportunity to leave. 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
Gas leak detection is the process of identifying potentially hazardous
History
Gas leak detection methods became a concern after the effects of harmful gases on human health were discovered. Before modern electronic
The first gas detector in the industrial age was the flame safety lamp (or Davy lamp) was invented by Sir Humphry Davy (of England) in 1815 to detect the presence of methane (firedamp) in underground coal mines. The flame safety lamp consisted of an oil flame adjusted to specific height in fresh air. To prevent ignition with these lamps the flame was contained within a glass sleeve with a mesh flame arrestor. The flames height varied depending on the presence of methane (higher) or the lack of oxygen (lower). To this day, in certain parts of the world flame safety lamps are still in service.
The modern era of gas detection started in 1926–1927 with the development of the catalytic combustion (LEL) sensor by Dr.Oliver Johnson. Dr Johnson was an employee of Standard Oil Company in California (now Chevron), he began research and development on a method to detect combustible mixtures in air to help prevent explosions in fuel storage tanks. A demonstration model was developed in 1926 and denoted as the Model A. The first practical "electric vapor indicator" meter begun production in 1927 with the release of the Model B.
The world's first gas detection company, Johnson-Williams Instruments (or J-W Instruments) was formed in 1928 in Palo Alto, CA by Dr Oliver Johnson and Phil Williams. J-W Instruments is recognized as the first electronics company in Silicon Valley. Over the next 40 years J-W Instruments pioneered many "firsts" in the modern age of gas detection, including making instruments smaller and more portable, development of a portable oxygen detector as well as the first combination instrument that could detect both combustible gases/vapors as well as oxygen.
Before the development of electronic household carbon monoxide detectors in the 1980s and 1990s, carbon monoxide presence was detected with a chemically infused paper that turned brown when exposed to the gas. Since then, many electronic technologies and devices have been developed to detect, monitor, and alert the leak of a wide array of gases.
As the cost and performance of electronic gas sensors improved, they have been incorporated into a wider range of systems. Their use in automobiles was initially for
Originally, detectors were produced to detect a single gas. Modern units may detect several toxic or combustible gases, or even a combination.[1] Newer gas analyzers can break up the component signals from a complex aroma to identify several gases simultaneously.[2]
Types
Gas detectors can be classified according to the operation mechanism (semiconductor, oxidation, catalytic, photoionization, infrared, etc.). Gas detectors come packaged into two main form factors: portable devices and fixed gas detectors.
Portable detectors are used to monitor the atmosphere around personnel and are either hand-held or worn on clothing or on a belt/harness. These gas detectors are usually battery operated. They transmit warnings via audible and visible signals, such as alarms and flashing lights, when dangerous levels of gas vapors are detected.
Fixed type gas detectors may be used for detection of one or more gas types. Fixed type detectors are generally mounted near the
Electrochemical
Electrochemical gas detectors work by allowing gases to diffuse through a porous membrane to an electrode where it is either chemically oxidized or reduced. The amount of current produced is determined by how much of the gas is oxidized at the electrode,[4] indicating the concentration of the gas. Manufactures can customize electrochemical gas detectors by changing the porous barrier to allow for the detection of a certain gas concentration range. Also, since the diffusion barrier is a physical/mechanical barrier, the detectors tend to be more stable and reliable over the sensor's duration and thus required less maintenance than other early detector technologies.
However, the sensors are subject to corrosive elements or chemical contamination and may last only 1–2 years before a replacement is required.[5] Electrochemical gas detectors are used in a wide variety of environments such as refineries, gas turbines, chemical plants, underground gas storage facilities, and more.
Catalytic bead
Catalytic bead (
Photoionization
Photoionization detectors (PIDs) use a high-photon-energy UV lamp to ionize chemicals in the sampled gas. If the compound has an ionization energy below that of the lamp photons, an electron will be ejected, and the resulting current is proportional to the concentration of the compound. Common lamp photon energies include 10.0 eV, 10.6 eV and 11.7 eV; the standard 10.6 eV lamp lasts for years, while the 11.7 eV lamp typically last only a few months and is used only when no other option is available. A broad range of compounds can be detected at levels ranging from a few parts per billion (ppb) to several thousand parts per million (ppm). Detectable compound classes in order of decreasing sensitivity include: aromatics and alkyl iodides; olefins, sulfur compounds, amines, ketones, ethers, alkyl bromides and silicate esters; organic esters, alcohols, aldehydes and alkanes; hydrogen sulfide, ammonia, phosphine and organic acids. There is no response to standard components of air or to mineral acids. Major advantages of PIDs are their excellent sensitivity and simplicity of use; the main limitation is that measurements are not compound-specific. Recently PIDs with pre-filter tubes have been introduced that enhance the specificity for such compounds as benzene or butadiene. Fixed, hand-held and miniature clothing-clipped PIDs are widely used for industrial hygiene, hazmat, and environmental monitoring.
Infrared point
Infrared (IR) point sensors use radiation passing through a known volume of gas; energy from the sensor beam is absorbed at certain wavelengths, depending on the properties of the specific gas. For example, carbon monoxide absorbs wavelengths of about 4.2-4.5 μm.[6] The energy in this wavelength is compared to a wavelength outside of the absorption range; the difference in energy between these two wavelengths is proportional to the concentration of gas present.[6]
This type of sensor is advantageous because it does not have to be placed into the gas to detect it and can be used for
. IR sensors are commonly found in waste-water treatment facilities, refineries, gas turbines, chemical plants, and other facilities where flammable gases are present and the possibility of an explosion exists. The remote sensing capability allows large volumes of space to be monitored.Engine emissions are another area where IR sensors are being researched. The sensor would detect high levels of carbon monoxide or other abnormal gases in vehicle exhaust and even be integrated with vehicle electronic systems to notify drivers.[6]
Infrared imaging
Infrared
Semiconductor
MOS sensors can detect different gases, such as carbon monoxide, sulfur dioxide, hydrogen sulfide, and ammonia. Since the 1990s, MOS sensors have become important environmental gas detectors.[3] MOS sensors although very versatile, suffer from the problem of cross sensitivity with humidity. The cause for such behaviour has been attributed to interaction of hydroxyl ions with the oxide surface.[12] Attempts have been made to reduce such interference using algorithmic optimizations.[13]
Ultrasonic
Ultrasonic gas detectors are mainly used for remote sensing in outdoor environments where weather conditions can easily dissipate escaping gas before allowing it to reach leak detectors that require contact with the gas to detect it and sound an alarm. These detectors are commonly found on offshore and onshore oil/gas platforms, gas compressor and metering stations, gas turbine power plants, and other facilities that house a lot of outdoor pipeline.
Holographic
Calibration
All gas detectors must be
Challenge (bump) test
Because 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 detector's performance each day and that it is maintained and used in accordance with the manufacturers instructions and warnings.[17]
A challenge test should consist of exposing the gas detector to a known concentration of gas to ensure that the gas detector will respond and that the audible and visual alarms activate. It is also important to inspect the gas detector for any accidental or deliberate damage by checking that the housing and screws are intact to prevent any liquid ingress and that the filter is clean, all of which can affect the functionality of the gas detector. The basic calibration or challenge test kit will consist of calibration gas/regulator/calibration cap and hose (generally supplied with the gas detector) and a case for storage and transport. Because 1 in every 2,500 untested instruments will fail to respond to a dangerous concentration of gas, many large businesses use an automated test/calibration station for bump tests and calibrate their gas detectors daily.[18]
Oxygen concentration
Oxygen deficiency gas monitors are used for employee and workforce safety. 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, who may not notice this problem before they suddenly lose consciousness. With this in mind, an oxygen gas monitor is important to have when cryogenics are present. Laboratories, MRI rooms, pharmaceutical, semiconductor, and cryogenic suppliers are typical users of oxygen monitors.
Oxygen fraction in a breathing gas is measured by electro-galvanic oxygen sensors. They may be used stand-alone, for example to determine the proportion of oxygen in a nitrox mixture used in scuba diving,[19] or as part of feedback loop which maintains a constant partial pressure of oxygen in a rebreather.[20]
Ammonia
Gaseous ammonia is continuously monitored in industrial refrigeration processes and biological degradation processes, including exhaled breath. Depending on the required sensitivity, different types of sensors are used (e.g., flame ionization detector, semiconductor, electrochemical, photonic membranes[21]). Detectors usually operate near the lower exposure limit of 25ppm;[22] however, ammonia detection for industrial safety requires continuous monitoring above the fatal exposure limit of 0.1%.[21]
Combustible
- Catalytic bead sensor
- Explosimeter
- Infrared point sensor
- Infrared open path detector
Other
- Flame ionization detector
- Nondispersive infrared sensor
- Photoionization detector
- Zirconium oxidesensor 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
Household safety
There are several different sensors that can be installed to detect hazardous gases in a residence. Carbon monoxide is a very dangerous, but odorless, colorless gas, making it difficult for humans to detect. Carbon monoxide detectors can be purchased for around US$20–60. Many local jurisdictions in the United States now require installation of carbon monoxide detectors in addition to smoke detectors in residences.
Handheld flammable gas detectors can be used to trace leaks from natural gas lines, propane tanks, butane tanks, or any other combustible gas. These sensors can be purchased for US$35–100.
Research
The European Community has supported research called the MINIGAS project that was coordinated by VTT Technical Research Center of Finland.[23] 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.[23]
See also
References
- ^ "How Gas Detectors Work".
- .
- ^ PMID 30424341.
- ^ Detcon, http://www.detcon.com/electrochemical01.htm Archived 2009-05-05 at the Wayback Machine
- ^ United States Patent 4141800: Electrochemical gas detector and method of using same, http://www.freepatentsonline.com/4141800.html
- ^ a b c Muda, R., 2009
- ^ International Society of Automation, http://www.isa.org/Template.cfm?Section=Communities&template=/TaggedPage/DetailDisplay.cfm&ContentID=23377 Archived 2013-12-12 at the Wayback Machine
- S2CID 119488975.
- ^ Figaro Sensor, http://www.figarosensor.com/products/general.pdf
- ^ a b Vitz, E., 1995
- ^ General Monitors, http://www.generalmonitors.com/downloads/literature/combustible/IR2100_DATA.PDF
- S2CID 229393321.
- ISSN 2168-9229.
- ^ a b Naranjo, E., http://www.gmigasandflame.com/article_october2007.html
- PMID 20836549.
- ^ Moore, James. "Calibration: Who Needs It?". Occupational Health and Safety Magazine. Archived from the original on December 2, 2011.
- ^ Colhoun, Jacquie. "Who is responsible for bump/challenge testing your gas detector". Archived from the original on 2014-02-27.
- ^ "Bump test saves lives". Archived from the original on 2014-03-12. Retrieved 2014-03-12.
- ^ Lang, M.A. (2001). DAN Nitrox Workshop Proceedings. Durham, NC: Divers Alert Network. p. 197. Archived from the original on October 24, 2008. Retrieved 2009-03-20.
{{cite book}}
: CS1 maint: unfit URL (link) - ^ Goble, Steve (2003). "Rebreathers". South Pacific Underwater Medicine Society Journal. 33 (2): 98–102. Archived from the original on 2009-08-08. Retrieved 2009-03-20.
{{cite journal}}
: CS1 maint: unfit URL (link) - ^ a b J. L. Martinez Hurtado and C. R. Lowe (2014), Ammonia-Sensitive Photonic Structures Fabricated in Nafion Membranes by Laser Ablation, ACS Applied Materials & Interfaces 6 (11), 8903-8908. http://pubs.acs.org/doi/abs/10.1021/am5016588
- ^ (OSHA) Source: Dangerous Properties of Industrial Materials (Sixth Edition) by N. Irving Sax
- ^ a b Matthew Peach, Optics.org. "Photonics-based MINIGAS project yields better gas detectors." Jan 29, 2013. Retrieved Feb 15, 2013.
- Breuer, W, Becker, W, Deprez, J, Drope, E, Schmauch, H . (1979) United States Patent 4141800: Electrochemical gas detector and method of using same. Retrieved February 27, 2010, from http://www.freepatentsonline.com/4141800.html
- Muda, R (2009). "Simulation and measurement of carbon dioxide exhaust emissions using an optical-fibre-based mid-infrared point sensor". Journal of Optics A: Pure and Applied Optics. 11 (1): 054013. .
- Figaro Sensor. (2003). General Information for TGS Sensors. Retrieved February 28, 2010, from http://www.figarosensor.com/products/general.pdf
- Vitz, E (1995). "Semiconductor Gas Sensors as GC detectors and 'Breathalyzers'". Journal of Chemical Education. 72 (10): 920. .
External links
- The Gas Detection Encyclopedia, Edaphic Scientific Knowledge Base