Gas detector
Encyclopedia
A gas detector is a device which detects the presence of various gases
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.
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 continous monitoring and where a tripping interlock can be activated for an emergency situation.
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
, or as part of feeback loop which maintains a constant partial pressure
of oxygen in a rebreather
.
Gas
Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...
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
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
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.
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 continous monitoring and where a tripping interlock can be activated for an emergency situation.
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. Almost every portable gas detector out there has a specific calibration gas requirement which is available from the manufacturer you purchased your monitor from.Oxygen concentration
Oxygen deficiency gas monitors are used for employee and workforce safety. Cryogenics such as liquid nitrogen (LN2), helium (He), and 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, MRI rooms, pharmaceutical, semiconductor, and cryogenic suppliers are typical customers.Oxygen fraction in a breathing gas is measured by electro-galvanic fuel cell
Electro-galvanic fuel cell
An electro-galvanic fuel cell is an electrical device, one form of which is commonly used to measure the concentration of oxygen gas in scuba diving and medical equipment....
sensors. They may be used stand-alone, for example to determine the proportion of oxygen in a nitrox mixture used in scuba diving
Scuba diving
Scuba diving is a form of underwater diving in which a diver uses a scuba set to breathe underwater....
, or as part of feeback loop which maintains a constant partial pressure
Partial pressure
In a mixture of ideal gases, each gas has a partial pressure which is the pressure which the gas would have if it alone occupied the volume. The total pressure of a gas mixture is the sum of the partial pressures of each individual gas in the mixture....
of oxygen in a rebreather
Rebreather
A rebreather is a type of breathing set that provides a breathing gas containing oxygen and recycled exhaled gas. This recycling reduces the volume of breathing gas used, making a rebreather lighter and more compact than an open-circuit breathing set for the same duration in environments where...
.
Hydrocarbons and VOCs
Detection of hydrocarbons can be based on the mixing properties of gaseous hydrocarbons – or other volatile organic compounds – and the sensing material incorporated in the sensor. The selectivity and sensitivity depends on the molecular structure and concentration; however it is difficult to design a sensor capable of detecting only one single type of molecule.Combustible
- Catalytic bead sensorCatalytic bead sensorA catalytic bead sensor is a type of sensor that is used for gas detection.-Principle:The catalytic bead sensor consist of two coils of fine platinum wire each embedded in a bead of alumina, connected electrically in a Wheatstone bridge circuit. One of the pellistors is impregnated with a special...
- ExplosimeterExplosimeterAn explosimeter is a device which is used to measure the amount of combustible gases present in a sample. When a percentage of the lower explosive limit of an atmosphere is exceeded, an alarm signal on the instrument is activated...
- Infrared point sensorInfrared point sensorA infrared point sensor is a point gas detector based on the nondispersive infrared sensor technology.-Principle:Dual source and dual receivers are used for self compensation of changes in alignment, light source intensity and component efficiency. The transmitted beams from two infrared sources...
- Infrared open path detectorInfrared open path detectorInfrared open-path gas detectors send out a beam of infrared light, detecting gas anywhere along the path of the beam. This linear 'sensor' is typically a few metres up to a few hundred metres in length...
Other
- Flame ionization detectorFlame ionization detectorA flame ionization detector is a type of gas detector used in gas chromatography. The first flame ionization detector was developed in 1957 by scientists working for the CSIRO in Melbourne, Australia....
- Nondispersive infrared sensor
- Photoionization detectorPhotoionization detectorA photoionization detector or PID is a type of gas detector.Typical photoionization detectors measure volatile organic compounds and other gases in concentrations from sub parts per billion to 10 000 parts per million . The photoionizaton detector is an efficient and inexpensive detector for many...
- Zirconium oxide sensor cell
- Catalytic sensors
- Metal oxide semiconductor
- Gold film
- Detector tubes
- Sample collection and chemical analysis
- Piezoelectric microcantilever
- Holographic SensorHolographic sensorA holographic sensor is a device that comprises a hologram embedded in a smart material that detects certain molecules or metabolites. This detection is usually a chemical interaction that is transduced as a change in one of the properties of the holographic reflection , either refractive index or...
- Thermal Conductivity DetectorThermal conductivity detectorThe thermal conductivity detector , also known as a Katharometer, is a bulk property detector and a chemical specific detector commonly used in gas-liquid chromatography. This detector senses changes in the thermal conductivity of the column effluent and compares it to a reference flow of carrier gas...
Manufacturers
- Gas Measurement Instruments Ltd
- Mine Safety Appliances
- Detcon Inc.
- Sensidyne Fixed Point and Open Path Gas Detection Systems
- 3M3M3M Company , formerly known as the Minnesota Mining and Manufacturing Company, is an American multinational conglomerate corporation based in Maplewood, Minnesota, United States....
- Honeywell AnalyticsHoneywell AnalyticsHoneywell Analytics is a producer of gas detector based in Poole in the United Kingdom.-Origins of the Organisation:Originally incorporated as EIC-Sieger in 1959 and later re-branded as J&S Sieger Ltd in 1961, the company revolutionised the fledgling gas detection industry, when its founder, Joshua...
- MSR Electronic
- Sperian
- DrägerDrägerThe Drägerwerk AG is a German company based in Lübeck which makes breathing and protection equipment, gas detection and analysis systems, and noninvasive patient monitoring technologies. Customers include hospitals, fire departments and diving companies....
- Industrial Scientific CorporationIndustrial Scientific CorporationIndustrial Scientific Corporation, or ISC, develops, manufactures, and services fixed and portable gas detection equipment. Key markets include utilities, chemical production, oil and gas, steel and coke, paper industry, fire service, construction, military, insurance companies, food and drinks,...
- Uniphos
- Linde G-TECTA
- respoRAE