Gas detectors are highly sophisticated instruments that measure or monitor one or more gases within an area. Designed to detect combustible gases, toxic gases, and oxygen depletion; gas detectors are usually part of a safety system and are typically deployed in confined spaces or in other areas where gas hazards could lead to toxic exposure or fire risk.

Gas detectors are either portable or fixed in design. Portable gas detectors are used as personal safety devices and are worn on clothing or on a belt/harness when entering confined spaces or other hazardous environments.. These devices typically sound an alarm when the target gas is detected allowing the wearer an opportunity to safely leave the area.

Fixed gas detectors are generally mounted near the process area of a plant or control room and interface with a SCADA system for continuous monitoring and automatic shutdown if a target gas is detected.

Gas Detector Technologies

Gas detectors are categorized by the type of gas they detect and the technology used.

Toxic Gas Detectors:

  • Electrochemical sensors are generally used to detect toxic gases such as carbon monoxide, chlorine and nitrogen oxides. Electrochemical sensors are highly sensitive and emit an electrical signal when the electrode comes in contact with the target gas.
  • Metal Oxide Semiconductors also detect toxic gases and utilize a gas sensitive film that is composed of tin or tungsten oxides. The film reacts with gases, triggering the device when toxic levels are present. Metal oxide sensors operate well in low-humidity ranges and are able to detect a range of gases, including combustibles.

Combustible Gas Detectors:

  • Catalytic sensors operate on the principle that when a combustible gas/air mixture passes over the hot surface of a catalyst, combustion occurs and the resulting heat increases the temperature of the sensing element. This in turn alters the resistance of a platinum coil and can be measured by using the coil as a temperature thermometer in a standard electrical bridge circuit. The resistance change is then directly related to the gas concentration in the surrounding atmosphere.
  • Infrared sensors work via a system of transmitters and receivers to detect combustible gases, specifically hydrocarbon vapors. Typically, the transmitters are light sources and receivers are light detectors. If a gas is present in the optical path, it will interfere with the power of the light transmission between the transmitter and receiver. The altered state of light determines if and what type of gas is present.

Gas Detector Maintenance and Calibration:

Although gas detectors are generally a reliable technology, their proper function is dependent on proper maintenance and calibration. Many sensors have a shelf life so it's imperative to be aware of the needs of your individual system. Calibration and bump-testing is an important element of regular maintenance as it confirms the instrument measures gas levels correctly and sounds alarms when intended.

If you have any questions regarding gas detectors please don't hesitate to speak with one of our engineers by e-mailing us at sales@instrumart.com or calling 1-800-884-4967.