What is a Combustible Gas Detector?

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  • Written By: M. McGee
  • Edited By: Jenn Walker
  • Last Modified Date: 03 October 2019
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A combustible gas detector is a device that senses the presence of harmful gases and alerts people to the hazard. There are two main methods of detecting combustible gases: controlled combustion and infrared technology. Each of these methods has its own advantages and disadvantages, although the infrared methods are typically safer overall. In addition to combustible gas detectors, there are a wide array of other devices that detect non-combustible harmful gases.

In most cases, a combustible gas detector is a handheld or similarly sized device. They generally run on batteries and are easy to transport and set up. This allows users to take them into places where there may be harmful gases and get a reading immediately. In nearly all cases, these devices have audible alarms that are very loud. These alarms alert nearby people to the danger, giving them time to evacuate or stop the problem before it gets out of hand.

Some types of combustible gas detectors actually heat the gases to the point of combustion to detect them. This is done within a controlled environment inside the detector. These are the original types of detectors and have been around for many years.


A controlled combustion combustible gas detector uses a special type of circuit called a Wheatstone bridge. This circuit measures the current flow between two points inside the detector. When combustible gas enters the chamber with the circuit, one half of the circuit is warm enough to ignite the gas, or it contains a combustion catalyst. When the gases combust, the heat present in the testing area changes and the flow of electricity over the circuit is altered. This change triggers the alarm in the device.

An infrared combustible gas detector works in a totally different way. As gas moves into the testing chamber, a beam is shot at it. The beam splits before it actually reaches the gas; one half goes into the gas to a receiver, and the other goes back to the emitter. The detector measures the intensity of the two beams to determine if combustible gas is present. When the beams are the same, everything is fine, but changes in the intensity of the gas-side beam could mean there is a problem.

Along with combustible gas detectors, there are a wide range of other gas detectors on the market. Since there are so many gases that are harmful to humans, these detectors are an important safety feature both commercially and residentially. Simple detectors such as carbon monoxide and radon should be present in every home and workplace.


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