Confirm the type of gas to be detected and the concentration range.
Each production department encounters different types of gases. When selecting a gas detector, all possible situations need to be taken into account. If methane and other alkanes with relatively low toxicity are predominant, choosing an LEL detector is undoubtedly the most appropriate. This is not only because the principle of the LEL detector is simple and it has a wide range of applications, but also because it has the characteristics of being easy to maintain and calibrate. If there are toxic gases such as carbon monoxide and hydrogen sulfide, a specific gas detector should be prioritized to ensure the safety of workers. If there are more organic toxic and harmful gases, considering that their concentrations that may cause poisoning to personnel are relatively low, such as aromatic hydrocarbons, halogenated hydrocarbons, ammonia (amines), ethers, alcohols, esters, etc., the photoionization detector introduced in the previous chapter should be selected, and it is definitely not advisable to use an LEL detector to deal with them, because this may lead to casualties.
If the types of gases cover the above several categories, choosing a compound gas detector may achieve twice the result with half the effort.
Determine the usage scenario:
Due to the differences in industrial environments, the types of gas detectors selected are also different.
A) Fixed gas detector:
This is a detector that is widely used in industrial installations and production processes. It can be installed at specific detection points to detect the leakage of specific gases. Fixed detectors are generally two-piece. The detection head composed of a sensor and a transmitter is installed at the detection site as one unit, and the secondary instrument composed of a circuit, power supply, and display and alarm device is installed in a safe place as one unit for easy monitoring. Its detection principle is the same as that described in the previous section, but in terms of technology and process, it is more suitable for the characteristics required for fixed detection, such as continuity and long-term stability. They also need to be selected according to the types and concentrations of gases at the site. At the same time, attention should be paid to installing them at the parts where specific gases are most likely to leak. For example, the most effective installation height of the sensor should be selected according to the specific gravity of the gas, and so on.
