Which is more advanced, the electrochemical or photoionization type of toxic gas detectors?

Benzene is toxic; the photoionization principle is used for its detection, while toxic gases such as carbon monoxide and hydrogen sulfide are detected using electrochemical methods. Photoionization is a more advanced approach, but it is very expensive

Choose the appropriate one based on the different materials

5.2.3 The selection of commonly used combustible gas and toxic gas detectors shall comply with the following provisions: 1 For combustible light hydrocarbon gases, catalytic combustion or infrared gas detectors are recommended; when the air in the area of use contains substances such as sulfur, phosphorus, silicon, lead, and halogen compounds that can poison the catalytic combustion detection elements, anti-toxic catalytic combustion detectors, infrared gas detectors, or laser gas detectors should be used; in environments with low oxygen levels or high corrosivity, infrared gas detectors or laser gas detectors are preferable; for heavy hydrocarbon vapors, photoionization detectors can be used. 2 For hydrogen detection, catalytic combustion, electrochemical, or heat conduction detectors are suitable. 3 For organic toxic gases, semiconductor or photoionization detectors are appropriate. 4 For inorganic toxic gases, electrochemical detectors are recommended. 5 For oxygen detection, electrochemical detectors are suitable. 6 In areas with special climatic or production conditions and large open spaces that require monitoring, linear combustible gas detectors are advisable. 7 In areas where the gases or vapors resulting from process medium leaks can significantly change the temperature of the environment around the source of release, infrared imaging detectors can be used. 8 In areas where the noise generated by high-pressure process medium leaks can significantly affect the sound pressure level in the area around the source of release, noise detectors can be employed. 9 In areas where temporary detection of combustible gases and toxic gases is necessary during production or maintenance, portable gas detectors should be installed.

It is truly my lack of expertise and familiarity with this industry that has limited my imagination; I thought that electrochemical analysis instruments were mainly used for water quality testing, but it seems that their applications are much broader than I had imagined. Although I am not familiar with toxic gas detectors, in the field of analytical testing that I know about, electrochemical instruments are generally convenient, fast, and cost-effective options.