Toxic Gas Detectors Working Principle

Toxic Gas Detectors

Major 2 categories are available:

  1. Detectors for gases which create an immediate health hazard (eg. H2S, CO, HF, HCl, Cl2)

  2. Detectors for gases that create a health hazard on long term exposure (eg. Vinyl Chloride, Benzene, Toluene etc.)

H2S detectors:

The two types of H2S detectors available are:

a. Electro-chemical cell type:

This type is based on an electro-chemical cell, developed to react exclusively to H2S. As a result of chemical reaction of the cell organic electrolyte with H2S, an electric current is generated, which is proportional to the H2S concentration in the sample gas.

b. Semi-conductor (MOS) type:

Working principle: The semi-conductor type is based on the adsorption of H2S molecules on the surface of a solid-state semi-conductor crystal which causes a change in electrical resistance of the electrical circuit of which the semi-conductor forms the part.

Set Point: H2S detectors have a typical recommended minimum alarm setting of 5 ppm. If second stage alarm is used, 10 ppm shall be used.


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