2. Detection principles

Measuring the concentration of a gas (or vapour) is based on its physical or chemical properties, usually the property that is particularly sensitive to the presence and variation of the concentration of this gas, or specific to this gas.

• The main properties used in commercial devices are :

  • physical properties :

    • thermal conductivity,

    • absorption of light radiation,

    • adsorption on a material,

    • sound level of an ultrasonic leak ;

  • chemical...