Poisoning of the Sensor
The Catalytic elements are liable to be rendered inactive due to ‘poisoning’ by certain groups or compounds.
In general, contact with any gaseous compound capable of producing an involatile residue upon heating is to be avoided.
Examples of such substances are:
a. Silicon containing vapours, as emitted by silicone polishes, greases and oils.
b. Petroleum vapour containing tetra-ethyl lead or other organo-metalllic compounds.
c. Phosphorus in the form of phosphate esters.
These compounds will permanently affect the detector and if their presence is suspected, the response of the detector should be determined by the calibration procedure.
It is also possible that the reaction of the detector to a flammable gas could be inhibited by halogen containing gases such as chloroform, carbon tetra chloride and trichloroethylene. This effect is not permanent.