Poison resistance, catalytic sensors

One of the common limitations of catalytic-combustion-type analyzers is the poisoning of the filament by silicon, sulfur, chlorinated compounds, or lead compounds. A variety of filament protection means have been added to increase the poison resistance of the sensors. Life expectancies are usually defined in terms of exposure concentration hours. One high-concentration exposure of a poison has been known to knock out a sensor therefore, nonpoisoning techniques should be considered when poisoning is an issue. 

The catalytic gas sensor has proven to be a most reliable and rugged means for the quantitative measurement of flammable gases in air, giving a measure of explosiveness irrespective of the composition of the gas mixture. The recent development of poison-resistant devices has overcome the problem of... 

The rapid growth in demand for catalytic flammable gas sensors to operate in hostile atmospheres (leaded petrol atmospheres, gas compressor stations, etc.) and areas where routine calibration and maintenance are difficult and costly (North Sea gas and oil platforms) has stimulated the search for sensing elements which are resistant to poisons. These devices generally take the form of a platinum wire coil embedded in a porous bead comprising active catalyst either dispersed throughout a porous substrate (5-7) or as discrete layers within the substrate (8). 

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