What are Hydrogen Compensated CO Sensors?

The combustion process creates a chemical reaction between hydrocarbons and oxygen to give heat as a by product. The process is a chemical melting pot as the hydrocarbon fuel splits into its constituent parts of hydrogen and carbon. In some circumstances unburnt hydrogen can be present in the flue in relatively low concentrations.

Most electrochemical sensors have a cross sensitivity to hydrogen. So if for example there were 1000 ppm of hydrogen present in the flue this might add 100 ppm to the CO reading. Effectively giving a false (high) reading.

The CO sensor used on the KM900 and KM9106 is specially designed to eliminate the effects of hydrogen cross sensitivity. The sensor contains an extra electrode that allows the effect of sensitivity to hydrogen to be counteracted within the electronics. So as well as the sensor being calibrated using a certified carbon monoxide test gas it is also calibrated using 1000 ppm of hydrogen. This ensures improved accuracy of the CO reading under all normal circumstances.