Incomplete combustion reduces the efficiency of a burner system by wasting fuel. The main causes of incomplete combustion are carbon monoxide in the flue gas and, to a lesser extent, hydrocarbons such as methane. Hydrogen is generally also present at least in traces, but the calculation for incomplete combustion just considers carbon monoxide in most cases, and methane if the appropriate sensor is fitted. With today's burners producing very little carbon monoxide, the relevance of loss by incomplete combustion will probably disappear in time, but it is still a parameter to be considered now. As can be seen from the formula, the loss by incomplete combustion is dependent on the correct fuel being set in the analyser. These factors make a contribution to the total losses of the system that should not be ignored, even if they are relatively small and perhaps appear insignificant.