The electro-chemical gas analyser is designed to measure the concentration of flue gas constituents (O2, CO, NO, NO2, SO2, H2S). For each flue gas constituent, there are 2-3 electrodes which are specifically made to measure only that particular flue constituent by uising an electrolytic matrix which which only reacts with that flue constituent in interest. The redox reaction occuring on the surface of the electrodes causes the potential to fall and rise. The fall and rise of the potential is correlated to the concentration of the flue gas constituent. However, the measurements are subjected to disturbances by fluctuation in pressure and temperature.