A flue gas analyser is an electronic instrument for measuring the levels of pollutants in the chimney or stack from a burning process. Generally, the flue gas analyser will be fitted with electrochemical sensors or possibly infrared sensors to measure the concentration of a number of pollutant gases. There are many general types in use, but there will be a pump for extraction of the sample from the stack and a bank of sensors in the flue gas analyser to measure the necessary components. Measurement of gas and ambient temperature are also needed to calculate the combustion parameters in the flue gas analyser. There are other options available, but these list the basic functions of a flue gas analyser used to quantify the efficiency and toxic nature of the gases produced by the burner. Flue gas analysers have changed over the years from simple chemical tests to advanced electronic instruments with a range of extra features and automatic calculation of all necessary combustion parameters.