The sample gas coolers are specially designed for use in the emission monitoring. Thanks to the low dissolution rates of water-soluble gases very small concentrations of e.g. SO2 can be measured. In addition, the gas coolers are modular designed. This means a device can be equipped with humidity control, remote diagnosis, gas pump and acid dosing pump. There are some type of gas coolers such as Compressor, Peltier in continues and portable one.