Mass flow meters based on gas measurement give the user the ability to measure the rate of mass flow of the gas in industrial pipes and processes directly. This method makes use of thermal mass flow, whereby the heat transfer from the heated element to the gas stream gives information about the gas flow rate. It is widely used for process monitoring, gas usage measurement, flow control, and distribution. Some of the important selection criteria include the type of gas to be measured, range of flow, pipe size, pressure, temperature, accuracy, installation, and outputs.