In order to improve the performance of the old Stack Simulator, NIM built two new facilities. One is a close loop wind tunnel, which can simulate the real flue gas conditions. The wind tunnel can change the flow rate, temperature, pressure, gas composition and turbulence in the test section. It is used to calibrate the velocity measurement devices such as three-dimensional pitot tubes used in Relative Accuracy Test Audit (RATA). Another facility is a new Stack Simulator, which can simulate the flow field conditions in the real stack. It is used to evaluate the average velocity measurement of RATA devices.