It is very important to keep different pressure among rooms with different cleanness in
pharmaceutical factories, semiconductor factories and so on. However, a trouble, that caused by the
room pressure changes, is frequently detected at commissioning systems and results in significant
losses of time and money. A method of design review, by use of a simulation, is proposed in this paper
to prevent trouble of room pressure change. The commissioning test removes the causes of the trouble
in the design stage. This paper notes simulation results of the air-conditioning systems. The simulator
is made by MATLAB and SIMULINK. The developed method of this simulator is expounded by use
of Base-model in which all kind of elements of air-conditioning components are included. When
room pressure of the Base-model is controlled, the simulator measures room pressure change and
flow rate change. The simulator can evaluate the systems beforehand only by design information. As
an example of evaluation of the systems, an actual air-conditioning system, where the room pressure
change trouble occurs, is verified. It adequately explains the cause and solution of this trouble.