Particle dispersion in a cleanroom - Effects of pressurization, door opening and traffic flow

Air cleanliness is of particular importance in clean environments, as a small source of contamination can highly disturb the true function of space. One common-place approach is to establish a positive pressure relative to adjacent areas that would avoid unwanted airborne particles. However, door operation and the movement of traffic may result in air mixing across the cleanroom door. This paper presents the results of a series of experiments to characterize the effect of pressure difference, traffic flow and door opening on cross-contamination and air quality inside the cleanroom. The experiments were conducted in an actual cleanroom where an oil-based substance was aerosolized in neighbouring areas, and its path inside the cleanroom was studied. Results suggested that the higher-pressure differentials were more effective to prevent aerosols to enter the cleanroom. Door operation can eliminate, and even reverse the pressurization across the door. Under a higher-pressure difference, however, it took a much shorter time for positive pressure to recover. The results of this work will be useful in determining the optimal settings of cleanroom operation, where the probabilities of contamination from an outside source are minimized.