Equations are derived in this paper for predicting the airborne concentration of particles andudmicrobe-carrying particles in non-unidirectional airflow cleanrooms during manufacturing. Theudequations are obtained for a variety of ventilation systems with different configurations for mixingudfresh and recirculated air, air filter placements, and number and efficiency of air filters. Theudvariables in the equations are air supply rate, airborne dispersion rate of contamination fromudmachinery and people, surface deposition of particles from air, particle concentration in fresh makeupudair, proportion of make-up air, and air filter efficiencies. The equations are amenable to relativelyudsimple modification for the study of different cleanroom ventilation systems. The use of theseudequations to investigate the effect of different configurations of ventilation systems and the relativeudimportance of the equation variables on airborne concentrations will be reported in a further paper.
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