Equations have been recently derived by Whyte, Lenegan and Eaton for calculating the airborneudconcentration of particles and microbe-carrying particles in non-unidirectional airflow cleanrooms.udThese equations cover a variety of ventilation systems, and contain the variables of air supply rate,udairborne dispersion rate of contamination from machinery and people, surface deposition of particlesudfrom the air, concentration of contamination in fresh make-up air, proportion of fresh air, and airudfilter efficiencies. The relative importance of these variables is investigated in this present researchudpaper, with particular regard to the removal efficiency, location, and number of air filters. It wasudshown that air filters were important in ensuring low levels of contamination in cleanrooms but theudtypes of filters specified in current cleanroom designs were very effective in ensuring a minimaludcontribution to the cleanroom’s airborne contamination especially when a secondary filter is used inudaddition to a primary and terminal filter. The most important determinants of airborneudcontamination were the air supply rate and the dispersion rate of contamination within theudcleanroom, with a lesser effect from deposition of airborne particles onto cleanroom surfaces. Theudinformation gathered confirmed the usefulness of the equation previously used by Whyte, Whyte,udEaton and Lenegan to calculate the air supply rate required for a specified concentration of airborneudcontamination.
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