Decay of airborne contamination and ventilation effectiveness of cleanrooms

This article reports an investigation into the ability of the air supply in non-unidirectional cleanrooms to aid recovery from episodes of airborne contamination, and minimise airborne contamination at important locations. The ISO 14644-3 (2005) recovery test, which measures the rate of decay of test particles, was assessed and a reinterpretation of the test results suggested. This allowed air change effectiveness indexes to be calculated and used to evaluate the ventilation effectiveness of the cleanroom’s air supply. Air change effectiveness indexes were measured in various designs of cleanrooms, and reasons for deviations in the value of the indexes investigated.