STATISTICALLY SIGNIFICANT EFFICIENCY TESTING OF HEPA FILTERS

摘要

A study was conducted to determine the minimum time needed to get statistically significantrnefficiencies of HEPA filters. A Poisson distribution was used to describe the variations and to calculaternthe lower and upper limits of measured counts at 95% confidence level. This study has shown 90rnseconds is sufficient for this test system to give a 99.990% efficiency or higher at 95% confidence.rnLonger tests will cause the mean measured efficiency to approach the filter’s true efficiency and alsornnarrow the confidence interval. However, challenging the HEPA filter with an oil aerosol for up to onernhour does not significantly change the filter’s true efficiency performance.