Abstract
Integrity tests on 969 HEPA filters filtering air to and from rooms and laboratories have been done annually for 13 years. Filter replacements were analyzed by supply or exhaust air system, area serviced, primary or secondary situations and cause for replacement. The average annual filter replacement rate for installations filtering either supply or exhaust air, or vented gases were 2.9%, 1.9%, or 3.0% respectively. Initially, most failures occurred in the filter medium or the gasket seal. However, in recent years, there has been a general increase in filter reliability with filter blockage being the major reason for replacement. The replacement rates for exhaust filters in laboratory, animal room or other plant rooms were similar.
This study has shown that the critical biocontainment function of HEPA filters in this biological laboratory has been exceptionally reliable with little deterioration in performance over 13 years of service. Because a majority of filters (up to 78% for exhaust systems) have never been replaced, it was not possible to determine a meaningful life expectancy for filters.