Abstract
International standards as well as national regulations often require the incorporation of HEPA filters in the exhaust of BSL-3 (unless work with non-airborne organisms is performed—Swiss Containment Ordinance [Federal Council, 2012]) and certainly BSL-4 laboratories (single HEPA filter on supply and double HEPA filter on exhaust). These may need to be decontaminated from time to time, for example prior to filter integrity testing (protection of the testing equipment in case filters or seals are damaged and thus leaking) or when exchanging filters (bag-in/bag-out may offer an alternative or an additional safety measure, respectively). However, HEPA filter housings are not generally equipped with sample ports that allow for placement of indicators to confirm a successful fumigation process. Additionally, a site-specific risk assessment concluded that since the filter boxes are situated in an area deemed to remain non-contaminated at all times (HEPA filter floor above laboratory suites), indicators may not be placed inside the filter housings as opening them prior to fumigation would open containment and thus pose a threat to the people working on the filter boxes as well as to the environment.
In this article the authors describe the use of the IndicatorSafe, a simple and cheap solution to the above-mentioned problem. Placing the IndicatorSafe in the return line following the filter housing was shown to be an efficient alternative when fumigating filter housings with vaporized hydrogen peroxide (VHP), as shown during the validation of filter housing fumigation cycles, and may likely be adapted to other fumigation methods on the market.