Development of a Method for Measuring Single-Pass Bioaerosol Removal Efficiencies of a Room Air Cleaner

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Abstract
This paper presents the development of a method to measure singlepass microbial particle reduction by a room air cleaner having a built-in blower. The method used a Collison nebulizer to generate bioaerosol challenge for injection into a 14 m3/min airflow duct. Bioaerosol samplers (impactors) were used to obtain upstream and downstream samples. The success of the method required ensuring the survivability and culturability of the organisms, the selection of appropriate test organisms for this application, the implementation of the necessary control tests, the development of good sampling protocols, and the use of nonbiological aerosol tests for comparisons and Quality Assurance/Quality Control (QA/QC) checks. A series of filtration efficiency tests was performed on only the filter elements of the air cleaner. The tests were conducted with two Gram-positive bacteria, Bacillus subtilis and Staphylococcus epidermidis , and, for comparison and QA/QC purposes, two nonbiological challenge aerosols. The biological data compared well with the nonbiological particulate test results, and both results were highly reproducible. Next, a series of filtration efficiency tests was performed on the entire air cleaner assembly using five different biological aerosols (two bacteria, two fungi, and a virus). For these tests the air cleaner was mounted in a test duct with the built-in fan operating and the flows balanced to simulate free-standing operation. The results of these tests were also highly repeatable and correlated well with the nonbiological test results.
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