Evaluation of a chemical scrubber for the removal of airborne bacteria from recycled air.

The effectiveness of a chemical scrubber utilizing a recycled aqueous media was compared to high efficiency particulate air filtration in its ability to remove bacteria from recycled air. Two bacteria, Staphylococcus epidermidis and Bacillus subtilis, which have different biologic and physical properties were used in the study. The scrubber, using an aqueous chlorine-dioxide solution, and high efficiency particulate air filtration were equally effective in removing both types of bacteria from recycled air. Viable bacteria could not be recovered from the processed air following either treatment. When the scrubber was used with the chlorine dioxide solution, sufficient chlorine dioxide residues remained in the scrubber processed air to affect bacterial counts in the isolator to which the processed air was returned. The bacteria differed in their susceptibility to low levels of chlorine dioxide in the return air which influenced the number of viable organisms recovered under similar conditions. The use of water without a chemical additive eliminated bacteria in recycled air immediately following the start of the unit but allowed their eventual build-up in recycled air to concentrations of approximately half that of untreated air. Overall, the use of a chemical scrubber for the removal of bacteria from recycled air appeared to be no more effective than high efficiency particulate air filtration especially if the scrubbing media is recycled.