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Two studies were conducted to assess the efficiency of air scrubbers to reduce airborne microorganisms in the exhaust air from animal houses. First, in a field study, the effects of a bio-scrubber and an acid scrubber on total bacterial counts were assessed. Higher bacterial counts were found in the outlet air compared to the inlet air of a bio-scrubber (increase from 6.1 × 10 4 to 2.4 × 10 5 CFU m-3), while an acid scrubber with sulfuric acid reduced bacterial emissions from 2.7 × 10 5 to 8.4 × 10 4 CFU m-3. Second, in a laboratory study, the effects of three disinfectants, added to the circulating water of an experimental air scrubber, on reductions of bacteria and virus were tested and compared with the effect of using only water. The air to the scrubber was extracted from four isolators each harboring seven roosters. Enterococcus faecalis and Gumboro vaccine virus were aerosolized in the air of one of the isolators. Hydrogen peroxide (H 2 O 2 ; 0.6%), peracetic acid (CH 3 CO 3 H; a solution of 0.13% acetic acid, 0.6% peroxide, and 0.13% peracetic acid), or ozone (O 3 ; 0.015%) were used as disinfectants. Peracetic acid was the only disinfectant that reduced bacteria and virus concentrations to below the sampler detection limits. We conclude that an acid scrubber with sulfuric acid is very useful at reducing ammonia emissions to the atmosphere but cannot significantly prevent emissions of microorganisms. Peracetic acid has a high potential to reduce these emissions and could replace or supplement sulfuric acid in existing scrubbers during periods of high risk of disease outbreak.

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