A partial removal of metallic mercury from air by fiber-based trickle-bed bioreactors was observed. Up to 50 to 65% of the inlet mercury concentrations of 35 to 70 μg/m 3 were removed by immobilized live Pseudomonas bacteria for up to 275 hours at a residence time of 1 min. Ninety to 125% of the adsorbed mercury was recovered by a direct assay after dismantling the bioreactors, thus confirming that the observed mercury removal was due to its adsorption by biomass rather than wet scrubbing followed by evaporation. However, mercury removal at a lower inlet concentration (23 μg/m 3) was negligible, with a poor material balance. The adsorbed mercury at higher inlet concentrations was not removed from the biomass by a 2-week washing after conclusion of the mercury adsorption experiment, which indicates a strong mercury binding by bacteria. The volatile organic compound removal efficiency was not affected by the presence of up to 70 μg/m 3 of metallic mercury in the air.