In the event of a pandemic, the general public would use filters as protective devices. However, most commercial filters only remove airborne viruses physically without inactivating them, allowing reproduction on the surface and yielding the mask as a fomite. The objective of this study was to investigate the inactivation performance of dialdehyde starch (DAS) treated filters against airborne viruses. The viable removal efficiency by and relative survivability on the biocidal filters prepared with dialdehyde starch compared to untreated filters were investigated using MS2 bacteriophage at high relative humidity (80-90%) and room temperature. Experimental results showed no significant difference in viable removal efficiency and pressure drop between the treated and untreated filters for polypropylene filtering facepiece respirators. The pressure drop of DAS treated cellulose filters significantly decreased although there was no significant change in viable removal efficiency; the combination of these two factors resulted in an increase of filter quality. All biocidal filters showed a significantly lower relative survivability than untreated filters, and the relative survivability decreased as the concentration of DAS increased. The biocidal filter treated with 4% DAS presented an average of 30% survivability compared to the baseline of untreated filters. The results demonstrate that dialdehyde starch can be incorporated onto filters to provide an effective means for inactivating MS2 viruses through surface contact. (C) 2011 Elsevier Ltd. All rights reserved.