This study assessed the antimicrobial activity of nanoparticles (consisting of a mixture of silver nitrate and titanium dioxide) and nanoparticle-coated facemasks to protect against infectious agents. The minimum inhibitory concentrations of the nanoparticles against Escherichia coli and Staphylococcus aureus were 1/128 and 1/512, respectively. The antibacterial activity of nanoparticle-coated masks was quantified according to the procedures of AATCC 100-1999. A 100% reduction in viable E. coli and S. aureus was observed in the coated mask materials after 48 h of incubation. Skin irritation was not observed in any of the volunteers who wore the facemasks. Nanoparticles show promise when applied as a coating to the surface of protective clothing in reducing the risk of transmission of infectious agents.