According to the World Health Organization, 99% of the global population is breathing low quality air, resulting in 3.2 million premature annual deaths of which 21% are attributed to air quality-related respiratory infections. The recent coronavirus (CoVid-19) pandemic, responsible for more than 6.8 million deaths worldwide, has highlighted the often neglected issue of air quality in human health. Air filtration is an established method to ensure a good indoor air quality, being effective at capturing airborne pathogens and preventing diseases such as asthma. Current air filter media, is either made of fiberglass or synthetic materials such as polypropylene due to its low cost. With usage, water from air humidity, dust and dirt, including fungi and bacteria spores, can accumulate on filters creating ideal conditions for the propagation of microorganisms. Thus, the filter can become a secondary source for airborne pathogens.

In this work, antiviral and antimicrobial filters were prepared by spray coating of Ag₂O, CuO and ZnO particles into commercially available air filters. The reliability of the filters was tested through particle release in air (through a scanning mobility particle sizer (SPMS)). Filtration performance was measured against an aerosol of iron nanoparticles in nitrogen gas produced through a Spark Discharge Generator (SGS). The biosafety of the filters was measured in vitro through cytotoxicity tests against L-929 mouse fibroblasts cells. Antibacterial efficiency was measured in vitro against two clinically relevant pathogens: S. pneumoneae and P. aeruginosa. Anti-viral performance was measured against respiratory syncytial virus (RSV). In general, the results have shown that spray coating is a reliable solution, with no detectable cytotoxicity effects or particle release in air. After functionalization, both Ag₂O and CuO compounds have been shown to be effective against RSV, with total antiviral activity (over 99%), while only Ag2O presented a clear antibacterial action. Thus, the spray coating as post-manufacturing functionalization of air filters can be an efficient, low cost solution against airborne pathogens.