Development of a functional and disinfectable sewage vent high-efficiency particulate air filter system and its validation using vaporized hydrogen peroxide.

Airborne disinfection of high-containment facilities is mandatory for safe operations. However, sewage vent air-particularly in large-animal experimental units-can represent a critical gap and is typically not considered in the design of high-efficiency particulate air (HEPA) filter systems. Here, we present an engineering design enabling HEPA filtration of sewage vent air from primary biological containments, including large-animal facilities and necropsy suites. We additionally evaluated vaporized hydrogen peroxide (vH2O2) fumigation as an airborne disinfection approach. Disinfection efficacy was determined by quantitative carrier testing using commercial spore carriers (CSC) coated with 106 spores of Geobacillus stearothermophilus and compared with germ carriers coated with surrogate viruses, mycobacteria, and other spores. Temperature, relative humidity (RH), and vH2O2 concentration were monitored in real time to define process parameters and validate protocols targeting ≥4 log10 reduction. Inactivation efficacy differed substantially among challenge agents: CSC were least resistant to inactivation, whereas murine norovirus (MNV) on germ carriers was most challenging to inactivate. At medium-high vH2O2 concentrations (up to 520 parts per million [ppm]), increasing RH was the dominant driver of inactivation. Based on these data, we developed a biphasic disinfection cycle maintaining a saturated humidity environment with ~35% H2O2 for ≥10 h, achieving ≥4 log10 reduction of MNV infectivity and G. stearothermophilus spore viability on germ carriers. Overall, vH2O2 under high-to-saturated RH is an effective means to disinfect technical infrastructure in biological containment settings handling high-consequence pathogens.IMPORTANCEVent air from sewage systems in biological containment facilities where large animals are kept should be considered a contaminated waste stream. Therefore, effective high-efficiency particulate air (HEPA) filter systems that prevent mold or other moisture-related deterioration of the filters need to be installed. Airborne vaporized hydrogen peroxide (vH2O2) is an appropriate method to decontaminate these complex HEPA filter systems. High to saturated humidity is required for virucidal and sporicidal efficacy under medium to high concentration of vH2O2. Commercially available spore carriers are artificial in design, resulting in lower resistance to inactivation compared to custom germ carriers coated with non-enveloped viruses and thus should be avoided as read-out (validation means) by the biosafety community working with high-consequence pathogens in primary containments.