Evaluation of Vaporized Hydrogen Peroxide Fumigation as a Method for the Bio-decontamination of the High Efficiency Particulate Air Filter Unit

Objective To evaluate the performance of vaporized hydrogen peroxide （VHP） for the bio-decontamination of the high efficiency particulate air （HEPA） filter unit. Methods Self-made or commercially available bioindicators were placed at designated locations in the HEPA filter unit under VHP fumigation. The spores on coupons were then extracted by 0.5 h submergence in eluent followed by 200- time violent knocks. Results Due to the presence of HEPA filter in the box, spore recovery from coupons placed at the bottom of the filter downstream was significantly higher than that from coupons placed at the other locations. The gap of decontamination efficiency between the top and the bottom of the filter downstream became narrower with the exposure time extended. The decontamination efficiency of the bottom of the filter downstream only improved gently with the injection rate of H202 increased and the decontamination efficiency decreased instead when the injection rate exceeded 2.5 g/min. The commercially available bioindicators were competent to indicate the disinfection efficiency of VHP for the HEPA filter unit. Conclusion The HEPA filter unit is more difficult than common enclosure to decontaminate using VHP fumigation. Complete decontamination can be achieved by extending fumigation time. VHP fumigation can be applied for in-situ biodecontamination of the HEPA filter unit as an alternative method to formaldehyde fumigation.

Identification of Model Parameters of Vaporized Hydrogen Peroxide Decomposi-tion Flux on Building Materials for Compu-tational Fluid Dynamics

To maintain healthy and sanitary indoor air quality, development of effective decontamination measures for the indoor environment is important and hydrogen peroxide is often used as decontamination agent in healthcare environment. In this study, we focused on the decomposition phenomena of vaporized hydrogen peroxide on wall surfaces in indoor environment and discussed a wall surface decomposition model for vaporized hydrogen peroxide using computational fluid dynamics to simulate the concentration distributions of vaporized hydrogen peroxide. A major drawback to using numerical simulations is the lack of sufficient data on boundary conditions for various types of building materials and hence. We also conducted the fundamental chamber experiment to identify the model parameters of wall surface decomposition model for targeting five types of building materials.

Disinfection efficiency of positive pressure respiratory protective hood using fumigation sterilization cabinet

Concerns have been raised about both the disinfection and the reusability of respiratory protective equipment following a disinfection process.Currently,there is little data available on the effects of disinfection and decontamination on positive pressure respiratory protective hoods(PPRPH).In this study,we evaluated the effect of vaporized hydrogen peroxide(VHP)on the disinfection of PPRPH to determine applicability of this method for disinfection of protective equipment,especially protective equipment with an electric supply system.A hydrogen peroxide-based fumigation sterilization cabinet was developed particularly for disinfection of protective equipment,and the disinfection experiments were conducted using four PPRPHs hung in the fumigation chamber.The pathogenic microorganism Geobacillus stearothermophilus ATCC 7953 was used as a biological indicator in this study and the relationship between air flow(the amount of VHP)and disinfection was investigated.Both function and the material physical properties of the PPRPH were assessed following the disinfection procedure.No surviving Geobacillus stearothermophilus ATCC 7953,both inside and outside of these disinfected PPRPHs,could be observed after a 60 min treatment with an air flow of 10.5–12.3 m^(3)/h.Both function and material physical properties of these PPRPHs met the working requirements after disinfection.This study indicates that air flow in the fumigation chamber directly influences the concentration of VHP.The protective equipment fumigation sterilization cabinet developed in this paper achieves the complete sterilization of the PPRPHs when the air flow is at 10.5–12.3 m^(3)/h,and provides a potential solution for the disinfection of various kind of protective equipment.