Sterilization by H2O2 droplets under corona discharge

A new sterilization method that combines an injection of hydrogen peroxide droplets (30 wt%) by spraying and a corona discharge is very effective for high-speed sterilization. Ultraviolet light, gaseous species and fine H2O2 droplets were considered to be important factors of this sterilization method. In order to investigate the sterilization mechanism, these three factors were examined. It was shown that ultraviolet light was not effective for sterilization. Among the gaseous species investigated, positive ions were proved to be effective through experiments using electric fields. A quadrupole mass spectrometer was used to measure positive ions. It was confirmed that H2O2 was decomposed and the number of H2O2 droplets was reduced. H2O2 droplet size was measured by a laser scattering method, CNC (condensation nuclei counter) and DMA (differential mobility analyzer). It was found that droplets larger than 3 nm still existed even if the droplet size was reduced. It was concluded that both fine H2O2 droplets and positive ions had important effects on sterilization.