A method of controlling unwanted condensation of hydrogen peroxide in a sterilization chamber at a preselected temperature is disclosed. The method includes the steps of maintaining the sterilization chamber at a vacuum pressure below the pressure at which hydrogen peroxide will boil at the preselected temperature, evaporating successive pulses of hydrogen peroxide, and injecting the evaporated hydrogen peroxide into the chamber, whereby the volume of each pulse of hydrogen peroxide is less than 75 μL, preferably less than 35 μL, most preferably less than 20 μL. Sterilization results are improved by controlling unwanted condensation of hydrogen peroxide.
