Hydrogen peroxide sterilization method

A hydrogen peroxide metering unit for a hydrogen peroxide sterilizer having a hydrogen peroxide supply and a hydrogen peroxide vaporizer, the metering unit consisting of

• a body defining a metering passage having a fixed volume, an upstream end and a downstream end, the upstream end being connected only to the hydrogen peroxide supply, and the downstream end being connected only to the hydrogen peroxide vaporizer, for hydrogen peroxide flow from the hydrogen peroxide supply to the vaporizer through the metering passage;
• an inlet valve for closing the upstream end in a closed position and selectively connecting the upstream end of the metering passage to the hydrogen peroxide supply in an open position;
• an outlet valve for closing the downstream end in a closed position and selectively connecting the downstream end of the metering passage to the vaporizer in an open position;
• and
• a controller for operating the inlet and outlet valves reciprocally for opening only one of the valves at any given time,
• wherein the metering passage is evacuated when the outlet valve is in the open position, the inlet valve is in the closed position and the vaporizer is under vacuum;
• and subsequently the evacuated metering passage is filled with a volume of hydrogen peroxide equal to the fixed volume of the metering passage when the inlet valve is in the open position and the outlet valve remains in the closed position.