A method of metering a preselected volume of hydrogen peroxide into a vessel under vacuum is disclosed. The method comprises the steps of connecting a passage of known volume to the vessel under vacuum to evacuate the passage； sealing the passage； connecting the passage to a supply of hydrogen peroxide solution for a time sufficient to draw the hydrogen peroxide solution into the evacuated passage and fill the passage with the hydrogen peroxide solution； sealing the passage； and repeating steps a) to d) until a cumulative volume of fills of the passage is equal to the preselected volume. The volume of the passage is preferably 15 µL to 75 µL. Sterilization is controlled in an economic manner by obviating the need for a means to measure the hydrogen peroxide concentration in the chamber.
