Sterilization Method and Apparatus

Abstract

Disclosed is a method of sterilizing an article by sequentially exposing the article under vacuum first to a gaseous conditioning agent for forming radicals and then to a sterilant. The preferred conditioning agent is hydrogen peroxide and the preferred sterilant is ozone. The chamber is initially evacuated to a first vacuum pressure and then sealed for the remainder of the sterilization process and during all sterilant injection cycles, without removal of any component of the sterilization atmosphere, which means without any measures to reduce the water vapor content. Keeping the chamber sealed and maintaining the conditioning agent and the radicals generated thereby in the chamber for the sterilization with sterilant results in a synergistic increase in the sterilization efficiency and allows for the use of much lower sterilant amounts and sterilization cycle times than would be expected from using the conditioning agent and the sterilant in combination.

1 .- 8 . (canceled) 
     
     
         9 . A method for sterilizing an article in a sealable sterilization chamber, comprising the steps of
 a. placing the article into the sterilization chamber,   b. sealing the sterilization chamber,   c. applying to the sterilization chamber a vacuum of a first pressure,   d. injecting into the sealed sterilization chamber gaseous hydrogen peroxide as conditioning agent for forming free radicals and until a second pressure is reached,   e. maintaining the sterilization chamber sealed for a first exposure period,   f. injecting into the sealed sterilization chamber, after the first exposure period, nitrogen oxide as sterilant gas for creating or regenerating the free radicals in the sealed sterilization chamber,   g. continuing to maintain the sterilization chamber sealed for a second exposure period,   h. evacuating the sterilization chamber at the end of the second exposure period for removing all residual sterilant gas from the sterilization chamber,   i. returning the sterilization chamber to atmospheric pressure, and   j. removing the sterilized article from the sterilization chamber.   
     
     
         10 . The method of  claim 9 , wherein step d) includes injecting repeated pulses of hydrogen peroxide solution at a pulse volume of less than 75 μL for evaporating the hydrogen peroxide solution. 
     
     
         11 . The method of  claim 10 , wherein the pulse volume is less than 35 μL. 
     
     
         12 . The method of  claim 11 , wherein the pulse volume is about 20 μL. 
     
     
         13 . The method of  claim 9 , wherein steps c) to h) are repeated at least once. 
     
     
         14 . The method of  claim 9 , wherein the first pressure is about 1 Torr. 
     
     
         15 . The method of  claim 9 , wherein the injecting of the gaseous conditioning agent is stopped when a second pressure of 17-54 Torr is reached. 
     
     
         16 . The method of  claim 15 , wherein the second pressure is about 20 Torr. 
     
     
         17 . The method of  claim 9 , wherein an amount of nitrogen oxide of 2 mg per liter of sterilization atmosphere is injected in the injecting step f. 
     
     
         18 . The method of  claim 9 , wherein after step c) removal of any component of the sterilization atmosphere is interrupted until the end of the second exposure period.