Sterilization method and apparatus
View Patent ↗A method of sterilizing an article by sequentially exposing the article to hydrogen peroxide and ozone is disclosed. The article is exposed under vacuum first to an evaporated aqueous solution of hydrogen peroxide and subsequently to an ozone containing gas. The exposure is carried out without reducing the water vapor content of the sterilization atmosphere, the water vapor content being derived from the aqueous solvent of the hydrogen peroxide solution and from the decomposition of the hydrogen peroxide into water and oxygen. The complete sterilization process is carried out while the chamber remains sealed and without removal of any component of the sterilization atmosphere. For this purpose, the chamber is initially evacuated to a first vacuum pressure sufficient to cause evaporation of the aqueous hydrogen peroxide at the temperature of the chamber atmosphere. The chamber is then sealed for the remainder of the sterilization process and during all sterilant injection cycles. Keeping the chamber sealed and maintaining the hydrogen peroxide and its decomposition products in the chamber for the subsequent ozone sterilization step 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 hydrogen peroxide and ozone in combination.
1. 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 chamber,
c. applying to the chamber a vacuum of a first pressure, the first pressure being sufficient to evaporate an aqueous solution of hydrogen peroxide, at the temperature of an atmosphere in the chamber, to form a water vapor component and a hydrogen peroxide vapor component,
d. interrupting all removal of any component of the chamber atmosphere after applying the vacuum at least until the end of a second exposure period,
e. during a first exposure period, humidifying the chamber atmosphere solely by injecting repeated pulses of evaporated aqueous hydrogen peroxide solution, having a first hydrogen peroxide concentration, into the sealed chamber at a pulse volume of at most 75 μl, and terminating the injecting once a preselected second pressure, higher than the first pressure and in the range of 17-54 Torr, is reached in the sealed sterilization chamber to create on the article a layer of micro-condensation of hydrogen peroxide with a second hydrogen peroxide concentration higher than the first concentration;
f. during the second exposure period following the first exposure period, injecting into the chamber a dry ozone or nitric oxide containing gas, whereby the humidifying of the chamber atmosphere improves a sterilization efficiency of the dry ozone or nitric oxide containing gas to achieve sterilization of the article;
g. removing residual hydrogen peroxide, ozone, or nitric oxide containing gas from the chamber at the end of the second exposure period, and
h. removing the article from the chamber.
2. The method of claim 1 , wherein the pulse volume is less than 35 μL.
3. The method of claim 2 , wherein the pulse volume is about 20 μL.
4. The method of claim 1 , wherein steps c) to g are repeated at least once.
5. The method of claim 1 , wherein the solution is a 50% hydrogen peroxide solution and the second pressure is 20 Torr.
6. The method of claim 1 , wherein an amount of ozone in the range of 1-10 mg per liter of sterilization atmosphere is injected in the injecting step f).
7. The method of claim 1 , wherein the first pressure is 1 Torr (1.33 mbar).
8. The method of claim 1 , wherein the second pressure is 20 Torr.
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 chamber,
c. applying to the chamber a vacuum of a first pressure, the first pressure being sufficient to evaporate an aqueous solution of hydrogen peroxide, at the temperature of an atmosphere in the chamber, to form a water vapor component and a hydrogen peroxide vapor component, the aqueous solution having a first hydrogen peroxide concentration,
d. interrupting all removal of any component of the chamber atmosphere after applying the vacuum at least until the end of a second exposure period,
e. during a first exposure period, humidifying the chamber atmosphere solely by injecting into the sealed chamber repeated pulses of the evaporated aqueous hydrogen peroxide solution at a pulse volume of at most 75 μl, and terminating the injecting once a preselected second pressure, higher than the first pressure, is reached in the sealed sterilization chamber for controlling selective condensation of the hydrogen peroxide vapor component and to create a layer of micro-condensation of hydrogen peroxide on the article with a second hydrogen peroxide concentration higher than the first concentration;
f. during the second exposure period following the first exposure period, injecting a dry ozone or nitric oxide containing gas into the chamber, whereby the humidifying of the chamber atmosphere improves a sterilization efficiency of the dry ozone or nitric oxide containing gas to achieve sterilization of the article;
g. removing residual hydrogen peroxide, ozone, or nitric oxide containing gas from the chamber at the end of the second exposure period, and
h. removing the article from the chamber.
10. 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 chamber,
c. applying to the chamber a vacuum of a first pressure, the first pressure being sufficient to evaporate an aqueous solution of hydrogen peroxide, at the temperature of an atmosphere in the chamber, to form a water vapor component and a hydrogen peroxide vapor component, the aqueous solution having a first hydrogen peroxide concentration,
d. interrupting all removal of any component of the chamber atmosphere after applying the vacuum at least until the end of a second exposure period,
e. during a first exposure period, humidifying the chamber atmosphere solely by injecting into the sealed chamber repeated pulses of the evaporated aqueous hydrogen peroxide solution, and terminating the injecting once a preselected second pressure, higher than the first pressure, is reached in the sealed sterilization chamber, the pulses having a volume selected for controlling selective condensation of the hydrogen peroxide vapor component to create a layer of micro-condensation of hydrogen peroxide on the article with a second hydrogen peroxide concentration higher than the first concentration and to prevent condensation at an injection site of the evaporated aqueous hydrogen peroxide solution;
f. during the second exposure period following the first exposure period, injecting a dry ozone or nitric oxide containing gas into the chamber, whereby the humidifying of the chamber atmosphere improves a sterilization efficiency of the dry ozone or nitric oxide containing gas to achieve sterilization of the article;
g. removing residual hydrogen peroxide, ozone, or nitric oxide containing gas from the chamber at the end of the second exposure period, and
h. removing the article from the chamber.