Method and apparatus for decontaminating a region without dehumidification

• US 8,007,717 B2
• Filed: 08/14/2007
• Issued: 08/30/2011
• Est. Priority Date: 08/14/2007
• Status: Active Grant

• Current Assignee: American Sterilizer Company (Steris Corporation)
• Original Assignee: American Sterilizer Company (Steris Corporation)
• Inventors: Hill, Aaron L.
• Primary Examiner(s): CONLEY, SEAN EVERETT
• Application Number:
  US11/838,327
• Publication Number:
  US 20090047174A1
• Time in Patent Office: 1,477 Days
• Field of Search: 422/3, 422/28, 422/37, 422/105, 422/108, 422/292, 422/298
• US Class Current: 422/3
• CPC Class Codes: A61L 2/208 Hydrogen peroxide

Abstract

A method and apparatus for decontaminating a region with a gaseous or vaporous decontaminant (e.g., vaporized hydrogen peroxide) without dehumidification (e.g., without the use of a dryer). The saturation concentration of the decontaminant inside the region is monitored, and the concentration of the decontaminant inside the region is regulated to prevent condensation of the decontaminant. The bioburden reduction is continuously monitored during a decontamination phase to ascertain successful completion of a decontamination process in accordance with a target bioburden reduction.

Claims

1. A method for decontaminating a region with a vaporized decontaminant, the method comprising the steps of:

supplying vaporized decontaminant into the region for obtaining at least a minimum concentration level of the vaporized decontaminant in the region;

monitoring the concentration of the vaporized decontaminant in the region;

determining the dew point concentration of the vaporized decontaminant in the region;

regulating the supply of vaporized decontaminant into the region to maintain the concentration of vaporized decontaminant to at least a predetermined amount below the dew point concentration of the vaporized decontaminant;

determining a bioburden reduction for each of one or more time increments of a decontamination process, wherein determining said bioburden reduction for each time increment includes;

establishing an initial bioburden within the region;

determining a D-value associated with the concentration of vaporized decontaminant within the region, wherein said D-value is a time required for a 1 log reduction in bioburden; and

calculating a bioburden within the region in accordance with the initial bioburden, the time increment and the D-value;

calculating a total bioburden reduction within the region by summing said bioburden reduction determined for each of said one or more time increments;

determining whether a decontamination process is complete by comparing the total bioburden reduction within the region to a target bioburden reduction; and

continuing the decontamination process for at least one additional time increment until the total bioburden reduction within the region has achieved the target bioburden reduction.

2. A method according to claim 1, wherein determining said bioburden reduction for each time increment further comprises:

comparing the initial bioburden with the calculated bioburden.

3. A method according to claim 1, wherein said vaporized decontaminant is vaporized hydrogen peroxide.

4. A vapor decontamination system for decontaminating a region, said system comprising:

a decontaminant supply for providing a supply of liquid decontaminant;

a vaporizer for generating a vaporized decontaminant, said vaporizer receiving liquid decontaminant from the decontaminant supply;

a circulating system for supplying said vaporized decontaminant to said region; and

control means programmed to;

monitor the concentration of the vaporized decontaminant in the region;

determine the dew point concentration of the vaporized decontaminant in the region;

regulate the supply of vaporized decontaminant into the region to maintain the concentration of vaporized decontaminant at least a predetermined amount below the dew point concentration of the vaporized decontaminant;

determine a bioburden reduction for each of one or more time increments of a decontamination process, wherein said control means is programmed to determine said bioburden reduction for each time increment by;

establishing an initial bioburden within the region;

determining a D-value associated with the concentration of vaporized decontaminant within the region, wherein said D-value is a time required for a 1 log reduction in bioburden; and

calculating a bioburden within the region in accordance with the initial bioburden, the time increment and the D-value;

calculate a total bioburden reduction within the region by summing said bioburden reduction for each of said one or more time increments; and

determine whether a decontamination process is complete by comparing the total bioburden reduction within the region to a target bioburden reduction, wherein the decontamination process is continued for at least one additional time increment until the total bioburden reduction within the region has achieved the target bioburden reduction.

5. A vapor decontamination system according to claim 4, wherein said system further comprises:

at least one humidity sensor providing a first signal indicative of moisture in the region;

a temperature sensor providing a second signal indicative of the temperature in the region; and

at least one concentration sensor providing a third signal indicative of the concentration of the decontaminant in the region.

6. A vapor decontamination system according to claim 4, wherein said control means is programmed to determine said bioburden reduction for each time increment by:

comparing the initial bioburden with the calculated bioburden.

7. A vapor decontamination system according to claim 4, wherein said vaporized decontaminant is vaporized hydrogen peroxide.

8. A method for decontaminating a region with vaporized hydrogen peroxide, the method comprising the steps of:

supplying vaporized hydrogen peroxide into the region;

monitoring the concentration of the vaporized hydrogen peroxide in the region;

regulating the supply of vaporized hydrogen peroxide into the region to maintain the concentration of vaporized hydrogen peroxide below the dew point concentration of the vaporized hydrogen peroxide;

determining a bioburden reduction for each of one or more time increments of a decontamination process, wherein determining said bioburden reduction for each of said one or more time increments includes;

establishing an initial bioburden within the region;

determining a D-value associated with the concentration of vaporized decontaminant within the region, wherein said D-value is a time required for a 1 log reduction in bioburden; and

calculating a bioburden within the region in accordance with the initial bioburden, the time period and the D-value;

repeatedly calculating a total bioburden reduction within the region during the decontamination process in accordance with the bioburden reduction determined for each of said plurality of time increments, said total bioburden reduction calculated at the completion of each time increment of the decontamination process;

determining whether the decontamination process is complete by comparing the calculated total bioburden reduction to a target bioburden reduction; and

continuing the decontamination process until the calculated total bioburden reduction within the region has achieved the target bioburden reduction.

9. A method according to claim 8, wherein said total bioburden reduction within the region is calculated by summing said bioburden reduction for each of said one or more time increments of the decontamination process.

10. A method according to claim 8, wherein determining said bioburden reduction for each of said time increments further comprises:

comparing the initial bioburden with the calculated bioburden.

11. A method for decontaminating a region with a vaporized decontaminant, the method comprising the steps of:

supplying vaporized decontaminant into the region;

monitoring at least one parameter influencing the dew point concentration of the vaporized decontaminant in the region;

regulating the supply of vaporized decontaminant introduced into the region to maintain the concentration of vaporized decontaminant within the region at a level below the dew point concentration of the vaporized decontaminant;

determining a bioburden reduction for each of one or more time increments of a decontamination process, wherein determining said bioburden reduction for each time increment includes;

establishing an initial bioburden within the region;

determining a D-value associated with the concentration of vaporized decontaminant within the region, wherein said D-value is a time required for a 1 log reduction in bioburden; and

calculating a bioburden within the region in accordance with the initial bioburden, the time increment and the D-value;

calculating a total bioburden reduction within the region by summing said bioburden reduction determined for each of said one or more time increments; and

continuing a decontamination process for at least one additional time increment until the total bioburden reduction within the region has at least achieved a target bioburden reduction.

12. A method according to claim 11, wherein said at least one parameter includes humidity level within said region.

13. A method according to claim 11, wherein said at least one parameter includes temperature within said region.

14. A method according to claim 11, wherein said step of calculating the total bioburden reduction within the region includes determining a bioburden reduction for one or more time increments.

15. A method according to claim 14, wherein said bioburden reduction for each of said time increments is summed to obtain the total bioburden reduction within the region.

16. A method according to claim 11, wherein determining said bioburden reduction for each time increment further comprises:

comparing the initial bioburden with the calculated bioburden.

17. A method according to claim 11, wherein said vaporized decontaminant is vaporized hydrogen peroxide.

18. A vapor decontamination system for decontaminating a region, said system comprising:

a vaporizer for generating a vaporized decontaminant, said generator receiving liquid decontaminant from the decontaminant supply;

a circulating system for supplying said vaporized decontaminant to said region; and

control means programmed to;

monitor at least one parameter influencing the dew point concentration of the vaporized decontaminant in the region;

regulate the supply of vaporized decontaminant introduced into the region to maintain the concentration of vaporized decontaminant within the region at a level below the dew point concentration of the vaporized decontaminant;

determine a bioburden reduction for each of one or more time increments of a decontamination process, wherein said bioburden reduction for each time increment is determined according to a D-value and initial bioburden within the region, said D-value determined as a function of concentration of the vaporized decontaminant within the region, wherein said D-value is a time required for a 1 log reduction in bioburden;

calculate a total bioburden reduction within the region by summing said bioburden reduction determined for each of said one or more time increments; and

continue a decontamination process for at least one additional time increment until the total bioburden reduction within the region has at least achieved a target bioburden reduction.

19. A vapor decontamination system according to claim 18, wherein said at least one parameter includes humidity level within said region.

20. A vapor decontamination system according to claim 18, wherein said at least one parameter includes temperature within said region.