Continuous-operation, closed loop decontamination system and method

• US 5,906,794 A
• Filed: 06/14/1996
• Issued: 05/25/1999
• Est. Priority Date: 06/15/1995
• Status: Expired due to Term

• Current Assignee: American Sterilizer Company (Steris Corporation)
• Original Assignee: American Sterilizer Company (Steris Corporation)
• Inventors: Childers, Robert W.
• Primary Examiner(s): Kemmerer, Elizabeth C.
• Assistant Examiner(s): Romeo, David S.
• Application Number:
  US08/664,980
• Time in Patent Office: 1,075 Days
• Field of Search: 422/292, 422/294, 422/299, 422/302, 422/307, 422/900, 422/905, 422/28, 422/30, 422/29, 422/174, 422/177, 422/305, 422/111, 219/430, 219/439
• US Class Current: 422/28
• CPC Class Codes: A61L 2/20 Gaseous substances, e.g. vapours
• CPC Class Codes: G05D 27/02 characterised by the use of electric means

Abstract

The invention provides an optimized method and system for conducting a continuous-operation, closed-loop, flow-through vapor phase decontamination. By the method, a liquid decontaminant is vaporized and delivered into, through and out of a sealable chamber by means of a carrier gas that is recirculated in a closed-loop conduit circuit. After leaving the chamber, the vapor is decomposed and the carrier gas is partially and selectively dried in response to the monitored temperature, relative humidity, and decontaminant vapor concentration in the chamber. The degree of drying is particularly selected in response to these chamber parameters to maintain a predetermined percent saturation of the decontaminant vapor in the chamber.

Claims

1. A closed-loop, flow through method of vapor phase decontamination in which a carrier gas is selectively and adjustably dried to varying amounts to maintain a predetermined humidity level within a sterilization chamber, which comprises the steps of:

providing a sealable chamber having an inlet port and an outlet port, and a closed-loop conduit circuit having a first end fluidly connected to the chamber inlet port and a second end fluidly connected to the chamber outlet port;

recirculating a flow of a carrier gas into, through, and out of the chamber and around the closed-loop conduit circuit;

delivering a vaporized decontaminant into the recirculating carrier gas flow upstream of the chamber inlet port;

converting the decontaminant vapor to a form suitable for disposal downstream of the chamber outlet port;

monitoring the chamber temperature, the chamber relative humidity, and the decontaminant vapor concentration in the chamber during decontamination;

selectively adjusting an amount of drying of the carrier gas entering the chamber in response to the monitored chamber temperature, chamber relative humidity, and decontaminant vapor concentration to a predetermined humidity level to maintain a predetermined percent saturation of the decontaminant vapor in the chamber during decontamination.

3. The method of claim 1, wherein the carrier gas is air.

4. The method of claim 1, wherein the vapor decontaminant comprises hydrogen peroxide.

5. The method of claim 4, wherein the converting step includes catalytically decomposing the hydrogen peroxide vapor into water and oxygen.

6. The method of claim 1, wherein the predetermined percent saturation ranges from about 85% to about 95%.

7. The method of claim 1, wherein the chamber temperature is monitored directly by sensing the read-out from a temperature sensor positioned in the chamber.

8. The method of claim 1, wherein the chamber relative humidity is monitored directly by sensing the read-out from a humidity sensor positioned in the chamber.

10. The method of claim 1, wherein the decontaminant vapor concentration is monitored indirectly and the monitoring step comprises monitoring the carrier gas flow rate and the delivery rate of the decontaminant vapor into the carrier gas.

2. A vapor phase decontamination method comprising:

circulating a flow of a carrier gas into, through, and out of a decontamination chamber;

selectively routing a first portion of the carrier gas flow discharged from the decontamination chamber through a dryer and selectively bypassing a second portion of the carrier gas flow around the dryer;

combining the first and second portions of the carrier gas flow;

entraining a decontaminant vapor into the combined carrier gas flow portions upstream of the decontamination chamber;

monitoring a temperature, a relative humidity, and a decontaminant vapor concentration in the decontamination chamber;

selectively adjusting the first portion of the carrier gas flow routed to the dryer relative to the second portion of the carrier gas flow bypassing the dryer in response to the monitored temperature, relative humidity, and decontaminant vapor concentration to control a percent saturation of the decontaminant vapor in the chamber.

9. A closed-loop, flow through method of vapor phase decontamination in a sealable chamber having an inlet port and an outlet port, and a closed-loop conduit circuit having a first end fluidly connected to the chamber inlet port and a second end fluidly connected to the chamber outlet port, the method comprising:

recirculating a flow of a carrier gas into, through, and out of the chamber and around the closed-loop conduit circuit;

entraining a decontaminant vapor into the recirculating carrier gas flow upstream of the chamber inlet port;

converting the decontaminant vapor to a form suitable for disposal downstream of the chamber outlet port;

monitoring temperature and decontaminant vapor concentration in the chamber during decontamination;

monitoring relative humidity of the carrier gas in the chamber indirectly by sensing a read-out from a humidity sensor positioned in the closed-loop conduit circuit downstream of the chamber outlet port;

adjusting a decree of drying the recirculating carrier gas flow in response to the monitored temperature, relative humidity, and decontaminant vapor concentration to maintain a selected percent saturation of the decontaminant vapor in the chamber during decontamination.

11. A closed-loop, flow-through vapor phase decontamination system comprising:

a sealable chamber having an inlet port and an outlet port;

a closed-loop conduit circuit having a first end fluidly connected to the chamber inlet port and a second end fluidly connected to the chamber outlet port for recirculating a carrier gas flow into, through, and out of the chamber;

a blowing unit fluidly connected to the conduit circuit to recirculate the carrier gas;

a drying unit fluidly connected to the conduit circuit for drying the carrier gas the drying unit being selectively controllable to adjust a decree to which humidity of the carrier gas is reduced;

a vaporizer unit fluidly connected to the conduit circuit between the drying unit and the chamber inlet port for delivering a decontaminant vapor into the recirculating carrier gas flow;

a converter for converting the decontaminant vapor to a form suitable for disposal, fluidly connected to the conduit circuit downstream of the chamber outlet port;

a processing unit for monitoring instantaneous temperature, relative humidity, and decontaminant vapor concentration, and for controlling the adjustable drying unit to adjust the degree of drying of the carrier gas in accordance with the monitored temperature, relative humidity, and concentration to maintain a predetermined percent saturation of the decontaminant vapor in the chamber during decontamination even as any of the temperature, relative humidity, and concentration in the chamber varies.

12. The system of claim 11, wherein the drying unit comprises:

an adjustable proportioning valve having a first flow path and a second flow path through which adjustable portions of the recirculating carrier gas are passed,

a regenerative driving agent positioned downstream of the proportioning valve and having an inlet port and an outlet port,

a first flow line fluidly connecting the first flow path to the regenerative driving agent inlet port, and

a second flow line fluidly connecting the second flow path to the conduit circuit between the regenerative drying agent and the vaporizer unit and bypassing the air dryer.

13. The system of claim 11, wherein the blowing unit comprises a first air blower positioned upstream of the drying unit and a second air blower positioned downstream of the drying unit.

14. The system of claim 11, wherein the processing unit comprises a temperature sensor positioned in the chamber.

15. The system of claim 11, wherein the processing unit comprises a relative humidity sensor positioned in the chamber.

16. The system of claim 11, wherein the processing unit comprises a sensor for indicating the absolute humidity of the carrier gas flow exiting the outlet port of the chamber.

17. The system of claim 11, wherein the processing unit comprises a flow meter for the carrier gas and means for determining the delivery rate of the decontaminant vapor into the carrier gas.

18. The system of claim 11, wherein the decontaminant vapor is hydrogen peroxide and the converter comprises a catalytic converter for decomposing hydrogen peroxide to water and oxygen.