Sterilization method employing a circulating gaseous sterilant

• US 4,637,916 A
• Filed: 01/18/1984
• Issued: 01/20/1987
• Est. Priority Date: 01/28/1983
• Status: Expired due to Fees

• Current Assignee: Manufacture Belge de Gemblous SA, Université catholique de Louvain
• Original Assignee: Manufacture Belge de Gemblous SA, Université catholique de Louvain
• Inventors: Hennebert, Pierre, Roland, Michel, Gillard, Jean
• Primary Examiner(s): Lacey, David L.
• Assistant Examiner(s): Heaney, Brion P.
• Application Number:
  US06/571,765
• Time in Patent Office: 1,098 Days
• Field of Search: 422/27, 422/33, 422/34, 422/36, 422/295, 422/305, 422/306, 422/297
• US Class Current: 422/36
• CPC Class Codes: A61L 2/204 Formaldehyde

Abstract

A sterilization method comprising subjecting a sterilization chamber to an initial vacuum and then introducing steam to increase chamber pressure. The introduction of steam is interrupted and the chamber is brought into communication with a solution in a gaseous sterilant generator. The mixture of gaseous sterilant and chamber atmosphere are continuously circulated whereby equilibrium is established and the material to be sterilized is subject to constant temperature, pressure, sterilant concentration, and relative humidity for a period of time sufficient for sterilization. Also disclosed is an apparatus capable of performing the sterilization method comprising a sterilization chamber in combination with a gaseous sterilant generator. Formaldehyde is the preferred sterilizing agent.

Claims

1. A process for sterilizing a material or an article comprising the following steps in combination:

introducing the material or article to be sterilized into a chamber;

evacuating the chamber to a subatmospheric pressure;

admitting steam into the chamber to produce an increase in pressure until a temperature is attained within the chamber which is close to the desired sterilization temperature, while simultaneously maintaining a suction of steam and condensed water out of the chamber;

interrupting the admission of steam;

evacuating the chamber to a reduced pressure until the water which has condensed during the admission of steam has been removed;

bringing the chamber into communication with a gaseous phase containing formaldehyde to produce a gas mixture comprising the chamber atmosphere and the gaseous phase, said gaseous phase produced by evaporating an aqueous solution of formaldehyde which is kept at a constant temperature equal to the temperature desired for sterilization;

circulating the gas mixture from the chamber to the aqueous solution so that the gas mixture is continuously brought back into contact with the aqueous solution;

after the concentration of formaldehyde in the gas mixture has attained equilibrium with the aqueous solution, introducing a carrier gas into the chamber to increase pressure therein until a total pressure at about atmospheric pressure is produced and maintained therein;

exposing the surface of the material or article within the chamber for a time required to produce sterilization under the condition of constant temperature, pressure, formaldehyde concentration and relative humidity by continuing to keep the gas mixture in circulation and continuously bringing it back into contact with the aqueous solution, maintaining the pressure within the chamber at about atmospheric pressure, and maintaining the temperature of the gas mixture at the desired sterilization temperature;

cutting off communication between the aqueous solution and the gas mixture present in the chamber;

removing the formaldehyde present in the chamber by evacuation;

bringing the interior of the chamber back to atmospheric pressure by introduction of said carrier gas; and

withdrawing the material or article.

2. A process according to claim 1, characterized in that the sterilization temperature of the gas mixture is within the range of 20°

to 100°

C.

3. A process according to claim 1, wherein the carrier gas is selected from the group consisting of nitrogen, air or mixtures thereof.

4. A process according to claim 1 in which the aqueous solution of formaldehyde contains a polyol.

5. A process according to claim 4 in which the polyol is selected from the group consisting of glycerol, propylene glycol, ethylene glycol or polyoxyethylene glycol.

6. A process for sterilizing a material or an article comprising the following steps in combination:

introducing the material or article to be sterilized into a chamber;

evacuating the chamber to subatmospheric pressure;

admitting steam into the chamber to produce an increase in pressure until a temperature is attained within the chamber which is close to the desired sterilization temperature, while simultaneously maintaining a suction of steam and condensed water out of the chamber;

introducing a carrier gas at least once into the chamber to produce an increase in pressure, and after the at least one introduction of carrier gas, evacuating the chamber to a subatmospheric pressure which is less than that which was produced by introducing the carrier gas;

interrupting the admission of steam;

evacuating the chamber to a reduced pressure until the water which has condensed during the introduction of steam has been removed;

bringing the chamber into communication with a gaseous phase containing formaldehyde to produce a gas mixture comprising the chamber atmosphere and the gaseous phase, said gaseous phase produced by evaporating an aqueous solution of formaldehyde which is kept at a constant temperature equal to the temperature desired for sterilization;

circulating the gas mixture "present in the chamber and" has been replaced by from the chamber to the aqueous solution so that the gas mixture is continuously brought back into contact with the aqueous solution;

after the concentration of formaldehyde in the gas mixture has attained equilibrium with the aqueous solution, introducing a carrier gas into the chamber, to increase the pressure therein until a total pressure at about atmospheric pressure is produced and maintained therein;

exposing the surface of the material or article within the chamber for a time required to produce sterilization under the conditions of constant temperature, pressure, formaldehyde concentration and relative humidity by continuing to keep the gaseous phase in circulation and continuously bringing it back into contact with the aqueous solution, maintaining the pressure within the chamber at about atmospheric pressure, and maintaining the temperature of the gas mixture at the desired sterilization temperature;

cutting off communication between the aqueous solution and the gas mixture present in the chamber;

removing the formaldehyde present in the chamber by evacuation;

bringing the interior of the chamber back to atmospheric pressure by introduction of said carrier gas and

withdrawing the material or article.