Gas sterilization

Chemical apparatus and process disinfecting – deodorizing – preser – Process disinfecting – preserving – deodorizing – or sterilizing – Using direct contact with electrical or electromagnetic...

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422 22, A61L 200

Patent

active

055122442

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to the sterilisation of medical and other equipment by means of chemically active gaseous media.
A proposed technique for sterilising medical equipment, and other objects, is to expose them to the action of a plasma. Plasmas in this context are gaseous media which contain a significant proportion of ionised species and free electrons. Examples of methods of carrying out this technique are disclosed in U.S. Pat. Nos. 3,383,163; 3,851,436; 3,948,601; 4,207,286; 4,321,232; 4,348,357; 4,643,876; Japanese Application Disclosure numbers 103460/83; 162276/83 and European Patent Application number 387022A. However, gas plasmas, although effective as sterilising agents have been found often to be too chemically aggressive, causing damage to an object being sterilised. This failing has been an inhibiting factor in the general adoption of the technique.
It is an object of the present invention to provide a method of sterilising objects by means of activated gaseous media, that is to say, gaseous media which contain significant numbers of free radicals, metastable and electronically excited species, but which do not contain significant amounts of ionised species.
According to the present invention there is provided a method of sterilising articles by exposing them to a biologically active gaseous medium, wherein there is included the operations of activating a gaseous medium to provide free radicals, and/or electronicaly and/or vibrationally excited species, ensuring that the activated gaseous medium is substantially free of charged species and exposing the article to be sterilised to the charged species free activated gaseous medium for a period sufficient to ensure that the article is sterilised.
Ionised species produced in the activation process are allowed to recombine before reaching the sterilisation chamber so that only the neutral activated gas is applied to the object to be sterilised.
The dissociation and/or electronic excitation of the gaseous medium can be achieved by means of bombardment with energetic particles, the application of DC and varying electric fields, chemically, or photo-electrically by means of electromagnetic radiation including both c.w. and high power pulsed RF and microwaves and laser radiation.
Short pulse, high power microwaves produced at a high repetition frequency are particularly effective in achieving significant dissociation whilst minimising thermal effects.
Preferably, the gaseous medium includes activating agents which increase the population of the activated species in the afterglow from the activation process. Suitable activating agents are: SF.sub.6 ; H.sub.2 O; O.sub.2 ; H.sub.2 S; CO; C.sub.2 H.sub.2 ; CH.sub.4 ; Hg; NH.sub.3 ; Cl.sub.2 ; N.sub.2 O; NO; C.sub.2 H.sub.6 or mixtures thereof.
An activating agent can work by enhancing dissociation, enhancing or inhibiting recombination or by surface modification in a discharge chamber. It can form a component of the activated gas and can be added before or after the activating discharge.
A suitable gaseous medium for use in carrying out the present invention comprises 41%-89% by volume oxygen with the balance made up by argon, helium or nitrogen, or mixtures thereof and/or up to 9% by volume of an activating agent which can be H.sub.2 O; N.sub.2 O; H.sub.2 ; N.sub.2 ; NH.sub.3 or NO, or mixtures thereof.
A second suitable gaseous medium for carrying out the present invention comprises 30%-99.9% nitrogen with 0.1%-9% by volume of an activating agent which can be SF.sub.6 ; H.sub.2 O; Cl.sub.2 ; NO; O.sub.2 ; H; CO.sub.2 ; CO; C.sub.2 H.sub.2 ; C.sub.2 H.sub.6 ; CH.sub.4 ; NH.sub.3 ; NF.sub.3 or mixtures thereof, the balance being made up by argon or helium.
A third suitable gaseous medium for carrying out the invention comprises 1%-99%, oxygen with 0.1%-9% by volume of an activating agent such as H.sub.2 O; N.sub.2 O; NH.sub.3, H.sub.2, N.sub.2 or NO, the balance being made up by argon or helium.
A fourth suitable gaseous medium is ammonia (NH.sub.3) containing up to 9% by volume of an activating

REFERENCES:
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