Patent Abstract:
A flash sterilization container( 10 ) comprises a pan( 12 ) forming the bottom of the container holding a tray ( 14 ), with a cover ( 16 ) forming the top of the container, and a filter element ( 20 ). The filter ( 20 ) covers an opening in the cover ( 16 ) so that the inside of the container ( 10 ) formed when the cover is removably sealed to the pan ( 12 ) can communicate with the atmosphere surrounding the sealed container allowing steam to enter and exit the container passing through the filter ( 20 ). Items to be sterilized are placed on the tray ( 14 ) and the cover ( 16 ) is attached and sealed to the pan ( 12 ). The sealed container is then placed in an autoclave or other source of pressurized steam. The filter is composed of a material which will allow the pressurized steam to pass through but which is relatively impervious to dust and microorganisms thereby maintaining the sterility of the interior of the container and its contents.

Full Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of our co-pending U.S. application Ser. No. 09/023,055 filed on Feb. 12. 1998, now U.S. Pat. No. 5,968,459, the entire contents and substance of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates, in general, to a method for sterilizing medical instruments with steam and, in particular, to a sterilization container useful for flash sterilization and gas plasma sterilization, which includes a filter that permits maximum steam or gas sterilant penetration and prevents microorganisms and dust from entering. 
     2. Description of Related Art 
     Steam sterilization is a common method used for the sterilization of items, especially medical instruments by processing the items in an autoclave and exposing them to high-pressure steam. This method requires the wrapping of individual items, heating the items with steam and then waiting for a drying/cooling period. Often during surgical procedures commonly used instruments need to be quickly sterilized after use or inadvertent contamination. Under such circumstances the standard autoclave method would take too long. An alternative sterilization method which can be used under these circumstances, is known as flash sterilization. In flash sterilization metal instruments are not wrapped but are heated directly by the steam allowing sterilization in a reduced period of time. One drawback to the use of flash sterilization is the lack of a drying period. When the items are still moist and hot from sterilization. microorganisms and dust can contaminate the items when they are transported from the autoclave/sterilizer. Nevertheless, flash sterilization results in reduced exposure time. 
     One common design for containers for flash sterilization is described in U.S. Pat. Nos. 5,097,865 and 4,748,003. Such containers use valves which require greater than atmospheric pressures to open the valves and allow the high-pressure steam to enter the container but are closed under normal pressure conditions. This approach has a number of disadvantages. Such containers must be opened to allow the steam to escape, thus breaking the sterile field. Even if kept sealed, these containers cannot maintain the sterile field for longer than 24 hours. Also, the high temperature, high pressure valves needed for this method are very complex and very expensive. In addition, such containers do not provide an indication as to whether or not the valve properly functioned to allow the high pressure steam to enter the container. 
     The present invention facilitates the use of flash sterilization while retaining the advantage of standard autoclave sterilization by maintaining the sterility of the items in the sterilization container. Instead of a costly, complicated valve system the present invention uses a passive filter system which is capable of allowing steam to enter and exit the container and still keep microorganisms and dust out, maintaining the sterile field in the container for long term storage. The present invention, especially in the mid-size container, provides the additional advantage of reducing the time required for steam sterilization. 
     In addition to flash steam sterilization the industry is beginning to use gas plasma as an alternative. One commercially available gas plasma system is sold as STERRAD® by Advanced Sterilization Products, a division of the Johnson &amp; Johnson Company. Gas plasma has known advantages over steam sterilization, including sterilizing at a lower temperature than required for steam sterilization, which is beneficial when sterilizing temperature-sensitive devices. However, it has been learned that frequently the sterilizing gas plasma does not reach all important surfaces on the inside of the sterilization container, especially where long tubular instruments or cables are contained. Accordingly, there are believed to be very few, if any, sterilization containers approved for use with gas plasma, especially in the mid-size range. Clearly a technique is missing in the prior art to guarantee satisfactory circulation of gas plasma within a sterilization container, especially where it is critical to reach the edges and corners of the interior of the sterilization container and to penetrate internal components such as laparascopic guides and tubing. The present invention, however, maintains its efficacy when utilized with gas plasma as the sterilant. 
     SUMMARY OF THE INVENTION 
     Briefly described, the invention comprises a sterilization container and a flash sterilization method for sterilizing items, which allow for extended, sterile storage of the sterilized items. The flash sterilization method uses a sterilization container having a pan, a cover and one or more filters for preventing dust and microorganisms from entering the container and contaminating the sterilized items while still allowing steam or gas plasma in and out of the container during the sterilization process. These containers can be used in the flash sterilization process commonly used in surgical theaters. The filter can be permanently mounted in the container or can be removable for replacement with new or different types of filters. Removable filters will allow for the retrofitting of currently used containers with the filters so that new containers do not need to be purchased to take advantage of the filtered flash sterilization method of the present invention. The filter can be removably attached to the container, manufactured as an integral part of the container, or incorporated into a self-contained removable filter unit. 
     Another aspect of the present invention comprises a novel filter retainer used for attaching a filter to the sterilization container. The filter retainer has a plurality of steam penetration holes which can be of various sizes and shapes allowing sufficient steam to enter the container. The filter retainer also comprises one or more gaskets for maintaining a seal between the filter retainer and the sterilization container as well as a locking means for removably attaching the retainer to the container. 
     Another alternative embodiment of the invention provides for a single set of vent holes in the center of the lid, or cover, of the container and two sets of vent holes, arranged in a circular fashion, located in the base of the pan or bottom of the container. The second and third sets of vent holes in the base are located on opposite sides of the minor axis center line of the base in such a way that they do not overlap. Gas plasma passing through the first set of vent holes in the lid is then forced to travel to the extremes of the container in order to be exhausted thereby guaranteeing that all parts of the tray or sterilizable instruments on the inside come into contact with the gas plasma as well as the edges and corners and interior of the container. 
     According to yet another embodiment of the invention, a pair of vent means, comprising a first and fourth set, are located in the lid in a manner similar to the way the second and third set of vent holes are located in the base. This also helps to guarantee thorough circulation of the gas plasma within the container. These two improvements are especially suited for use with mid-size sterilizable containers that employ gas plasma as the sterilizing agent. This invention, however, enhances the efficacy of all methods of sterilization, including steam sterilization and gas plasma sterilization. The first, second, third and fourth sets of vent holes are preferably each arranged in four concentric circles having the holes on their circumference. Other alternative symmetrical patterns, like square, would also be acceptable. The keeper plate on the bottom of the container preferably includes a similar set of holes, but offset so that there can be no “strikethrough” of sharp objects through the filter underneath the series of vent holes but above the keeper plate. 
     These and other features of the invention may be more fully understood by reference to the following drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a perspective view of the preferred embodiment of the flash sterilization container invention. 
     FIG. 1B is a top perspective view of the flash sterilization container cover with a filter retainer. 
     FIG. 1C is a perspective view of the flash sterilization container invention with the top surface of the lid having a D-ring attached to it. 
     FIG. 2A is an exploded perspective view of the flash sterilization container filter invention. 
     FIG. 2B is a partial view of a cover opening configuration. 
     FIG. 3A is a side elevational view of the filter retainer invention. 
     FIG. 3B is a top plan view of the filter retainer invention with the locking means in the locked position. 
     FIG. 3C is a top plan view of the filter retainer invention with the locking means in the unlocked position. 
     FIG. 4A is a partial, side elevational view of a flash sterilization container cover with an incorporated filter. 
     FIG. 4B is a partial, side elevational view of a flash sterilization container and a filter cartridge. 
     FIG. 5A is an exploded view of an alternative embodiment of the invention especially suitable for use with gas plasma in which the base of the container includes two sets of circular vent holes located on opposite sides of the center line of the minor axis of the container. 
     FIG. 5B is a top plan view of the lid of the alternative embodiment illustrated in FIG.  5 A. 
     FIG. 5C is an elevational cross-sectional view of the lid illustrated in FIG.  5 B. 
     FIG. 5D is a partial, cross-sectional exploded view of the top, or first set, of circular vent means illustrated in a manner in which the pull ring is attached to the lid. 
     FIG. 5E is a detailed, cross-sectional end view of the lid of FIG. 5B illustrated in a manner in which the snap-on post attaches to the filter retainer plate. 
     FIG. 5F illustrates the bottom, or pan, of the gas plasma alternative embodiment illustrating how the second and third set of circular vent means are located on opposite sides of the center line of the minor axis of the bottom portion. 
     FIG. 6A is an exploded view of another alternative embodiment of the gas plasma container illustrating a fourth set of circular vent means located adjacent to said first set of circular vent means in the top of lid of the container. 
     FIG. 6B is a top plan view of the lid of the alternative embodiment illustrated in FIG.  6 A. 
     FIG. 6C is a side elevational cross-sectional view of the lid illustrated in FIG.  6 B. 
     FIG. 6D is a partial, detail exploded view of the first set of circular vent means illustrating the manner in which the pull ring is attached to the lid. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     During the course of this description like numbers will be used to identify like elements according to the different figures that illustrate the invention. 
     The flash sterilization container invention  10  according to a preferred embodiment thereof is illustrated in FIG. 1. A sterilization container  10  comprises a pan  12 , which forms the bottom of the container that holds and supports a conventional sterilizable tray  14 , and a cover  16 , which forms the top of the container. The cover is removably attached to the pan to form a hermetically sealed container. This can be accomplished by conventional means such as hinges and clamps and a sealing gasket. The cover  16  is provided with an opening  18  at its top. This opening  18  is covered with a filter  20  to allow steam to enter and exit the container through the opening by passing through the filter. The filter can be removably or permanently attached to the cover. This filter is made of a material, or combination of materials, such that the filter is permeable to the flow of steam but will inhibit dust or other airborne particles or microorganisms from passing through. Examples of such materials include paper. TEFLON®, a registered trademark of E.I. Du Pond de Nemours and Co. Inc., porous stainless steel. polysulfone, and hydrophobic material, such as GORTEX®, a registered trademark of W. L. Gore &amp; Associates, and Kimguard®, a trademark of the Kimberly-Clark Corporation. The filter is attached to the cover by means which will prevent any steam, dust or other airborne particles or microorganisms from passing through the opening in the cover without passing through the filter. 
     In the preferred embodiment, the filter  20  is placed over the opening  18  in the top of the cover  16  and the filter is attached to the cover by a filter retainer  30 . The preferred embodiment of such a filter retainer is illustrated in FIGS. 1A,  1 B,  2 A,  3 A and  3 B. The filter retainer  30  comprises a filter retainer disc  32  and a means for sealing the filter retainer disc to the cover. The filter retainer disc has an inner disc  34 , a middle ring  36 , and an outer ring  38 . The middle ring  36  has a plurality of holes  40  to allow the flow of steam through the filter retainer disc  32 , through the filter  20 , and through the opening  18  in the cover  16 . The filter retainer can have one or more sealing means for forming a seal between the filter and the cover. The outer ring  38  has a means for forming a seal between the filter and the cover. In one embodiment the outer ring has an inverted-u shaped cross-section. A gasket  46  is placed in the inverted-U outer ring and can be made of silicone, neoprene, TEFLON®, a registered trademark of E.I. Du Pond de Nemours and Co. Inc., or any other suitable material. Inner disc  34  may also have a sealing means if necessary, such as a gasket  48 . 
     The preferred embodiment of a means for attaching the filter retainer to the cover is illustrated in FIGS. 1A,  1 B,  2 A,  3 A, and  3 B. Pin  50  extends upwards from the top surface of the cover  16 . Inner disc  34  of the filter retainer disc  32  has a hole  42  for accepting pin  50 . Pin  50  has sufficient length to extend past the top surface of the filter retainer  30  when the filter retainer is placed on the cover  16  allowing the hole in the inner disc  42  to engage the pin  50 . Pin  50  is preferably located in the center of the opening  18  in the cover  16 . To locate the pin in the proper position, the opening in the cover can be, for example, a circular opening with cross pieces such as those illustrated in FIG.  2 A. In an alternate embodiment, the opening in the cover can be comprised of a multiplicity of smaller openings in the cover, as depicted in FIG. 2B. A locking means is located on the inner disc which engages the pin  50  and holds the filter retainer in place. 
     The preferred locking means is comprised of a sliding plate  60  which is movably attached to the inner disc  34  of the filter retainer disc  32  with a hinge pin  62  extending from the inner disc  34  of the filter retainer disc  32 , so that the sliding plate  60  rotates about the center of the hinge pin  62  while remaining in contact with the inner disc. The sliding plate  60  has an arc-shaped pin slot  64  having an effective radius equal to the distance from the hinge pin  62  to the hole in the center of the inner disc  42 , whereby the center of the hole in the inner disc maintains alignment with the center of the arc-shaped slot throughout the rotation of the sliding plate. 
     The retainer pin  50  is comprised of a cylindrical body  52  having opposite ends and an outside diameter essentially equal to the inside diameter of the hole  42  in the filter retainer disc, a cylindrical neck  54  having a diameter smaller than the diameter of the body and equal to the width of the arc shaped slot  64 , and a cylindrical head  56  having a top and a bottom and having a diameter larger than the pin neck  54 , preferably equal to the diameter of the pin body  52 . One end of the pin body  52  is attached to the cover  16  by conventional means, such as, a rivet  58 , a screw, a thread, or a spot weld. Pin neck  54  is attached to the end of the pin body  52  opposite the attachment to the cover. The bottom of the pin head is attached to the pin neck at the end opposite the pin neck&#39;s attachment to the pin body. The retainer pin can be made of separate elements attached by conventional means or preferably manufactured from a single piece of stock. The length of the pin body is essentially equal to the distance from the top surface of the cover to the top surface of the inner disc. The length of the pin neck is at least equal to the thickness of the sliding plate. The combined length of the pin body and pin neck is such that the bottom of the pin head is slightly lower than the top surface of the sliding plate  60  so that when the arc-shaped pin slot  64  engages the pin neck  54 , the filter retainer disc  32  will be forced toward the cover, compressing the gaskets  46 ,  48 , and creating a seal between the filter retainer  30  and the cover  16 . The top of the pin head  56  can have a taper to facilitate the insertion of the retainer pin  50  through the hole in the filter retainer disc  42  and arc-shaped slot in the sliding plate  64 . 
     The arc shaped slot  64  has a width essentially equal to the outside diameter of to the pin neck and a length at least twice as long as the outside diameter of the pin head. At one end of the arc-shaped slot  64 , the width of the slot is increased to allow the pin head to pass through the arc-shaped slot. 
     A filter is attached to the cover with the filter retainer by placing a filter  20  over the hole  18  in the cover  16 , the sliding plate  60  is positioned so that the end of the arc-shaped slot  64  having an increased width is aligned with the hole in the inner disc  42 , the filter retainer  30  is then placed over the opening in the cover  16  so that the retainer pin  50  passes through the hole in the inner disc  42  and the enlarged end of the arc-shaped slot  64 , and the sliding plate  60  is then rotated so that the arc-shaped slot  64  engages the pin neck  54 , thereby preventing the pin from passing back through the arc-shaped slot and thus attaching the filter retainer to the cover. 
     In a preferred embodiment, the filter retainer  30  has a means for limiting the rotation of the sliding plate  60  and facilitating the positioning of the sliding plate in an “open” position, where the enlarged end of the arc-shaped slot  64  lines up with the hole in the inner disc  42 , and a “locked” position, where the opposite end of the arc-shaped slot lines up with the hole in the inner disc. One embodiment of a limiting means incorporates an arc-shaped limiting slot  66  on the sliding plate  60 . The arc of the limiting slot  66  is parallel to the arc of the arc-shaped slot  64  and has an effective radius larger than the radius of the arc-shaped slot  64 . A locating pin  68  is attached to, and extends from, the inner disc  34  such that it engages one end of the limiting slot  66  when the sliding plate  60  is in the locked position and engages the opposite end of the arc-shaped slot when the sliding plate is in the unlocked position. The locating pin  68  is preferably hemispherical-shaped to facilitate the movement of the sliding plate  60  over the locating pin  68 . A hemispherical locating pin  68  can be made, for example, by inserting and attaching a ball bearing in a hole in the inner disc  34 . The width of the limiting slot  66  is slightly less than the diameter of the locating pin  68 . The width of the limiting slot  66  at each of the two, opposite ends, is enlarged slightly, forming two holes each having a diameter slightly larger than the diameter of the locating pin  68 . Consequently, the sliding plate  60  is held in the locked and open positions when the locating pin  68  engages each of the holes in the ends of the limiting slot  66 , requiring the application of an external force to move the sliding plate between the two positions. 
     The sliding plate  60  preferably has a handle  70  to facilitate moving the plate between the open and closed positions. The handle  70  preferably extends parallel to the plane of the sliding plate. The handle  70  can be attached to the sliding plate or manufactured with the sliding plate as a single piece. 
     As described above, the preferred embodiment comprises a sterilization container having a filter retainer mechanism. Alternative embodiments comprise having the filter manufactured as an integral part of the container as depicted in FIG.  4 A, or having the filter incorporated into a self-contained removable filter unit or cartridge as depicted in FIG.  4 B. 
     A further alternative embodiment comprises a D-ring attached to the end of pin  50  connected to the cover  16 . In this embodiment, the filter and filter retainer are mounted on the inside of the sterilization container. This arrangement permits the external D-ring to be used as a handle to lift the cover without coming into contact with the side edges of the cover  16 , thereby reducing the risk of contamination of the container contents. 
     While the foregoing embodiment works sufficiently well in a flash sterilization environment, it has been found that improvements to the basic structure of the invention are desirable if used with gas plasma. Gas plasma as a sterilization medium is fairly new and is available from, among others, Advanced Sterilization Products, a division of Johnson &amp; Johnson, under the trademark STERRAD®. Gas plasma has certain advantages over the prior art. For example, ethylene oxide has been banned thereby making it more difficult to find suitable alternatives. In addition, steam sterilization cannot be used with a number of modem tools, such as cannulas, lumens, scopes, fiber optic cables, and cameras, without damaging them. While gas plasma clearly has certain distinct advantages, it has been found that it does not operate suitably well with all types of containers that were suitable for use with steam sterilization. Part of the problem is that the gas plasma does not circulate as aggressively as steam inside the container, and does not reach areas such as the corners, thereby leaving the potential for unsterilized surgical instruments or the like. Steam sterilization avoids the absorption problem by having a super-saturated environment of water molecules. The present invention, however, has provided a way for making gas plasma acceptable for use in sterilization containers, especially those in the mid-size range. For the purposes of this disclosure, mid-size is defined as approximately 15-18″ in length, 9-12″ in width and 2-10″ in depth. The present invention, especially in the mid-size container, has several advantages, including but not limited to, the following: 1) it cuts the exposure time in steam sterilization; 2) it improves the effectiveness of gas plasma sterilization; and 3) it is more efficacious for gravity displacement applications. 
     A first alternative embodiment  100  of the improved gas plasma sterilization container apparatus is illustrated in the exploded view of FIG.  5 A. The container  100  includes a top or lid  102  that sits on top of a bottom or pan  104 . Bottom  104  includes four sidewalls  106  and a bottom or base  108 . A pair of wire handles or bales  110  are located on opposite ends of the bottom portion  104  and are held in place by a pair of lockable latches  112 . 
     A first set of vent holes  114  is located in top  102 . The vent holes  114  are preferably arranged as a group of four concentric circles with holes  114   a ,  114   b ,  114   c  and  11   4   d  in each, respectively. In all, the total number of holes may range from 100 to 500 and have a size that ranges in diameter from, but not limited to, {fraction (3/16)}″ to {fraction (5/16)}″. The first set of vent holes  114  is located on the central axis  122  of the short dimension of the lid  102 . The first set of vent holes  114  allows the sterilizing medium  162  to pass into the container. A pull ring  130 , attached to a base  142  sits in the middle of the first set of vent holes  114  and is connected there by rivet assembly  144   a ,  144   b , and  144   c  as shown in exploded detail in FIG.  5 D. The lid  102  also includes four recessed dimples  136  which are adapted to engage With complimentary dimples or projections in the base  108  (not shown) so that the containers  100  can be stacked on each other and permit circulation of gas plasma therethrough at the same time. 
     A second set of vent holes  116  and a third set of vent holes  118  are located in the base  108  on symmetrical opposite sides of center line  120  which represents the minor axis of the base  108 . The second set of vent holes  116  also comprises four concentric circles having holes  116   a ,  116   b ,  116   c  and  116   d  of the same dimensions with regard to the first set of vent holes  114 . A hold-down stud  132  is located in the center of the concentric circles and is intended to make a snap fit with the retainer plate for the hydrophobic filter that goes therebetween. Similarly, the third set of vent holes  118  comprises four sets of concentric circles having holes  118   a ,  118   b ,  118   c  and  118   d  therein. A central post or stud  134  is also located in the middle thereof and adapted to snap into and engage a hydrophobic filter retainer plate in the manner previously described with regard to the flash sterilization embodiment. Associated with the first set of vent holes  114  is a circular hydrophobic filter disk  124 , a hold down ring  126  and a perforated filter retainer plate  128 . A central hole  156  in the retainer plate  128  snaps into and engages a stud  146  in the container as illustrated in FIG. 5E. A similar set of hydrophobic filters, rings, and retainer plates is associated with the second and third set of vent holes  116  and  118  as illustrated in FIG.  5 F. Hydrophobic filters  124  should be utilized when gas plasma acts as the sterilizing medium, whereas cellulosic filters can be used when steam or ethylene oxide acts as the sterilizing medium. The TYVEK®, a trademark of E.I. du Pont de Nemours &amp; Company, brand of polyethylene/polypropylene spun fiber is acceptable, as is Kimguard®, a trademark of the Kimberly-Clark Corporation. The alternative embodiments  100  and  200  also work best with hydrophobic filters such as described above. In addition, hydrophobic filters do not absorb water, which allows for a quicker drying time. The concentric holes  128   a ,  128   b ,  128   c ,  128   d  and  128   e , are preferably offset from the holes  114   a ,  114   b ,  114   c , and  114   d  so as to the prevent “strikethrough”. That is to prevent sharp objects from entering the holes  114   a ,  114   b ,  114   c  and  114   d  and exiting through  128   a ,  128   b ,  128   c ,  128   d  or  128   e . As illustrated in FIG. 5C the top or lid  102  includes a groove  138  which retains a gasket  140  which sits on top of the upper lip  150  of the bottom or base pan  104  as shown in FIG.  5 F. FIG. 5F also shows in further detail how the bottom perforated retainer plate  152  attaches to the bottom stud  132  and keeps a hydrophobic filter in place above the second set of vent holes  116 . Similarly, FIG. 5F also illustrates how another perforated filter retainer plate  154  engages snap on stud  134  to hold another hydrophobic filter in place above the third set of perforated vent holes  118 . 
     The structure just described works especially well with gravity displacement or gas plasma. The gas plasma enters through the vent holes  114 , passes through the hydrophobic filter  124  and emerges through the perforated base plate  128 . Because the top vent holes  114  are not located directly above the bottom pair of vent holes  116  and  118 , the gas plasma is forced to migrate and become somewhat turbulent as it attempts to find an exit through the second and third set of circular vent holes  116  and  118 , respectively. This forces the gas plasma to more thoroughly mix and contact medical instruments or the like inside of the container  100  and also forces it further towards the corners and edges of the container. As a consequence, the invention described is one of a few containers, if any, that has been approved by major manufacturers for use with gas plasma. It is believed that no sealed container in the mid-size range for sterilization of blades and cannulas has been approved at the present time. The present invention in the mid-size range with the offset sets of vent holes works in all methods of sterilization, including flash sterilization, steam sterilization, and gas plasma sterilization. 
     A second alternative embodiment  200  of the gas plasma version is illustrated in an exploded view shown in FIG.  6 A. The base, or bottom pan  104  of the embodiment  200  is identical in all respects to the base  104  illustrated in FIG.  5 A and associated with the first gas plasma alternative embodiment  100 . Namely, the base  104  also includes a pair of offset circular vent holes  116  and  118  each having a hydrophobic filter and a retainer plate associated therewith as seen, for example, in detail in FIG.  5 F. The difference between embodiment  100  and  200  is that alternative embodiment  200  includes a pair of circular sets of vent holes  202  and  204  arranged symmetrically on opposite sides of the small dimension center line  226 . The structure of the first and second set of vent holes  202  and  204  is identical to the structure of the set of vent holes  114  in the lid  102  of embodiment  100  as illustrated in FIGS. 5A-5F. Namely, the first set of vent holes  202  comprises four concentric circles of vent holes  202   a ,  202   b ,  202   c  and  202   d . A pull ring  218  connected to a base  220  is located in the center of the concentric circles  202 . Pull ring  218  is attached by a rivet assembly  244   a ,  244   b , and  244   c  as illustrated in exploded detail in FIG.  6 D. Similarly, the second set of vent holes  204  comprises four concentric circles having vent holes  204   a ,  204   b ,  204   c  and  204   d arranged around a pull ring  222  attached to a base  224  and connected to the lid  226  in the same manner as illustrated in FIG.  6 D. The first set of vent holes  202  has associated with it a hydrophobic filter disk  206 , a ring  208 , and a perforated retainer plate  210  that snaps and attaches to a post on the bottom side of the base plate  220  in the same manner that the post  146  of the embodiment  100  engages its perforated retainer plate  128  as illustrated in FIG.  5 E. Similarly, another hydrophobic filter disk  212  is located under the second set of vent holes  204 , and has an associated ring  214  and perforated retainer plate  216  below it which also engages with a snap on post associated with pull ring  222  and base plate  224 . This second alternative embodiment  200  also provides for improved circulation of the gas plasma through the container so as to contact all the surgical instruments and the corners of the device. 
     In summary, the two gas plasma alternative embodiments  100  and  200  make it possible to convert a flash sterilization container such as illustrated in FIGS. 1A through 4B into a version which is imminently acceptable and suitable for use with mid-size sterilization containers. Not only does it work with mid-size containers, it also permits sterilization to take place in approximately half the time and works especially well in a gravity displacement environment. Moreover, delicate instruments, such as cameras which cannot be sterilized with steam or ethylene oxide, can be effectively sterilized. 
     While the invention has been described with reference to the preferred embodiment, it will be appreciated by those of ordinary skill in the art that modifications can be made to the structure and form of the invention without departing from the spirit and scope thereof

Technology Classification (CPC): 8