Patent Publication Number: US-2011070124-A1

Title: Steam sterilization system for sterilizing medical waste

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a steam sterilization system for sterilization of items such as regulated medical waste, and more particularly concerns a steam sterilization system that integrates material handling with the sterilization process to reduce handling and pathogen exposure. 
     2. Description of the Prior Art 
     Regulated medical waste generated by hospitals and the like is required to be sterilized prior to being disposed. Typically, plastic and/or rubber carts of approximately one cubic yard in size are used in hospitals to collect medical waste which has been placed in waste containment systems (i.e., sharps containers, sealed red plastic bags, etc.). The plastic/rubber carts are used to collect and to haul the containment systems containing the medical waste to the hospital&#39;s sterilization unit, where the waste containment systems containing the medical waste are unloaded from the cart and placed into the sterilization unit to be sterilized. After sterilization, the waste containment systems containing the now sterilized medical waste are transferred back onto the cart and conveyed to typically a solid waste compactor unit for final disposal, generally, in a sanitary landfill. 
     Sterilization units that are based upon steam sterilization generally have a drawback of water condensation from the steam forming on the treated medical waste, which increases the weight of the treated medical waste and therefore the cost of the disposing of the treated medical waste in a landfill. 
     Sterilization units based upon a vacuum autoclave have the drawback of potentially pumping airborne pathogens out of the vacuum autoclave into the environment during a sterilization process. This leads to potential contamination or alternatively to higher costs in providing filtration systems/ventilators for treating the airborne pathogens being pumped out of the vacuum autoclave. 
     My U.S. Pat. No. 6,867,393, which is incorporated herein by reference, discloses a steam sterilization system for sterilizing medical waste and a method of sterilizing medical waste that uses the combination of steam and vacuum. The system comprises a cart for carrying a removable bin for holding medical waste, and a sterilization chamber that receives the bin when it is removed from the cart. The bin may be rolled from the cart and rolled into the chamber along respective rail assemblies on the cart and in the chamber, where the medical waste in the bin is sterilized, and upon completion of the sterilization process, the bin may be rolled from the chamber back onto the cart and transported by the cart to a dumping location. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a sterilization system for sterilizing items such as regulated medical waste. 
     Another object of the invention is to provide a sterilization system that avoids the condensation drawback of known steam based sterilization units as well as the airborne pathogen drawback of known vacuum autoclave systems. 
     Another object of the invention is to provide a sterilization system that provides the efficacy of a vacuum based sterilization system without the airborne pathogen drawback mentioned above. 
     Still another object of the invention is to provide a sterilization system that integrates material handling with the sterilization process, thereby reducing handling and pathogen exposure. 
     Another object of the invention is to refine and expand on the sterilization system and the sterilization method disclosed in my U.S. Pat. No. 6,867,393. 
     These and other objects are accomplished by my invention which is set out below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view in perspective of a sterilization system constructed in accordance with the invention, showing a removable bin for holding items (such as medical waste) to be sterilized just prior to being rolled from a cart which has been positioned before a sterilization chamber, into the sterilization chamber for commencement of a sterilization process to sterilize the items to be sterilized in accordance with the invention; 
         FIG. 2  is a view in side elevation of the system of  FIG. 1 , after the removable bin has been rolled into the sterilization chamber; 
         FIG. 3  is an end view of the system of  FIGS. 1 and 2 , illustrating the interior of the sterilization chamber; 
         FIG. 4  is a view in side elevation of the cart and the bin of  FIGS. 1-3 , with the latching assembly  61  disengaged from the front wheels  57   a  of the bin  15 ; 
         FIG. 5  is an enlarged view of wheel  57  of the bin  15  riding on the rail  44  of the cart rail assembly  43  shown in the circle  5  of  FIG. 4 ; 
         FIG. 6  is a view taken along the lines and arrows  6 - 6  of  FIG. 5 ; 
         FIG. 7  is a view in side elevation of the cart and the bin of  FIGS. 1-3 , with the hook arms  63  and  65  of the latching assembly  61  engaged around the front wheels  57   a  of the bin  15 ; 
         FIG. 8  is an enlarged view of the hook arms  63  and  65  of the latching assembly  61  engaging a front wheel  57   a  shown in the circle  8  of  FIG. 7 ; 
         FIG. 9  is an enlarged view of the latching assembly  73  and the rod  67  and actuator  69  of the latching assembly  61  shown in the circle  9  of  FIGS. 1 ,  18 , and  19 , except that the actuator  69  has been moved into a position placing the hook arms  63  and  65  into a disengaged (unlatched) position shown in  FIG. 4 ; 
         FIG. 10  is an enlarged view of the alignment mechanism shown in the circle  10  of  FIG. 1 ; 
         FIG. 11  is a view in partial cross-section taken along the lines and arrows  11 - 11  of  FIG. 18 ; 
         FIG. 12  is a view in side elevation showing the bin  15  being dumped; 
         FIG. 13  is a schematic drawing illustrating the steam, vacuum and water systems used in conjunction with the sterilization system of the invention; 
         FIG. 14  is a chart identifying the valves used in the system of the invention; 
         FIGS. 15   a ,  15   b , and  15   c  combined show a chart illustrating the three phase sterilization process of the invention with example settings; 
         FIG. 16  is chart providing illustrative parametric settings for various load weights of items to be sterilized; 
         FIG. 17  is a chart illustrating the wash cycle of the invention with example settings; 
         FIG. 18  is a view in perspective showing an alternative embodiment of the bin removably mounted on the cart; 
         FIG. 19  is a view in perspective showing another alternative embodiment of the bin removably mounted on the cart; 
         FIG. 20  is a chart illustrating the dry sterilization process of the invention with example settings; 
         FIG. 21  is a view in side elevation showing an alternative embodiment of the sterilization chamber, with a cutaway of the chamber wall to illustrate the interior of the chamber; 
         FIG. 22  is a view in elevation of a pole  141  used to pull a bin  15 ,  15 ′, or  15 ″ from the interior of the chamber  17 ′ shown in  FIG. 21 ; and 
         FIG. 23  is a chart identifying various variable timers that may be used in preferred embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Turning to the drawings, there is shown a steam sterilization system  11  for sterilizing medical waste. In this preferred embodiment of the invention, the steam sterilization system  11  comprises a cart  13 , a bin  15  for holding medical waste, the bin  15  being removably mountable to the cart  13 , and a sterilization chamber  17 . 
     As shown in drawings, and particularly in  FIGS. 1-4 ,  7 , and  12 , the cart  13  for carrying the removable bin  15  has a front end portion  19 , a rear end portion  21 , and two side end portions  23 ,  25 . The cart  13  has a rectangular-shaped base frame portion  27  having a pair of cross beams  29  and  31  extending between the side beams  33 ,  35 . The cart  13  also includes a handle support frame portion  37  extending upwardly from the base frame portion  27  at the rear end portion  21  of the cart  13 , and a handle assembly  39  is mounted onto the handle support frame portion  37  to facilitate pushing of the cart  13 . Preferably, the cart  13  is constructed of aluminum alloy to reduce weight, and is anodized to provide a corrosion resistant surface that is easily cleaned. 
     Wheels  41 , preferably the rear two being castor wheels and the front two being fixed wheels, are mounted on the underside of the base frame portion  27  of the cart  13  to provide mobility to the cart  13 . Preferably, the wheels  41  have a 5″ diameter and are made of polyethylene, so as to provide smooth handling over various surfaces and to not mark or damage finished flooring. 
     A floor brake  42  is mounted on the cross beam  31  of the frame portion  27  of the cart  13 , and, when in an engaged position reached by being activated by foot pressure applied by a cart user, engages the floor to hold the cart  13  in place when unattended, when positioned at the chamber opening  85  for unloading of the bin  15  from the cart  13  to the chamber  17  or loading of the bin  15  from the chamber  17  to the cart  13 , or when the bin  15  is to be dumped by tilting as described below after the items contained therein have been sterilized. 
     A rail assembly  43  is provided on each side beam  33 ,  35  of base frame portion  27  of the cart  13 , and each rail assembly  43  has a rail  44 . 
     As shown in the drawings, and particularly in  FIGS. 1-4 ,  7 , and  12 , the bin  15  in this preferred embodiment of the invention has a bottom wall  45 , and a front wall  47 , a rear wall  49 , and two side walls  51 ,  53  extending upwardly the bottom wall  45 . Preferably the bin  15  is fabricated from corrosion resistant stainless steel and has a 33⅞ inch width, a 59 inch length, and a height of about 36 inches, with an approximate usable volume of 1.25 cubic yards. The two side walls  51  and  53  of the bin  15  are angled in slightly from top to bottom, and the front wall  47  of the bin  15  is more dramatically angled in from top to bottom. A drain valve  55 , preferably a ½ inch ball valve, is connected to the bottom wall  45  near the rear wall  49  of the bin  15  for permitting liquid to drain from the bin  15  when desired. 
     The bin  15  is provided with wheels  57 , including front wheel  57   a,  mounted on each side wall  51 ,  53  of the bin  15 . The wheels  57  are spaced such that the wheels  57  engage the rail assemblies  43  located on the side end portions  23  and  25  of the cart  13  so that the bin  15  may be rolled off the cart  13  along the rails  44  when the bin  15  is being loaded into the sterilization chamber  17  from the cart  13  and so that the bin  15  may be rolled onto the cart  13  along the rails  44  and  90  when the bin  15  is being loaded onto the cart  13  from the sterilization chamber  17  after sterilization. 
     Handle grips  59  are mounted on the rear wall  49  and on the side walls  51 ,  53  of the bin  15  to facilitate handling of the bin  15 . 
     As shown in detail in  FIGS. 4 ,  7 ,  8  and  9 , a latching assembly  61  is provided on each side end portion of the cart  13  for latching the bin  15  to the cart  13 , when desired. Each latching assembly  61  includes a pair of hook arms  63 ,  65  pivotally mounted on the cart  13  for engaging the front wheel  57   a  on the side of the bin  15  that the latching assembly  61  is located to prevent the bin  15 , when it is positioned on the cart  13 , from moving forward on the rail assemblies  43  of the cart  13  when it is desired to have the bin  15  secured to cart  13 . A rod  67  is connected at one end to the hook arms  63  and  65 , and at the other end to an actuator  69 , which is used to move the rod  67  which thereby causes the hook arms  63  and  65  to pivot through a slot  71  formed in each rail assembly  43  into an engaged position around the wheel  57   a  or into a disengaged position shown in broken lines and double dots in  FIG. 8 . 
     As shown in the drawings, and particularly in  FIG. 9 , a pair of latching assemblies  73  also is provided. Each latching assembly  73  has a catch  75  mounted on a bracket  77  formed on the rear wall  49  of the bin  15 , and a latching member  79  mounted on a bracket  81  on the cart  13 . Latching apparatus  73  operates like a lunch box latching apparatus, with latching member  79  latching onto the catch  75  to prevent the bin  15  from rolling forward off the cart  13  and to prevent the rear end portion of the bin  15  from being lifted off the cart. The brackets  81  mounted on the cart  13  also act as a stop to prevent the bin  15  from rolling rearwardly on the rail assemblies  43  beyond the brackets  81 . 
     The sterilization chamber  17  has in interior  83  where sterilization takes place. The sterilization chamber  17  has an opening  85  through which access to the interior  83  of the sterilization chamber  17  is obtained, and the sterilization chamber  17  has a door  87  mounted at the opening  85  for sealingly closing the opening  85  against both pressure and vacuum when closed. The sterilization chamber  17  preferably is 60 inches in diameter and 64 inches long, and is constructed of corrosion resistant stainless steel. It is mounted on chamber support cradles and positioned at a convenient elevation for use in conjunction with the cart  13  and bin  15 . The chamber  17  is sloped slightly downwardly from front to back to facilitate drainage. As shown in  FIGS. 1 and 2 , the door  87  preferably is a full opening hinged door that provides unobstructed access to the sterilization chamber  17  when the door  87  is fully opened. The door  87  preferably is equipped with either an automatic or manual latching mechanism to seal the door against both pressure and vacuum. Also, the door  87  preferably is equipped with safety innerlocks to prevent operation of the chamber  17  when the door  87  is ajar and to prevent opening the door until safe pressure and temperature conditions are restored. 
     Preferably, the sterilization chamber  17  is equipped with a pressure relief valve device to prevent over pressurization, and preferably, the sterilization chamber  17  is designed and constructed in accordance with the ASME, Code Section VIII, Division 1, and may receive an ASME “U” stamp as an unfired pressure vessel. The chamber  17  preferably at least meets Seismic Zone 3 specifications. 
     As shown in  FIGS. 1 and 2 , the sterilization chamber  17  is provided with a rail assembly  89  that is located in the interior  83  of the sterilization chamber  17 . The rail assembly  89  has pair of parallelly spaced rails  90  on which the wheels  57  of the bin  15  ride when the bin  15  is inserted into the sterilization chamber  17  from the cart  13  prior to sterilization and on which the wheels  57  of the bin  15  ride when the bin  15  is being removed from the sterilization chamber  17  and rolled back onto the cart  13  via rail assemblies  43  after sterilization. Preferably, the rail assembly  89  is made of stainless steel. 
     To facilitate aligning the rails  44  of the rail assemblies  43  of the cart  13  with the rails  90  of the rail assembly  89  of the chamber  17 , the front ends of the rails  90  are angled and the front end of each rail  90  has a plate  91  mounted thereacross to form a surface against which a tapered stop  92  (preferably made of Teflon) mounted on the front end of each rail  44  may engage and ramp against to properly align the rails  44  with the rails  90  when the cart  13  is pushed forward toward the chamber  17 . 
     The chamber  17  is fitted with two thermal energy booster apparatuses  93  mounted opposite each other on each side of the interior  83  of the chamber  17  and extending the length of the chamber  17 . The thermal energy booster apparatuses  93  preferably are made of corrosion-resistant stainless steel and are designed to withstand the system pressures and temperatures. The thermal energy booster apparatuses  93  provide dry heat to the interior  83  of the chamber  17  to aid in the vaporization of fluids in the chamber  17  and provide a heat source for the dry heat sterilization process of the invention. Preferably, the thermal energy booster apparatuses  93  are plates, which I refer to as Thermal Energy Booster Plates, having a conduit  95  formed therein for carrying steam, such that the apparatuses  93  act like radiators to provide dry radiant heat to the interior  83  of the chamber  17 . 
     As shown in  FIGS. 2 and 3 , a water spraying assembly  97  is provided to the sterilization chamber  17  for cooling the bin  15  after sterilization and prior to removal of the bin  15  from the sterilization chamber  17 . The water spraying assembly  97  includes nozzles  99  mounted in the interior  83  of the sterilization chamber  17  that are aligned to spray cooling water on the outside of the side walls  51  and  53  of the bin  15 . The nozzles  99  spray water to cool down the bin  15  after sterilization has occurred and are arranged to do so by spraying the outside of the walls of the bin  15 . The nozzles  99  are arranged so as not to get water on the treated, sterilized waste held in the bin  15 . 
     The water spraying assembly  97  also is provided with nozzles  100 , which are used together with nozzles  99 , when it is desired to spray pressurized water onto the bin  15  (both the exterior and interior sides of the bin walls) to clean and rinse the bin  15 . Accordingly, the invention provides for periodic cleaning of the bin  15  in the chamber  17 , rather than requiring manual cleaning at a remote location. 
     A drain valve  101  is connected to the sterilization chamber  17  for liquid to drain from the sterilization chamber  17  when desired. 
     As shown schematically in  FIG. 13 , piping  103  is provided to supply steam, preferably at 15 to 20 psig, to the sterilization chamber  17 . A solenoid controlled steam valve  105  (Main Steam Valve MS- 1  as referred to in  FIGS. 13 ,  14 , and  15   a ,  15   b , and  15   c ) is provided along the piping  103  to control the flow of steam into the sterilization chamber  17 . Piping  107  branches off piping  103  to provide steam to the thermal energy booster apparatuses  93 , and a solenoid controlled steam valve  108  (Auxiliary Steam Valve AS- 2  as referred to in  FIGS. 13 ,  14 , and  15   a ,  15   b , and  15   c ) is provided along the piping  107  to control the flow of steam into the thermal energy booster apparatuses  93 . Preferably, a manual isolation valve  106 , preferably a manual ball valve, is provided along the piping  103  upstream from the solenoid steam control valves  105  and  108  as a safety feature. When the sterilization system  11  is not in use, the isolation valve  106  may be manually closed to prevent steam from accidentally flowing into the sterilization chamber  17  if the steam valve  105  opens and to prevent steam from accidentally flowing into the thermal energy booster apparatuses  93  if the steam valve  105  opens. 
     A vacuum pump  109  is provided for evacuating the sterilization chamber  17  between steam cycles during the sterilization process. The vacuum pump  109  is provided along piping  111 . Preferably, the vacuum pump  109  is a single stage, liquid ring pump that uses water as the seal fluid and that is suited as a vapor pump. The vacuum pump  109  preferably is connected to the sterilization chamber  17  through a stainless steel manifold and is isolated by a solenoid-activated vacuum valve  113  (Vacuum Pump Suction Valve VS- 6  as referred to in  FIGS. 13 ,  14 , and  15   a ,  15   b , and  15   c ) and a solenoid activated vacuum valve  114  (Vacuum Discharge Valve VD- 7  as referenced to in  FIGS. 13 ,  14 , and  15   a ,  15   b , and  15   c ). 
     Piping  103  includes a vent portion  115  for venting the sterilization chamber  17  to atmosphere, and a valve  117  (Main Vent Valve MV- 3  as referred to in  FIGS. 13 ,  14 , and  15   a ,  15   b , and  15   c ), preferably an electro-magnetic solenoid activated valve, is provided along piping vent portion  115  to open and close the vent portion  115 . 
     Piping  119  is provided to supply water, preferably at 30 psig minimum, to the vacuum pump  109  and to the water spraying assembly  97 . 
     A valve  121  (Vacuum Pump Water Seal Valve VWS- 15  as referred to in  FIGS. 13 ,  14 , and  15   a ,  15   b , and  15   c ), preferably an electro-magnetic solenoid valve, is provided along the piping  119  to allow the flow of water (to be used as seal fluid) to the vacuum pump  109 . Preferably, a manual flow valve  126  (Flow Control Valve VWS- 16  as referenced to in  FIGS. 13 ,  14 , and  15   a ,  15   b , and  15   c ) is provided upstream of the valve  121  to control the flow of water to the vacuum pump  109 . 
     A valve  122  (Water Spray Valve WS- 8  for cool-down of bin  15  as referred to in  FIGS. 13 ,  14 , and  15   a ,  15   b , and  15   c ), preferably an electro-magnetic solenoid activated valve, is provided along the piping  119  to allow the flow of water to the nozzles  99  of the water spraying assembly  97 . Preferably, a manual flow valve  124  (Flow Control Valve WSF- 10  as referenced to in  FIGS. 13 and 14 ) is provided upstream of the valve  122  to control the flow of water to the nozzles  99 . 
     A valve  123  (Water Spray Valve WS- 9  for washing bin  15  as referred to in  FIGS. 13 ,  14 , and  15   a ,  15   b , and  15   c ), preferably an electro-magnetic solenoid activated valve, is provided along the piping  119  to allow the flow of water to the nozzles  100  of the water spraying assembly  97 . Preferably, a manual flow valve  125  (Flow Control Valve WSF- 11  as referred to in  FIGS. 13 and 14 ) is provided upstream of the valve  123  to control the flow of water to the nozzles  100 . 
     An isolation valve  127 , preferably a manual ball valve, is provided along piping  119  upstream of the valve  121 , valve  122 , and the valve  123  as a safety feature to be manually closed when the sterilization system  11  is not in use. 
     Referring to  FIG. 2 , a programmable logic controller  131  is connected to the system  11  and manages sequential control functions and system interlocks. The controller  131  controls the steam valves  105  and  108 , vent valve  117 , the drain valve  101 , the vacuum valves  113  and  114 , the liquid ring and water supply valve  121 , the cooling spray valve  122 , the wash spray valve  123 , and the vacuum pump  109 , and it monitors and records process temperature and pressure. The controller  131  is preferably housed in a weather-proof NEMA enclosure. 
     The system  11  also includes a scale  135  for weighing the items to be sterilized. The weight of the items to be sterilized is inputted into the controller  131 , which varies the process times, process temperatures, and process pressures to predetermined settings that correlate to the weight of the items to be sterilized, thereby enabling the system  11  to sterilize varying levels of biological (germ) load, waste mass, and quantities of fluids. Preferably, the scale  135  is linked to the controller  131  such the weight of the items to be sterilized measured by the scale  135  is automatically transmitted to the controller  131 , which then varies the process times, process temperatures, and process pressure to predetermined settings that correlate to the weight measured by the scale  135 . The matrix that defines how the parametric variables are adjusted has been empirically established using beta-testing of the efficacy of the various process times, various process temperatures, and various process pressures. 
     A programmable logic controller  131  manages the sequential control, fault, diagnostic and system interlock functions. An onboard interconnected computer provides authorized access to settings, data logging for each cycle, periodic processing statistics and maintenance records. An onboard plain paper printer and data storage device prints a comprehensive single page report for each cycle including pressure and temperature charts and has the capacity to maintain all of the processing and maintenance records for a period of up to seven years. Ethernet capability makes it possible for authorized personnel to remotely view real time processing information, faults and diagnostic information as well as generate periodic processing reports right at their desk. The system is fully automated and features a multi-function operator interface. The interface provides simple cycle selection and start up for the operator. Optionally, the system may be programmed to require operator identification before any function can be activated or any fault condition can be acknowledged or reset. The operator may also view in real time the progress of the process along with the temperature and pressure or vacuum inside the chamber. 
     As shown in  FIG. 4 , a removable lid  139  is provided for covering the bin  15 . Preferably, the removable lid  139  is made of light-weight plastic and is hinged to provide easy access to the bin  15  without requiring removal of the entire lid  139  from the bin  15 . The entire lid  139  is removed prior to the bin  15  being rolled into the sterilization chamber  17  during the sterilization process. 
     In operation, the cart  13  having the bin  15  secured thereon is used to collect regulated medical waste to be sterilized. The regulated medical waste that is to be sterilized is placed in the bin  15 . The lid  139  is preferably used to cover the bin  15  and the medical waste contained therein during collection. The preferred hinged lid  139  shown in the drawings facilitates access to the bin  15  for placement of medical waste therein. 
     After the medical waste has been collected, the cart  13  with the bin  15  mounted thereon is moved to the sterilization chamber  17 , where the lid  139  is removed from the bin  15  and placed aside. Next, with the door  87  of the sterilization chamber  17  opened, the cart  13  is then pushed to the opening  85  of the sterilization chamber  17  so that the tapered stops  92  engage and ramp against the alignment plates  91  to assure that the cart  13  is properly aligned with the opening  85  of the sterilization chamber  17 , thereby aligning the rails  44  of the rail assemblies  43  of the cart  13  with the rails  90  of the rail assembly  89  of the sterilization chamber  17 . 
     When the cart  13  has been pushed up against the sterilization chamber  17  with the rails  44  properly aligned with the rails  90 , the floor brake  42  is engaged to hold the cart  13  in place. 
     Then, preferably, the cart  13 , with the bin  15  attached thereto and containing the items to be sterilized, is weighed on scale  135  and the weight measured by the scale  135  is transmitted to the controller  131 , which determines the weight of the items to be sterilized by subtracting the known weight of the cart  13  and bin  15  from the gross weight measured by the scale  135 , and adjusts the process times, the process temperatures, and the process pressures as needed to predetermined settings that correlate to the calculated weight of the items to be sterilized. 
     Next, the latching members  79  are unlatched from catches  75 , and the hook arms  63  and  65  are disengaged from the front wheels  57   a,  to permit the bin  15  to roll forward on the rails  44 . The bin  15  is then rolled on its wheels  57  along the rail  44  from the cart  13  into the interior  83  of the sterilization chamber  17  along the aligned rails  90 . 
     Once the bin  15  has been rolled into the sterilization chamber  17 , the floor brake  42  is disengaged and the cart  13  is rolled away from the sterilization chamber  17 . 
     Then, the drain valve  55  of the bin  15  is opened and the door  87  of the sterilization chamber  17  is closed. 
     The start button on the controller  131  is then pressed to start the sterilization process. First, the controller  131  opens the steam valve  108  (Auxiliary Steam Valve AS- 2 ) to feed steam to the thermal energy booster apparatuses  93  to provide dry radiant heat from the thermal energy booster apparatuses  93  to the interior  83  of the chamber  17 . Then, the controller  131  opens the steam valve  105  to permit steam to fill the sterilization chamber  17 . The controller  131  closes the vent valve  117  and the drain valve  101  of the sterilization chamber  17  when the sterilization chamber  17  is full of steam. Prior to the closing of the vent valve  117  and the drain valve  101 , the air in the sterilization chamber  17  outside the waste container systems (i.e., sharps containers, sealed red plastic bags, etc.) is “gravity” displaced by the steam being fed into the sterilization chamber  17 . 
     A thermocouple is mounted in the interior  83  of the sterilization chamber  17  and is connected to the controller  131  to indicate the temperature inside the interior  83  of the sterilization chamber  17 . After 250° Fahrenheit is reach within the interior  83  of the sterilization chamber  17 , the controller  131  initiates a hold period to kill all airborne pathogens in the containment systems. Preferably, the hold period is about 5 minutes, but can be adjusted to various time lengths based on the pathogen load factor. 
     Next, the controller  131  closes the steam valve  105  and then cycles open the vent valve  117  until the pressure in the sterilization chamber  17  goes to zero gauge pressure. The controller  131  then opens drain valve  101  to drain sterile condensate, and the controller  131  then closes the drain valve  101 . Next the controller  131  opens valves  121 ,  113  and  114  and initiates the vacuum pump  109  to draw a vacuum in the sterilization chamber  17  to remove the now sterilized air from the containment systems. 
     After creating a vacuum withdrawing the air from within the containment systems, the controller  131  stops the vacuum pump  109  and closes the associated valves  113 ,  114  and  121 . The controller  131  then opens steam valve  105  admitting high temperature, high pressure steam commencing the waste sterilization cycle. After a preferred retention period of 45 minutes at or above 250° Fahrenheit (or longer if required by the location, state&#39;s regulations etc.), the controller  131  closes steam valve  105 , and the controller  131  again cycles open the vent valve  117  until the pressure in the sterilization chamber  17  goes to zero gauge pressure. The controller  131  then opens drain valve  101  to drain sterile condensate, and the controller  131  then closes the drain valve  101 . 
     Next, with the thermal energy booster apparatuses  93  continuing to provide heat to aid in the vaporization of fluids in the chamber  17 , the controller  131  opens the valves  113 ,  114  and  121  and initiates the vacuum pump  109  to draw a vacuum to vaporize the condensate and fluids remaining in the chamber  17 . After the waste is dry, the controller  131  shuts off the vacuum pump  109 , closes the valves  113 ,  114  and  121 , and closes the steam valve  108  (Auxiliary Steam Valve AS- 2 ). The controller  131  then opens the air inlet valve  153  (Air Inlet Valve AI- 4  as referred to in  FIGS. 13 ,  14 , and  15   a ,  15   b , and  15   c ) to break the vacuum in the chamber  17 . When the chamber  17  reaches 0 psig, the controller  131  then opens the valves  117  and  101 . 
     At this point, to cool the cart, the controller  131  opens the valve  122  to let cooling water flow to and through the water nozzles  99  of the water spraying assembly  97  to spray cooling water on the outside of the walls  51  and  53  of the bin  15  to cool down the bin  15 . Upon the bin  15  having been cooled, the controller  131  closes the valve  122 . At this point, the controller  131  signals, preferably by initiating a green light located on the enclosure for the controller  131 , that the door  87  may be opened and the bin  15  removed from the sterilization chamber  17 . 
     The door  87  is then opened, the drain valve  55  of the bin  15  is closed, and the cart  13  is again located adjacent to the opening  85  of the sterilization chamber  17  with the tapered stops  92  at the front ends of the rails  44  ramped into contact with the plates  91  at the front ends of the rails  90 , thereby aligning the rails  44  of the rail assemblies  43  of the cart  13  with the rails  90  of the rail assembly  89  of the sterilization chamber  17 , and with the cart  13  held in place by engaging the floor brake  42  again. 
     With the cart  13  thus positioned, the bin  15  containing the sterilized items may be rolled from the interior  83  of the sterilization chamber  17  onto the cart  13  along the rail assemblies  43  and  89 . After the bin  15  has been fully rolled onto the cart  13 , it may then be locked in place on the cart  13  by latching the latching members  79  onto the catches  75  and by engaging the hook arms  63  and  65  around front wheels  57   a,  thereby securing the bin  15  onto the cart  13 . 
     With the bin  15  secured on the cart  13 , the floor brake  42  may be released, thereby permitting the cart  13  to be pulled away from the sterilization chamber  17 . 
     The cart  13  with the bin  15  mounted thereon may be moved to a dump location where the sterilized waste may be dumped into a compactor or other suitable container. 
     Now, the items that have been sterilized may be dumped from the bin  15  at the dump location. Preferably, the floor brake  42  is first re-applied to hold the cart  13  in position. Next, while maintaining the hook arms  63  and  65  of each latching assembly  61  around the front wheels  57   a,  the latching members  79  are released from the catches  75  to disengage the rear end portion of the bin  15  from the cart  13  to permit the bin  15  to be pivoted around the front wheels  57   a  to enable the bin  15  to be tilted forward by lifting the rear end portion of the bin  15  to lower the front end of the bin  15 . The rear end portion of the bin  15  is then lifted, preferably using handle grips  59 , to tilt the bin  15  forward so the sterilized items slide down the front wall  47  of the bin  15  and out of the bin  15 . 
     Alternatively, the latching members  79  may remain latched onto the catches  75  to secure the rear end portion of the bin  15  on the cart  13 , and the cart  13  with the bin  15  secured thereon may be dumped as a cart/bin unit using existing dumping apparatus. 
     The lid  139  may now be replaced onto the bin  15 . The cart  13  with the bin  15  mounted thereon is now ready to be used to gather more medical waste for sterilization. 
     For exemplary purposes, the inventive method described above is illustrated in  FIGS. 15   a ,  15   b , and  15   c.    
     When it is desired to wash the bin  15 , the bin  15  is placed inside the chamber  17  and the chamber door  87  is closed. The controller  131  closes valve  153  (Air Inlet Valve AI- 4 ) and opens valve  108  (Ancillary Steam Valve AS- 2 ). The controller  131  then opens drain valve  101  (Drain Valve D- 5 ), opens valve  123  (Water Spray Valve WS- 9 ) and valve  122  (Waterspray Valve WS- 8 ) to spray pressurized water onto the bin  15  from nozzles  99  and  100  to wash the bin  15 . Then, the controller  131  closes valves  123  and  122  and permits the water in the chamber  17  to drain from the chamber  17 . Next, the controller  131  closes valve  101 , closes valve  108 , and opens valve  153 . After the pressure in the chamber  17  reaches 0 psig and the bin has cooled, the bin  15  is removed from the chamber  17 . For exemplary purposes, the washing process is illustrated in  FIG. 17 . 
     Turning now to  FIG. 18 , there is shown an alternative embodiment of the invention in which bin  15 ′ is substituted for bin  15 . In this embodiment, the remaining components of system  11  described above remain the same. 
     Bin  15 ′ in this preferred embodiment of the invention is substantially identical to bin  15 , except for its shape, load capacity, and the number of wheels  57  mounted thereon. Bin  15 ′ is substantially box-shaped and has a bottom wall  45 ′, a front wall  47 ′, a rear wall  49 ′, and two side walls  51 ′,  53 ′ extending upwardly from the bottom wall  45 ′. Preferably, the bin  15 ′ is fabricated from corrosion resistant stainless steel and has a 33⅞ inch width, a 59 inch length, and a height of about 36 inches, with an approximate usable volume of 1.5 cubic yards. The two side walls  51 ′ and  53 ′ of the bin  15  are angled in slightly from top to bottom. 
     A drain valve  55 , preferably a ½ inch ball valve, is connected to the bottom wall  45 ′ near the rear wall  49 ′ of the bin  15 ′ for permitting liquid to drain from the bin  15 ′ when desired. 
     The bin  15 ′ is provided with wheels  57 , including middle wheels  57   b,  mounted on each side wall  51 ′,  53 ′ of the bin  15 ′. The hook arms  63  and  65  of the latching assemblies  61  engage the middle wheels  57   b  when the bin  15 ′ is secured on the cart  13 . The wheels  57  are spaced such that the wheels  57  engage the rail assemblies  43  located on the side end portions  23  and  25  of the cart  13  so that the bin  15 ′ may be rolled off the cart  13  along the rails  44  when the bin  15 ′ is being loaded into the sterilization chamber  17  from the cart  13  and so that the bin  15 ′ may be rolled onto the cart  13  along the rails  44  and  90  when the bin  15 ′ is being loaded onto the cart  13  from the sterilization chamber  17  after sterilization. 
     Handle grips  59  are mounted on the rear wall  49 ′ and on the side walls  51 ′,  53 ′ of the bin  15  to facilitate handling of the bin  15 . 
     Like bin  15 , bin  15 ′ is provided with a pair of catches  75  mounted on brackets  77  formed on the rear wall  49 ′ of the bin  15 ′, and these catches  75  interact with latching members  79  mounted on the cart  13  as part of the latching assembly  73  to latch bin  15 ′ onto cart  13  when desired. 
     In use, bin  15 ′ is used in the same manner as the bin  15 , except the bin  15 ′ is dumped using existing dumping apparatus, where the cart  13  with the bin  15 ′ secured thereon by the latching assemblies  61  and  73  is dumped as a cart/bin unit. 
     Turning now to  FIG. 19 , there is shown another alternative embodiment of the invention in which a bin  15 ″ is substituted for bin  15 . In this embodiment, the remaining components of system  11  described above remain the same. 
     Bin  15 ″ in this preferred embodiment of the invention has a bottom wall  45 ″, a front wall  47 ″, a rear wall  49 ″, and two side walls  51 ″,  53 ″ extending upwardly from the bottom wall  45 ″. Bin  15 ″ is substantially identical to bin  15 , except for its shape and load capacity, and except that bin  15 ″ does not have a drain valve  55  or handle grips  59  on its rear wall  49 ″. Preferably, the bin  15 ″ is fabricated from corrosion resistant stainless steel and has a 33⅞ inch width, a 59 inch length, with an approximate usable bottom wall surface of about 13.8 square feet. 
     The bin  15 ″ is provided with wheels  57 , including middle wheels  57   b,  mounted on each side wall  51 ″,  53 ″ of the bin  15 ″. The hook arms  63  and  65  of the latching assemblies  61  engage the middle wheels  57   b  when the bin  15 ″ is secured on the cart  13 . The wheels  57  are spaced such that the wheels  57  engage the rail assemblies  43  located on the side end portions  23  and  25  of the cart  13  so that the bin  15 ″ may be rolled off the cart  13  along the rails  44  when the bin  15 ″ is being loaded into the sterilization chamber  17  from the cart  13  and so that the bin  15 ″ may be rolled onto the cart  13  along the rails  44  and  90  when the bin  15 ″ is being loaded onto the cart  13  from the sterilization chamber  17  after sterilization. 
     Handle grips  59  are mounted on the side walls  51 ″,  53 ″ of the bin  15 ″ to facilitate handling of the bin  15 ″. 
     Like bin  15 , bin  15 ″ is provided with a pair of catches  75  mounted on brackets  77  formed on the rear wall  49 ″ of the bin  15 ″, and these catches  75  interact with latching members  79  mounted on the cart  13  as part of the latching assembly  73  to latch bin  15 ″ onto cart  13  when desired. 
     In use, bin  15 ″ is used in the same manner as the bin  15 , except that bin  15 ″ is used in a dry sterilization process of the invention, and the bin  15 ″ is manually unloaded rather than dumped after the sterilization process since the items to be sterilized, such as documents and things, are not destroyed. 
     Specifically, the paper and/or things to be sterilized is/are collected in the bin  15 ″ that is removably mounted on the cart  13 , and the paper and/or things to be sterilized is/are transported using the cart  13  with the bin  15 ″ removably mounted thereon to the sterilization chamber  17 . The cart  13  is positioned at the sterilization chamber  17  such that the rails  44  of the cart  13  at the front end portion of the cart  13  abut against and are in alignment with the rails  90  of the sterilization chamber  17 . Preferably the paper and/or things to be sterilized is/are then weighed on the scale  135 . With the floor brake  42  engaged, the bin  15 ″ is disconnected from the cart  13  and rolled on its wheels  57  from the cart  13  into the sterilization chamber  17  along the aligned rails  44  and  90 . Preferably, the controller  131  is used to recognize the weight of the items to be sterilized measured by the scale  135  and to vary process times and process temperatures to predetermine settings that correlate to the weight measured by the scale  135 . The sterilization chamber  17  is heated with dry radiant heat generated from the thermal energy booster apparatuses  93  to an effective temperature to sterilize the paper and/or things in the bin and maintain the temperature at or above the effective temperature until sterilization of the paper and/or things has been accomplished. After sterilization has been accomplished, the bin  15 ″ and its contents are allowed to cool. The bin  15 ″ is then removed from the chamber  17  by rolling the bin  15 ″ along the rails  90  from the chamber  17  onto the rails  44  of the cart  13 . The bin  15 ″ is re-secured on the cart  13  using latching assemblies  61  and  73 , the floor brake  42  is released, and the cart  13  with the bin  15 ″ secured thereto containing the sterilized items therein is moved to where it is desired to unload the sterilized items. The floor brake  42  is then re-applied and the sterilized items are unloaded from the bin  15 ″. 
     For exemplary purposes, the inventive method described above is illustrated in  FIG. 20 . 
     Turning now to  FIG. 21 , there is shown another embodiment of the invention in which the chamber  17 ′ is substituted for the chamber  17 . 
     Chamber  17 ′ in this preferred embodiment is identical to chamber  17 , except that chamber  17 ′ is a double capacity chamber, that is, a chamber having sufficient length to accommodate two bins end to end. The chamber  17 ′ has substantially the same design and construction specifications as chamber  17 , except that the rail assembly  89 ′ has a longer length than the rail assembly  89  to accommodate two bins end to end, the water spraying assembly  97 ′ has a longer length than the water spraying assembly  97  to accommodate the length of two bins, and four thermal energy booster apparatuses  93  are mounted in chamber  17 ′ (two on each side of the chamber  17 ′) rather than the two that are mounted in the chamber  17 . 
     Any of bins  15 ,  15 ′ or  15 ″ may be used in chamber  17 ′ or chamber  17 . However, chamber  17 ′ may accommodate two bins at once. Each bin  15 ,  15 ′, and  15 ″ is provided with a handle  139  on its rear wall  49 ,  49 ′,  49 ″ to facilitate removal of the bins  15 ,  15 ′, or  15 ″ from the chamber  17 ′, especially the innermost bin  15 ,  15 ′, or  15 ″ in the chamber  17 ′ when two bins are used. 
     Using a pole  141  having a hook  143  formed at one end portion ( FIG. 22 ), the bin  15 ,  15 ′, or  15 ″ may be pulled from the chamber  17 ′ by inserting the pole  143  into the chamber  17 ′, hooking the hook  143  onto the handle  139 , and then pulling on the pole  141  to pull the bin  15 ,  15 ′, or  15 ″ from the chamber  17 ′ along the rails  90 ′ of rail assembly  89 ′. 
     As is detailed above, the inventive sterilization process in a preferred embodiment uses a combination of steam injection and vacuum to treat potential airborne pathogens, to enhance heat transfer, and to increase system efficacy. The use of vacuum removes residual air and provides and transport mechanism for steam delivery. Sterilization is accomplished using steam at a pressure of 15 psig, which corresponds to an operating temperature of 250° Fahrenheit. 
     An important characteristic of my inventive sterilization system  11  is management of airborne pathogens. In a preferred embodiment, the sterilization process cycle begins by gravity charging the sterilization chamber  17  with steam, thereby increasing the temperature to the killing temperature for airborne pathogens, then subsequently removing the air from the waste containment systems (i.e., sharps containers, sealed red plastic bags, etc.) which kills airborne pathogens that might otherwise be released through the discharge of the vacuum pump  109 . 
     The sterilization system  11  is preferably used with medical waste containment systems having ventilation means formed therein. Venting the containment systems allows steam to permeate confined volumes of the containment systems and accelerates the heating cycle. 
     The use of vacuum in combination with dry heat in a preferred embodiment of my invention promotes the vaporization of fluids and the removal of the resultant vapors. 
     My sterilization system  11  provides a material handling system that accommodates the complete cycle of the processing medical waste, including the collection of medical waste, sterilization of the medical waste, and the transportation and dumping of the treated medical waste from the sterilization unit to the treated sterilized waste facility compactor. The handling system eliminates the need to transfer waste products from a collection cart to the sterilizer, thereby improving pathogen containment. Further, the handling system eliminates the need to transfer treated sterilized waste product from the sterilizer to the plastic/rubber carts for transportation to the hospital&#39;s compactor. 
     The material handling system provided by my invention reduces physical handling of the waste material by hospital personnel thereby reducing the chances of injury to hospital personnel since the waste material need not be physically handled by hospital personnel after it is initially loaded into the bin  15 . 
     The material handling system provided by my invention also provides for sterilization of items, such as paper documents and other things, that are not to be discarded after sterilization.