Patent Publication Number: US-2023148051-A1

Title: System and method for vaporized hydrogen peroxide cleaning of an incubation chamber

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to, as a continuation application, the non-provisional application filed May 19, 2020, assigned application Ser. No. 16/877,826, titled “System and Method for Vaporized Hydrogen Peroxide Cleaning of An Incubation Chamber” (attorney docket no. 12560-006CON) and further claims priority to assigned application Ser. No. 15/382,915, titled “System and Method for Vaporized Hydrogen Peroxide Cleaning of An Incubation Chamber” (attorney docket no. 12560-006) filed Dec. 19, 2016 and further claims priority to the provisional application filed on Dec. 18, 2015 and the entire contents of which are hereby incorporated by reference as if fully set forth herein, under 35 U.S.C. § 119(e). 
    
    
     BACKGROUND OF THE INVENTION 
     Mammalian cell culturing in an incubation chamber is typically conducted at simulated human body conditions of 37 C (98.6 F) and moist environments (humidity 90%, just below dew point where condensation occurs). While mammalian cells grow best at these conditions, so does bacterial cells, mold and other unwanted organisms. These menaces can contaminate and ruin cell culture studies. For this reason, periodic decontamination and/or sterilization cycles are performed on cell culture equipment. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       A preferred embodiment of the invention, illustrated of the best mode in which Applicant contemplates applying the principles, is set forth in the following description and is shown in the drawings and is particularly and distinctly pointed out and set forth in the appended claims. 
         FIG.  1    is a front elevational view of a first embodiment of the insulated chamber of the present invention with portions shown diagrammatically. 
         FIG.  2    is a sectional view taken on Line  2 - 2  of  FIG.  1   . 
         FIG.  3    is a sectional view taken on Line  3 - 3  of  FIG.  2   . 
         FIG.  4    is a sectional view taken on Line  4 - 4  of  FIG.  2   . 
         FIG.  5    is similar to  FIG.  2    and is a sectional view of a second embodiment of the chamber of the present invention. 
         FIG.  6    is a perspective view with portions cut away of the removable and repositionable phase change material packet or wall of the present invention. 
         FIG.  7    is a sectional view similar to  FIG.  2    of a third embodiment of the chamber of the present invention utilizing the phase change material packets. 
         FIG.  8    is a sectional view similar to  FIG.  7    of a fourth embodiment of the present invention also utilizing the phase change packets. 
         FIG.  9    is a sectional view similar to  FIG.  2    of a fifth embodiment of the chamber of the present invention utilizing a heating element between the insulation and phase change material. 
         FIG.  10    is a sectional view similar to  FIG.  9    of a sixth embodiment of the chamber of the present invention utilizing a heating element between the phase change material and the inner layer of the skin. 
         FIG.  11    is a sectional view similar to  FIG.  5    of a seventh embodiment of the chamber of the present invention wherein the phase change material is contained within numerous encapsulated pellets which are within a liquid medium. 
         FIG.  12    is a sectional view of one of the encapsulated pellets. 
         FIG.  13    is a sectional view similar to  FIG.  12    of an eighth embodiment of the chamber of the present invention showing the phase change material within encapsulated pellets which are embedded in a solid matrix. 
         FIG.  14    is a perspective view of a PCM packet or shelf having recesses formed therein for receiving respective storage items. 
         FIG.  14 A  is a sectional view taken on line  14 A- 14 A of  FIG.  14   . 
         FIG.  15    is a sectional view similar to  FIG.  7    of a ninth embodiment of the chamber of the present invention using the PCM packets or shelves shown in  FIG.  14   . 
         FIG.  16    is a sectional view similar to  FIG.  15    with the door removed and portions cut away to illustrate the use of the PCM packets or shelves inside and outside of the chamber. 
         FIG.  17    is a flow chart illustrating various methods of the present invention. 
         FIG.  18    is a graph that shows temperature and humidity levels during a conventional H202 cleaning cycle of an incubator. 
         FIG.  19    is a front elevational view of an embodiment of a system for vaporized hydrogen peroxide cleaning of an incubation chamber. 
         FIGS.  20 A- 20 B  are front perspective views of one embodiment of a module for vaporized hydrogen peroxide cleaning of an incubation chamber. 
         FIGS.  21 A- 21 B  are rear perspective views of the embodiment of the module of  FIGS.  20 A- 20 B . 
         FIGS.  22 A- 22 B  are perspective views of one embodiment of a catalyst and fan positioned within the module of  FIGS.  21 A- 21 B . 
         FIG.  23    is a partial block diagram of the embodiment of the system of  FIG.  19   . 
         FIG.  24    is a flowchart depicting one embodiment of a method for operating the system of  FIG.  19    during a vaporized hydrogen peroxide cleaning of the incubation chamber. 
         FIG.  25    is a flowchart depicting one embodiment of a method for vaporized hydrogen peroxide cleaning of an incubation chamber. 
         FIG.  26    is a graph that shows one embodiment of temperature and humidity levels during a H202 cleaning cycle using the system of  FIG.  19   . 
         FIG.  27    is a graph that shows one embodiment of temperature and humidity levels during a H202 cleaning cycle using the system of  FIG.  19   . 
         FIG.  28    is a graph that shows one embodiment of temperature and humidity levels during a H202 cleaning cycle using the system of  FIG.  19   . 
     
    
    
     Similar numbers refer to similar parts throughout the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     There are several well-established and effective methods of contamination control in an incubation chamber for use in cell culturing. They include: 
     Manually wiping the chamber with a cleaning agent such as H2O2 
     Introducing moist air at 90 C into the chamber 
     Introducing dry air at 140 C into the chamber 
     Introducing dry air at 180 C into the chamber 
     Employing a HEPA (high efficiency particulate air) filter 
     Introducing UV (ultraviolet) germicidal light into the chamber 
     Introducing chloride dioxide gas into the chamber 
     Using formalin/paraformaldehyde 
     Introducing vaporized hydrogen peroxide (H2O2) (wet) into the chamber 
     Introducing vaporized hydrogen peroxide (H2O2) (dry) into the chamber 
     The use of H2O2 vaporized hydrogen peroxide is one of the fastest methods (taking minutes instead of hours) and the market is gravitating in that direction. 
     One prior art H2O2 cleaning cycle utilizes a ‘wet’ H2O2 cycle that is cumbersome to use, expensive, labor intensive, and simply not practical. As a result, this cleaning cycle has not been well received by users. 
     A conventional H2O2 cycle comprises four basic steps. This list of steps below does not include the preparatory and post-cleaning work in setting up the equipment and then removing it when cleaning is complete. 
     1. Dehumidify the chamber air to increase its moisture-absorption capacity by: 
     A. Dehumidifying using mechanical refrigeration (like a household dehumidifier); or 
     B. Raising the temperature of the chamber air since the capacity of air to retain moisture increases as the temperature increases. 
     2. Condition the air with H2O2 according to: A. A dry cycle conditioning technique by increasing the relative humidity to about 90% and injecting H2O2 during this process. This 90% value represents about the maximum amount of moisture the air can hold without risking condensation; or 
     B. A wet cycle conditioning cycle technique by fogging the air with H2O2 solution until its saturation point is reached. Condensation will occur when using this approach. 
     Generally, during a dry cycle, as the name implies, there is no condensation within the chamber. If the user touches the interior walls they will feel ‘dry’. Condensation occurs during a wet cycle and the chamber interior surfaces become damp with H2O2. At the end of a ‘wet’ cycle, H2O2 (or H2O once the H2O2 has been decomposed) will be pooled up on the chamber floor in a puddle. 
     3. Sterilize the chamber by holding the H2O2 conditions for a specified time needed to ‘kill’ the unwanted cells, i.e., about three to fifteen minutes at 37 C and longer at lower temperatures 
     4. Inactivate the H2O2. 
     While the H2O2 kills unwanted cells, it is also harmful to good cells. A very low level of H2O2 (as measured in ppm) must be reached (during the inactivation step) before the chamber air is safe for human exposure. Any one or a combination of several different techniques can be employed to remove/decompose the H2O2 into water (H2O) and oxygen (O2). 
     A. Wait a period of time. H2O2 is naturally unstable and decomposes over time 
     B. Accelerate the process by elevating the air temperature 
     C. Accelerate the process by using UV light 
     D. Accelerate the process by using a catalyst such as silver 
     Another prior art decontamination cycle is described below and illustrated in a graph  300  in  FIG.  18   . Horizontal axis  360  is time in units of minutes. Left vertical axis  362  is temperature in units of Celsius (C). Right vertical axis  364  is relative humidity in percentage (%). 
     1. Dehumidify the chamber by increasing an air temperature  320  over a first time period  312  from an initial temperature  326  to an interior temperature of 37 C (Method  1 B from ‘basic four steps’). This causes the relative humidity  322  to drop from an initial humidity  328  (e.g. 60% rh) to 30% rh. That means the air can handle an additional amount of moisture equivalent to the amount of humidity  322  removed (additional 30%=60%-30%). The total amount of moisture that the air can absorb is now 60% (=90%-30%). 90% is the total amount of moisture that air can handle and avoid condensation. (99% is the theoretical value, but this is not practical in an incubator.) 30% relative humidity is the amount of water in the air at the end of the dehumidification phase. The difference between these two values is 60% and represents the additional amount of moisture that can be added to the air. This step takes the first time period  312 , which is about ten minutes. 
     2. Inject H2O2 (H2O2) of some concentration (e.g. 35%) such that a combined humidity  324  of H20 and H202 reaches 90% rh. The combined humidity  324  at about 90% is a combination of H2O (water) and H2O2 (hydrogen peroxide) vapor. The humidity  322  indicates only H2O vapor at 65% (30% was already in the air plus when injecting the H2O2 additional water vapor is injected into the air). The difference between the combined humidity  324  and humidity  322  (e.g. 25%) then is the amount of H2O2 in the air. This conditioning step takes a second time period  314 , which is about five minutes. 
     3. Hold the temperature  320  and combined humidity  324  (e.g. H2O2 levels) constant during the sterilization step over a third time period  316 , which is about twelve minutes duration. 
     4. At the beginning of the H2O2 inactivate step turn on a fan that blows air through a silver catalyst (Method  4 D from ‘basic four steps’). The catalyst converts the H2O2 to harmless H2O and O2. As the combined humidity level  324  approaches the humidity  322  (at about 46 minutes of elapsed time) the amount of H2O2 approaches 0 and it is then safe for human exposure. The temperature  320  stays at 37 C as elevated temperature accelerates the reaction too. This step takes a fourth time period  318 , that lasts about twenty minutes. 
     A first embodiment of the insulated enclosure or chamber of the present invention is shown generally at  1  in  FIG.  1   , with additional embodiments shown generally at  1 A in  FIG.  5   , at  1 B in  FIG.  7   , at  1 C in  FIG.  8   , at  1 D in  FIG.  9   , at  1 E in  FIG.  10   , at  1 F in  FIG.  11   , at  1 G in  FIG.  13   , and at  1 H in  FIG.  15   . Chamber  1  is configured to serve as an incubator, environmental chamber, oven, refrigerator or freezer. Chamber  1  includes a main body or container  3 , a storage interior chamber  4  defined by container  3 , a door  5  and a control assembly  7  secured to and seated atop container  3 . Container  3  in the exemplary embodiment is in the form of a five-sided or five-walled box-like structure wherein the forward terminal ends of four of these walls define an entrance opening  6  ( FIG.  2   ) of interior chamber  4 . Upper and lower horizontal shelves  2  are disposed within interior chamber  4  extending between three of the walls of container  3  and suitably supported therein for supporting thereon one or more storage items  40  (dashed lines) to be stored in interior chamber  4  over a duration typically measured in hours, days, or weeks. Storage item  40  may, for example, be one or more petri dishes or other containers for growing cultures or for supporting other items which need incubation or heating in a controlled manner. Storage item  40  may also include the contents of a dish or container, such as a culture, and may include other components, some of which are discussed in greater detail further below. Item  40  may also be cooled in a controlled manner and frozen if desired. Insulated chamber is configured to heat and/or cool item  40  and/or to maintain item  40  within interior chamber  4  at a desired temperature, as described further below. Door  5  is hingedly attached to container  3  by hinges  9  to swing between open ( FIG.  1   ) and closed ( FIGS.  2 ,  4   ) positions. An annular sealing gasket  11  provides a seal between door  5  and container  3  when door  5  is closed, such that main body  3  and door  5  together form a six-sided or six-walled container or enclosure. Items  40  are removable from and insertable into (Arrows A in  FIGS.  2 ,  5     7 - 11  and  13 ) interior chamber  4  through entrance opening  6  when door  5  is open. 
     Door  5  includes a transparent window  12  which may be double paned ( FIG.  2   ) with two parallel panes  16  (typically made of glass) with an annular elastomeric seal  18  therebetween and in contact therewith to separate panes  16  by a space  20 . Space  20  is defined by the inner perimeter of seal  18  and panes  16  and is filled with gas or under vacuum to help thermally insulate interior chamber  4  when door  5  is closed to cover entrance opening  6 . Door  5  includes a rectangular annular wall  10  which surrounds window  12  along its outer edges and is hollow and typically includes a metal skin which defines a rectangular annular insulated fully enclosed door interior chamber or compartment  13  with thermal insulation  14  therein which nearly or completely fills compartment  13 . 
     Control assembly  7  includes an enclosure or housing  8  on which is mounted a manual control interface  15  and which houses a temperature control unit  17 , a humidity control unit  19  and a carbon dioxide control unit  21 . Interface  15  is in electrical communication with control units  17 ,  19  and  21 , and also with a fan assembly  23  within or in communication with interior chamber  4  and an electric power source  25  outside housing  8 . Temperature control unit  17  is in electrical communication with a temperature sensor  27  within or bounding interior chamber  4  and with an electric heating unit or device in the form of a heating coil  29  within interior chamber  4 . Temperature control unit  17  is also in electrical communication with a cooling device or refrigeration assembly  28  which includes internal heat-exchanging pipes  30  and external components  32  which typically include external heat-exchanging pipes, a compressor, and an expansion valve such that the refrigeration assembly provides a typical refrigeration cycle whereby the refrigerant within the coils is capable of providing active cooling within interior chamber  4  via the internal coils  30  therein. Cooling and heating devices  28  and  29  serve as electrically powered temperature-altering devices for altering the temperature of interior chamber  4 , items  40  and other components within chamber  4  and portions of the walls defining chamber  4 . Humidity control unit  19  is in electrical communication with a humidity sensor  31  within or bounding interior chamber  4  and with an actuator such as a solenoid of a water control valve  33  which is in fluid communication with a water source  35 . Thus, humidity control unit  19  is operatively connected to interior chamber  4  to control the amount of humidity within chamber  4 . Carbon dioxide control unit  21  is in electrical communication with a carbon dioxide sensor  37  and an actuator such as a solenoid of a carbon dioxide control valve  39  which is in fluid communication with a carbon dioxide source  41 . Thus, carbon dioxide control unit  21  is operatively connected to interior chamber  4  to control the level of carbon dioxide within chamber  4 . 
     Main body or container  3  is now described in greater detail. Container  3  has several generally rigid walls or sidewalls including a flat vertical rectangular back wall  42 , flat rectangular horizontal top and bottom walls  44  and  46  secured respectively to the top and bottom of back wall  42  and extending forward therefrom, and flat vertical left and right side walls  48  and  50  secured respectively to the left and right sides of back wall  42  and extending forward therefrom. Left and right side walls  48  and  50  are also secured to and extend between the respective left and right ends of top and bottom walls  44  and  46 . Walls  42 - 50  thus form a box or cup-shaped configuration defining interior chamber  4  such that walls  44 - 50  at their front ends define entrance opening  6 . A fully enclosed sealed rectangular cup-shaped interior cavity or chamber  52  is formed within container  3  separate from interior chamber  4  and more particularly is defined by a substantially rigid skin  54  which is typically formed of metal although it may be formed of a plastic or other suitable material. Chamber  52  surrounds interior chamber  4  on five sides thereof. Wall or sidewall chamber  52  is sealed from external atmosphere and is nearly or completely filled by insulation  56  and a phase change material  58  (PCM), each of which is also in a substantially rectangular cup-shaped configuration corresponding to that of chamber  52 . The phase change material  58  is disposed between the insulation and interior chamber  4  along the entire inner surface of insulation  56  and thus essentially completely surrounds interior chamber  4  on all five sides of container  3 . Thus, each of walls  42 - 50  includes several layers or materials. Insulation  56  may be formed of a variety of insulation materials which remain in a solid state throughout the operation of the chamber and which are generally rigid or compressible. For example, insulation  56  may be fiberglass, styrofoam, or various types of foam boards or sheets, such as those formed from polystyrene, polyurethane, polyisocyanurate and the like. Some of these insulation boards are referred to commonly as polyiso boards. PCM  58  is discussed in greater detail further below. Although PCM  58  is shown on all five sides of container  3  entirely surrounding interior chamber  4 , chamber  1  may also be formed with PCM  58  on only one, two, three or four sides of container  3  so that PCM  58  is adjacent chamber  4 , but does not surround chamber  4 . 
     Skin  54  includes a rectangular cup-shaped outer layer  60 , a rectangular cup-shaped inner layer  62  and a rectangular annular front layer  64  which is substantially vertical and extends between the front of outer and inner layers  60  and  62 . Outer layer  60  thus forms outer layers of each of the walls of container  3 , namely vertical rear outer layer  66 A of back wall  42 , horizontal top outer layer  66 B of top wall  44 , horizontal bottom outer layer  66 C of bottom wall  46 , vertical left outer layer  66 D of left side wall  48  and vertical right outer layer  66 E of right side wall  50 . Inner layer  62  similarly forms the inner layers of each of these walls, namely vertical front inner layer  68 A of back wall  42 , horizontal bottom inner layer  68 B of top wall  44 , horizontal top inner layer  68 C of bottom wall  46 , vertical right inner layer  68 D of left side wall  48  and vertical left inner layer  68 E of right side wall  50 . Each of layers  66  and  68  is flat and rectangular. 
     Insulation  56  likewise makes up insulation layers of each of the five walls of container  3  which abut the respective outer layer  66  thereof and extend inwardly therefrom part of the way toward the respective inner layer  68  thereof. More particularly, insulation  56  includes a vertical flat rectangular insulation layer  70 A of back wall  42  which abuts the front inner surface of outer layer  66 A and extends forward therefrom, a flat rectangular horizontal insulation layer  70 B of top wall  44  which abuts the lower inner surface of outer layer  66 D and extends downwardly therefrom, a flat rectangular horizontal insulation layer  70 C of bottom wall  46  which abuts the top inner surface of outer layer  66 C and extends upwardly therefrom, a flat rectangular vertical insulation layer  70 D of left side wall  48  which abuts the inner surface of outer layer  66 D and extends inwardly to the right therefrom, and a flat rectangular vertical insulation layer  70 E of right side wall  50  which abuts the left inner surface of outer layer  66 E and extends inwardly to the left therefrom. 
     PCM  58  also forms respective PCM layers of each of the walls of container  3 , namely a vertical flat rectangular PCM layer  72 A of back wall  42  which extends between and is in contact with the front inner surface of insulation layer  70 A and the rear surface of skin inner layer  68 A, a flat rectangular horizontal PCM layer  72 B which extends between and is in contact with the bottom inner surface of insulation layer  70 B and the top surface of inner layer  68 B, a flat rectangular horizontal PCM layer  72 C which extends between and is in contact with the upper surface of insulation layer  70 C and the lower surface of inner layer  68 C, a vertical flat rectangular PCM layer  72 D which extends between and is in contact with the inner surface of insulation layer  70 D and the left surface of inner layer  68 D, and a flat rectangular vertical PCM layer  72 E which extends between and is in contact with the left inner surface of insulation layer  70 E and the right surface of inner layer  68 E. Each PCM layer  72  is thus disposed within a cavity or portion of interior chamber  52  between the corresponding inner layer of the skin and layer of insulation  70 . 
     Chamber  1 A ( FIG.  5   ) is similar to chamber  1  except that it includes a door  5 A which is somewhat different than door  5  although both doors are substantially rigid and serve as a wall or sidewall of the chamber  1  or  1 A. Unlike door  5 , door  5 A does not include a transparent window which allows someone to view the contents of interior chamber  4  from outside the chamber without opening the door. Instead, door  5 A is opaque and has a configuration similar to one of the walls of container  3  and is thus made of several layers. In particular, door  5 A includes a substantially rigid skin  74  which is relatively thin and typically formed of metal and defines a fully enclosed vertical rectangular interior cavity or chamber  76  which is separate from chambers  4  and  52 , which is sealed from external atmosphere and in which are disposed an insulation layer  70 F and a PCM layer  72 F. Skin  74  includes outer and inner vertical rectangular layers  78  and  80  and a rectangular annular perimeter layer  82  which extends between and is secured to the respective outer perimeters of outer and inner layers  78  and  80  such that layers  78 - 82  define therewithin chamber  76 . Insulation layer  70 F extends from the top to the bottom and from the left side to the right side of interior chamber  76 . Insulation layer  70 F also abuts the inner surface of outer layer  78  and extends inwardly and rearwardly therefrom and may contact the front inner surface of inner layer  80  along its outer perimeter although insulation layer  70 F only extends part of the way towards inner layer  80  along a rectangular portion of door  5 A which is directly in front of entrance opening  6 . PCM layer  72 F is a flat vertical rectangular layer which extends between and abuts the front surface of inner layer  80  and the rear surface of insulation layer  70 F such that when door  5 A is closed, PCM layer  72 F entirely covers or spans the entrance opening  6  of interior chamber  4 . PCM layer  72 F is thus disposed within a cavity or portion of the sidewall or door interior chamber  76  defined between inner layer  80  and insulation layer  70 F. PCM layer  72 F is intended to be permanently disposed within chamber  76  and is thus not removable therefrom, just as the PCM layers  72 A-E are not removable from interior chamber  52  of container  3 . 
       FIG.  6    illustrates a removable PCM packet  84  which is typically easily carried by one person and otherwise manipulated with one or two hands for use with chambers configured to receive packet  84 . Packet  84  includes first and second substantially flat rectangular walls  86  and  88  which together form an outer skin and overlay one another such that their outer perimeters are superimposed and in contact with one another while the vast majority of walls  86  and  88  are spaced from one another to define therebetween a flat rectangular interior cavity or chamber  89  which receives therein a flat rectangular PCM layer  72 G which nearly or completely fills chamber  89 . Walls  86  and  88  are preferably formed of a substantially rigid thermally conductive material, such as a metal. Aluminum, stainless steel and copper are well suited for this purpose. However, walls  86  and  88  may be formed of a plastic or other suitable material. Packet  84  has first and second opposed straight parallel end edges  90  and  92 , and first and second straight parallel opposed side edges  94  and  96  which extend respectively between end edges  90  and  92  so that edges  90 - 96  form a rectangular configuration along the outer perimeters of walls  86  and  88 . Walls  86  and  88  are sealed to one another along each of edges  90 - 96  so that interior chamber  89  is fully enclosed and sealed from external atmosphere. 
     Chamber  1 B is shown in  FIG.  7    and utilizes removable PCM packets  84 . Chamber  1 B is similar to chambers  1  and  1 A and is shown with door  5  although a door such as door  5 A may also be used. Chamber  1 B includes a container  3 A which is similar to container  3  except that the insulation entirely or nearly entirely fills the interior chamber  52  since the PCM material is provided in packets  84  instead of within interior chamber  52 . Thus, for example, the insulation layer  70 A in the back wall of container  3 A extends all the way from the front surface of outer layer  66 A to the back surface of inner layer  68 A. Similarly, insulation layer  70 B extends continuously from the bottom surface of outer layer  66 B to the top surface inner layer  68 B, and insulation layer  70 C extends all the way from the bottom surface of inner layer  68 C to the top surface of outer layer  66 C. The insulation layers in the two side walls of container  3 A also extend all the way between the respective inner and outer layers thereof. 
     As shown in  FIG.  7   , the heating element  29  of chamber  1 B is mounted on the top wall of container  3  within interior chamber  4  adjacent the top thereof.  FIG.  7    further illustrates three of the removable PCM packets  84  within interior chamber  4 . One of packets  84  is seated on top inner layer  68 C of the bottom wall of container  3 , which thus serves as a supporting structure or permanent shelf for the lower packet  84 . Chamber  1 B further includes a pair of horizontal trays  98  which respectively hang downwardly from the wire or other type shelves  2  such that each tray and the respective shelf are adjacent one another and define therebetween a respective rectangular flat horizontal packet-receiving space  100  for removably inserting therein a respective packet  84  through a front entrance opening of a respective space  100 . Thus, the lowermost packet  84  is directly below the other two packets as well as directly below the two shelves and trays, and spaced downwardly from the lower tray. The middle packet  84  is thus seated atop the lower tray  98  below and adjacent the lower removable shelf  2 . Similarly, the top or upper packet  84  is seated atop the upper tray  98  below and adjacent the removable upper shelf  2 . In addition, the upper tray  98  is spaced upwardly from the lower shelf  2  so that a portion of interior chamber  4  is defined between the top of the lower shelf  2  and the bottom of tray  98  inasmuch as the upper tray  98  and the corresponding upper packet  84  is spaced upwardly from the lower shelf  2 . This portion of interior chamber  4  receives petri dishes or other items  40  which are seated on the lower shelf  2  so that the temperature of item  40  and the environment in interior chamber  4  surrounding item  40  may be controlled. Items  40  are thus adjacent, above and out of contact with the respective packet  84  during the process of temperature and other environmental control in interior chamber  4 . Similarly, interior chamber  4  includes an upper portion above the upper shelf  2  also configured to receive items  40 , which are likewise adjacent, above and out of contact with the upper packet  84  during the process of thermal and other environmental control within interior chamber  4 . As previously noted, each packet  84  may be inserted and removed from its respective space  100  or from atop the bottom wall (Arrows B in  FIGS.  7 ,  8   ) through the entrance opening  6  when door  5  is open. Trays  98  serve as PCM packet shelves. However, PCM packets  84  may also be seated on shelves  2  or another support so that items  40  may be seated directly on packets  84 . 
     Chamber  1 C ( FIG.  8   ) is similar to the previous chambers and includes a container  3 B which is similar to but somewhat modified from the earlier containers. The insulation within interior chamber  52  of container  3 B is the same as that described with reference to the insulation within container  3 A of chamber  1 B. As shown in  FIG.  8   , the heating element  29  is mounted adjacent and above the bottom wall of the container within interior chamber  4  in the same manner as with chamber  1 . Chamber  1 C illustrates the use of two PCM packets  84  in a different orientation than that shown with chamber  1 B. A tray  98  is mounted on the top wall of container  3 B within the upper portion of interior chamber  4  so that the upper PCM packet may slide horizontally (Arrow B in  FIG.  8   ) to be inserted or removed from the space  100  above tray  98  and below and adjacent the top wall of container  3 B. The other packet  84  is positioned in a vertical orientation behind removable shelves  2  abutting or adjacent the front inner surface of inner layer  68 A of the back wall of container  3 B. More particularly, a clip  102  is secured to the back wall adjacent the top wall of the container and clips or clamps the first end edge  90 , which serves as the top of packet  84  in the vertical orientation in order to suspend packet  84  in this rearward position. As will be appreciated, any suitable mechanism may be used in order to secure packet  84  in its hanging position or a vertical position closely adjacent the back insulating wall. PCM packets  84  of insulated chamber  1 B and  1 C are positioned so that they do not hinder the insertion and removal of items  40  from interior chamber  4 , that is, items  40  may be inserted and removed without moving PCM packets from their respective positions within chamber  4 . In addition, packets  84  are configured so that PCM  72 G (like the non-removable PCM  72  of chamber  1 ) is not visible to the end user of the insulated chambers  1 B and  1 C. Moreover, PCM packets  84  are configured and positioned in chamber  4  so that the space normally reserved for items  40  on shelves  2  (i.e., without the use of packets  84  or trays  98 ) is not substantially reduced, and in most cases the reduction in available space for items  40  is not significant enough to have any real impact. Thus, the items  40  normally placed in a chamber  4  of a given size may still be placed therein with the addition of trays  98  and/or packet(s)  84 . Although not shown, it is contemplated that a packet  84  may be positioned in a space behind or adjacent a “false” wall within chamber  4  such that the packet is hidden and whereby heat transfer to and from the packet is largely by convection. For example, such a false wall may be situated in front of the vertical packet  84  shown in  FIG.  8   . 
     Chamber  1 D ( FIG.  9   ) is similar to the previous chambers and includes a modified container  3 C such that the interior chamber  52  contains insulation, PCM, and a heating element  29 A sandwiched therebetween. The insulation layer  70 C of chamber  1 D is substantially the same as that described with regard to the chambers  1 B and  1 C in  FIGS.  7  and  8   . Similarly, the insulation in the left and right side walls of container  3 C completely or nearly fills the portions of chamber  52  within the respective left and right side walls of container  3 C. The insulation layers  70 A and  70 B of container  3 C are substantially the same as those of chamber  1 , as illustrated in  FIGS.  2  and  3   . In addition, the PCM layers  72 A and  72 B within container  3 C are substantially the same as that shown and described with reference to  FIGS.  2  and  3    of chamber  1 . In chamber  1 D, only these two PCM layers  72 A and  72 B are used such that the bottom wall and left and right side walls of container  1 D do not include such PCM layers. As  FIG.  9    illustrates, interior chamber  4  is free of a heating element such as heating element  29  of the previous embodiments. Instead, heating element  29 A is sandwiched between insulation layer  70 A and PCM layer  72 A and is thus substantially vertically oriented and in contact with each of said layers. Element  29 A is thus entirely external to interior chamber  4 . 
     Chamber  1 E ( FIG.  10   ) is similar to chamber  1 D except that it includes a heating element  29 A which is sandwiched between PCM layer  72 A and inner layer  68 A. Element  29 A is thus in contact with the rear surface of layer  68 A and the front surface of PCM layer  72 A. 
     Chamber  1 F ( FIG.  11   ) is similar to chamber  1 A ( FIG.  5   ) except that the various layers  72  of PCM  58  are replaced by numerous encapsulated PCM pellets  104  and a liquid medium  105  in which the pellets  104  are disposed. As shown in  FIG.  12   , each pellet  104  includes a solid capsule  106  having an inner surface which defines an interior chamber  108  or an enclosure which is sealed from the external atmosphere or environment by the solid skin or capsule  106 . Interior chamber  108  is nearly or completely filled with PCM  58 . As shown in  FIG.  11   , the mixture of pellets  104  and medium  105  form layers  110  which include a substantial amount of PCM  58  and are analogous to layers  72 . While layers  110  may be on all sides of interior chamber  4 ,  FIG.  11    shows only layers  110 A,  110 B,  110 C and  110 F, which are respectively analogous to layers  72 A,  72 B,  72 C and  72 F. Typically, pellets  104  are packed in as tightly or nearly as tightly as they can within the portion of interior chamber  52  defined between insulation  56  and inner layer  62  of skin  54 . Pellets  104  are similarly packed into the portion of interior chamber  76  of the door between the insulation layer  70 F and inner layer  80  of skin  74 . Pellets  104  define therebetween interstitial spaces which are typically completely or nearly filled by liquid medium  105 . Although in the exemplary embodiment, medium  105  is in a liquid form, it may also be in a gaseous form. In any case, the interior chamber  52  is completely or nearly filled by insulation  56 , pellets  104  and medium  105 . Similarly, the interior chamber  76  of the door is nearly or completely filled with insulation  70 F, pellets  104  and medium  105 . 
     As shown in dashed lines in  FIG.  11   , chamber  1 F may include an inlet  112  and an outlet  114  communicating with the portion of interior chamber defined between insulation  56  and inner layer  62  of skin  54  such that a liquid or a mixture of pellets  104  and liquid medium  105  may be pumped or otherwise moved into this portion of the interior cavity via inlet  112  (arrow C) and out of this portion of the interior cavity through outlet  114  (arrow D). The provision of an inlet and an outlet is one manner of filling this portion of the interior chamber  52  with pellets  104  and medium  105 , and also would allow for the pellets and medium to be removed via outlet  114  and, if desired, replaced with another set of pellets and liquid medium in which the PCM  58  of the pellets has a different melting or freezing temperature than that of the original pellets. It is noted that liquid  105  may be a phase change material which serves in the same fashion as PCM  58 , or it may remain in a liquid state within the operational parameters of chamber  1 F. The illustration with the use of inlet  112  and outlet  114  may represent the type of insulated chamber which uses a water jacket. Thus, instead of using the water jacketed insulated chamber in the standard manner, pellets  104  and liquid medium  105  may instead be used to fill the interior chamber of the water jacket in order to utilize the advantage of PCM  58  of the present invention. 
     Chamber  1 G ( FIG.  13   ) is similar to chamber  1 F in that it also utilizes PCM pellets  104 . However, instead of pellets  104  being disposed within liquid medium  105 , pellets  104  of chamber  1 G are embedded in a solid matrix  116 . More particularly, the matrix  116  and embedded pellets  104  form respective flat rectangular layers  118  which are analogous to PCM layers  72 A-F and layers  110  such that each of the layers is flat and rectangular and either horizontal or vertical as previously discussed with respect to layers  72 .  FIG.  13    shows specifically layers  118 A-C,  118 E and  118 F. However, unlike layers  72  and layers  110 , layers  118  are in the exemplary embodiment not within the interior chamber  52  defined by skin  54  of such chambers as chamber  1 ,  1 A and  1 F. Although layers  118  could be positioned within chamber  52  in the analogous positions of layers  72  and  110 , the use of layers  118  illustrates one manner of forming layers comprising PCM  58  wherein the layers are external to interior chambers  52  and  76 . Thus, chamber  1 G may include a container  3 D and a door  5 C each of which has a somewhat different configuration than those of the previous embodiments. Container  3 D retains skin  54  and its various layers to define there within the interior chamber  52 . However, insulation  56  itself either completely or nearly fills interior chamber  52 .  FIG.  13    shows that inner layers  68  of skin  54  are positioned closer to the corresponding outer layers  68  such that outer layers  66  abut the outer surface of insulation  56  and the inner layer  68  abut the inner surface of insulation  56 . Thus, insulation  56  in  FIG.  13    appears to have the same thickness as insulation  56  in  FIG.  11   . However, the inner and outer layers  66  and  68  may also be spaced apart from one another as in the previous embodiments such that insulation  56  still fills the entire chamber  52  and is thicker, as shown in  FIG.  7   . 
     Each of layers  118  has an outer surface  120  and an inner surface  122 . Each outer surface  120  of a given layer  118  which is part of container  3 D abuts an inner surface of a corresponding inner layer  68  so that each layer  118  extends inwardly therefrom to inner surface  122 . Thus, for instance, outer surface  120  of layer  118 A is vertical and abuts the vertical inner surface of back inner layer  68 A and extends inwardly therefrom to vertical surface  122  of layer  118 A. The outer surface  120  of layer  118 B serves as a top surface which thus abuts the inner or bottom surface of top inner layer  68 B so that layer  118 B extends downwardly therefrom to the horizontal inner or bottom surface  122  thereof. The outer surface  120  of layer  118 C thus serves as a bottom horizontal surface from which layer  118 C extends upwardly to the inner or top horizontal surface  122  thereof. The left and right walls of container  3 D are formed in a similar manner to the back wall thereof such that the corresponding layer  118  is vertical, and the inner and outer surfaces  120  and  122  of the corresponding vertical layers  118  (layer  118 E shown in  FIG.  13   ) are vertical and oriented such that the outer layer  120  abuts the corresponding inner layer  68  and extends inwardly therefrom to the vertical inner surface  122 . Thus, the inner surfaces  122  of the layers  118  define interior chamber  4 , unlike the earlier embodiments in which the inner layers  68  of skin  54  defined interior chamber  4 . 
     Although door  5 C is similar to the doors of the earlier embodiments, it also differs somewhat in that inner layer  80  defines a vertical flat rectangular recess  124  in which layer  118 F is received with its vertical outer or front surface  120  abutting the vertical inner surface of layer  80  and extending forward therefrom to the flat vertical inner or rear surface  122 , which bounds interior chamber  4  when door  5 C is closed. Although layer  118 F is shown disposed in recess  124 , a layer similar to  118 F may be mounted on a door without such a recess and thus project forward beyond the forward most portion of the inner skin. 
     In the exemplary embodiment, solid matrix  116  is typically formed of a cured resin. Thus, during formation of layers  118 , the original material which ultimately becomes matrix  116  is a liquid resin or in liquid form and thus cures to form the solid resin. In one embodiment, pellets  104  are mixed into a paint, which can then be painted onto any given surface, such as the inner layer  62  and the inner layer  80  and then allowed to dry. Paints typically contain a resin and a solvent, such that when the solvent dries, the resin is allowed to cure by chemical reaction. Some paints are also thermosetting, meaning that they are also heated in order to cure the resin. In another embodiment of solid matrix  116 , the resin may not include a solvent which needs to dry in order to cure. For example, some resins are simply heat cured from a liquid state to a solid state without or with extremely minimal evaporation of components making up the liquid resin. Other liquid resins may be light cured in order to reach the solid state. 
     Thus, the layers  118  may be formed in several different ways. Where the matrix and its liquid form is a paint, the paint with pellets  104  mixed into it may simply be painted onto a given desired surface and allowed to dry. Another option is to pour a given liquid resin with the pellets  104  mixed therein into a cavity or recess such as recess  124  (such as when door  5 C is laid horizontal with the recess  124  facing upwardly), and either allowed to dry, as with the paint, or cured by heat, light or any other suitable method in order to cure the resin within the recess. Alternately, any of the layers  118  may be independently formed in a mold cavity and subsequently mounted in the positions shown in  FIG.  13    by any suitable mechanism. For instance, the bottom layer  118 C may simply be laid atop the inner layer  68 C, or may be adhered with a glue or another adhesive thereto. The other layers  118  may similarly be adhered by a glue or an adhesive or so forth. Further, the various layers  118  of container  3 D may be formed as a single cup-shaped piece. Such formations may be done in a separate mold, or may use the inner layer  62  of skin  54  to define a portion of the mold. Matrix  116  may have varying degrees of thermal conductivity. The thermal conductivity may be enhanced by incorporating metal chips or other materials which are highly thermally conductive into the liquid resin during formation of the layers  118 . 
       FIG.  14    shows another PCM packet or shelf  84 A which is similar to packet  84  shown in  FIG.  6   . Shelf  84 A thus includes generally flat rectangular bottom wall  88  and a generally flat rectangular top wall  86 A which define therebetween an interior chamber  89 A which is filled with a layer  72 H of PCM. PCM layer  72 H typically completely or nearly fills interior chamber  89 A. It is noted that PCM layer  72 H of packet  84 A or PCM layer  72 G of packet  84  ( FIG.  6   ) may be replaced with pellets  104 , along with a gas or liquid medium  105  ( FIG.  11   ) or embedded in solid matrix  116  ( FIG.  13   ). Walls  86 A and  88  are formed of the same materials as previously described with regard to packet  84 , and are joined to one another to form end edges  90  and  92 , and side edges  94  and  96 . Unlike wall  86  of packet  84 , which is substantially flat in a continuous manner from adjacent edge  90  to adjacent edge  92  and from adjacent edge  94  to adjacent edge  96 , wall  86 A includes an upper flat portion  126  which extends from adjacent edge  90  to adjacent edge  92  and from adjacent edge  94  to adjacent edge  96 , but is interrupted by a plurality of recesses  128  extending downwardly therefrom. In the exemplary embodiment, packet  84 A includes six recesses  128  although the number may vary depending on the size of the packet and the specific need. Although recesses  128  may be of any desired shape, each recess  128  is shown with a circular central portion  130  and a pair of opposed finger receiving portions  132  which extend laterally outwardly from central portion  130  on opposite sides thereof and away from one another. The bottom of each recess  128  is defined by a flat horizontal recessed wall  134  which is spaced downwardly from upper flat portion  126 . An annular side wall  136  at its lower end is rigidly secured to and extends upwardly from the outer perimeter of recessed wall  134  to a rigid connection at its upper end to upper flat portion  126 , whereby each recessed wall  134  and the corresponding side wall  136  defines the corresponding recess  128 . Each recess  128  has a top entrance opening  138  through which a given storage item  40  may be downwardly inserted and upwardly removed, as indicated at arrow E in  FIG.  14   . 
     With continued reference to  FIG.  14   , the specific storage item  40  includes a container or petri dish  140  having a flat circular bottom wall  142  and a circular annular side wall  144  rigidly secured to and extending upwardly from the bottom wall  142  to define there within a cylindrical cavity  146  with a top entrance opening  148 . Cavity  146  is thus configured to receive various contents via entrance opening  148  and/or have the contents removed thereby. In the exemplary embodiment, item  40  includes the contents, which are in the form of a culturing medium  150  with living cells  152  to be grown or cultured thereon. 
     The sectional view of  FIG.  14 A  illustrates the relative positions of the petri dish  140  and its contents to the corresponding recess  128  and various components of the packet  84 A, including the PCM. The PCM of layer  72 H includes a lateral portion or portions  149  which may also be referred to as a recess-surrounding portion. The PCM of layer  72 H also includes respective sub-recess portions  151  which are located directly below the corresponding recess  128  and recessed wall  134 . The lateral portions  149  extend laterally outwardly from annular side wall  136  in all directions so that this portion of the PCM, as viewed from above, surrounds the corresponding annular side wall  136 , as well as the bottom wall  134 , recess  128 , and when petri dish  140  is disposed within  128 , also the bottom wall  142  thereof, at least a portion of side wall  144 , and all or part of medium  150  and cells  152 . Portions  149  have a top surface which abuts the bottom surface of upper flat portion  126  whereby the PCM of layer  72 H extends from below recessed wall  134  and the bottom of petri dish  140  to above recessed wall  134 , bottom wall  142 , most or all of side wall  144  and all or part of medium  150  and cells  152 . In the exemplary embodiment, bottom wall  142  of dish  140  is seated on horizontal flat recessed wall  134  with annular side wall  144  abutting or closely adjacent annular side wall  136 , which typically has a substantially similar shape as side wall  144  as viewed from above so that the petri dish side wall and the contents of the dish are adjacent portions  149  of PCM. In the exemplary embodiment, the top of the petri dish is no higher than the top of the top of upper flat portion  126  although this may vary. Likewise, the medium  150  and cells  152  are typically no higher than the top of portion  126 . 
     Referring now to  FIG.  15   , chamber  1 H is configured to use the packets or shelves  84 A shown in  FIG.  14   . Chamber  1 H is similar to chamber  1 B shown in  FIG.  7    except that chamber  1 H shows a different shelving configuration.  FIG.  15    illustrates that the lower packet or shelf  84 A is removably positioned atop inner layer  68 C of the bottom wall, similar to the lower packet  84  in  FIG.  7   . However, the middle packet or shelf  84 A is seated atop a wire or other shelf  2  rather than on a tray  98  as in  FIG.  7   . The bottom walls  88  of each of the lower and middle shelves or packets  84 A are atop a supporting surface or shelf whereby each packet  84 A serves as a shelf on which the various items  40  are seated within interior chamber  4 . The upper shelf  84 A of chamber  1 H is supported within interior chamber  4  in a different manner. More particularly, support ledges  154  are connected to and extend inwardly from the left and right walls defining interior chamber  4  in order to support the upper packet  84 A respectively along its left and right side edges  94  and  96 .  FIG.  15    shows only one of support ledges  154 , which extends from adjacent the back of interior chamber  4  to adjacent the front of interior chamber  4 . Thus, packet  84 A along the left and right edges  94  and  96  form respective lips which are seated on the support ledges  154 . These lips or side edges of packet  84  easily slide along support ledges  154  to insert the packet or shelf  84 A into chamber  4  or remove it therefrom via entrance opening  6  when door  5  is opened. 
     Although each of the chambers described above vary somewhat from one another, all of them operate in essentially the same basic manner. Various processes of the present invention are illustrated in the flow chart of  FIG.  17    at blocks  160 - 168  and will be referred to hereafter although not necessarily in the same order. Each insulated chamber is configured to control various atmospheric conditions within interior chamber  4  (block  162 ). For example, power source  25  provides the power for running the various electrical components of chamber  1 , such as fan assembly  23 , control units  17 ,  19 , and  21 , refrigeration assembly  28 , heating unit  29  and the solenoid or other actuator of control valves  33  and  39 . The user of chamber  1  manipulates the settings of temperature, humidity and CO 2  level within interior chamber  4  via control interface  15 , which may include three or more buttons or controls as shown in  FIG.  1    which correspond respectively to these three features. Sensors  27 ,  31  and  37  respectively sense or determine the temperature, humidity and CO 2  level within interior chamber  4  and produce respective signals which are sent respectively to temperature control unit  17 , humidity control unit  19  and CO 2  control unit  21 . Based on the signal from temperature sensor  27 , temperature control unit  17  controls heating unit  29  to turn it off, turn it on and/or control the degree of heat produced thereby for providing heat within interior chamber  4  as well as heat to PCM material  58  radiated through the various inner layers  68  of skin  54 . Temperature control unit  17  may also control refrigeration assembly  28  in response to the signal from temperature sensor  27  to control the degree of cooling provided thereby within interior chamber  4 , such as by turning it off or turning it on. Based on the signal from humidity sensor  31 , humidity control unit  19  controls the solenoid or other actuating mechanism for operating control valve  33  to increase or decrease the amount of moisture within interior chamber  4 . Similarly, based on the signal from CO 2  sensor  37 , CO 2  control unit  21  controls the solenoid or other actuating mechanism of control valve  39  in order to increase or decrease the amount of carbon dioxide entering interior chamber  4  in order to provide the appropriate level of CO 2  in accordance with the input settings. Fan assembly  23  may be operated to rotate the fan in order to gently blow the gas within interior chamber  4  to maintain a substantially uniform temperature, humidity and level of carbon dioxide throughout the chamber. Fan assembly  23  may be operated on a continuous basis or intermittently in a variety of predetermined patterns, which may be related to the opening and closing of door  5 , especially to help recover the internal temperature and the CO 2  and humidity levels after the door has been opened and closed. 
     PCM  58  of the present invention helps to maintain interior chamber  4  at a substantially constant temperature due to the significant amount of latent heat which PCM  58  absorbs or releases during its phase change, namely melting or freezing. PCM  58  is especially helpful in maintaining that temperature if there is a loss of power to the heating element  29  or refrigeration assembly  28  for an extended period. More particularly, PCM  58  is configured to have a melting or freezing phase change temperature which is at or about a desired selected temperature of interior chamber  4 . Thus, the storage item or items  40  may be placed in interior chamber  4  to help maintain the storage items near the phase change temperature of a given PCM  58  (block  161 ). Typically, the melting or freezing temperature of PCM  58  is within the range of about −40° C. (−40° F.) to about 150° C. (302° F.) or 160° C. (320° F.). However, the melting or freezing temperature of PCM  58  may be less or greater than this range. 
     In one embodiment, the melting temperature of PCM  58  is about 37° C. (98.6° F.) or in a range of 35-40° C. since this is one of the most commonly used temperatures for culturing bacteria and mammalian cells. One suitable phase change material which has a melting or freezing temperature of about 37° C. is available under the name “BioPCM Phase Change Material-37” from Phase Change Energy Solutions, Inc. of Asheboro, N.C. This product includes a phase change component and a fire suppression component. The phase change component is a derivative of fatty acids. The above noted business also produces PCMs which have respective melting or freezing temperatures anywhere within the range of about −40° C. to about 150° C. or 160° C. Similarly, phase change materials which are suitable for use as PCM  58  in the present invention are available from Entropy Solutions, Inc. of Minneapolis, Minn. Entropy Solutions, Inc. also produces a large variety of PCMs which have a respective melting temperature within the range of about −40° C. to about 150° C. or so. For example, one such PCM which melts or freezes at about 37° C. is available from Entropy Solutions, Inc. under the name “PureTemp 37.” Likewise, Entropy Solutions, Inc. produces other PCMs, such as “PureTemp −40” having a melting point of about −40° C., “PureTemp −12” having a melting point of about −12° C., “PureTemp 4” having a melting point of about 4° C., “PureTemp 23” having a melting point of about 23° C., “PureTemp 30” having a melting temperature of about 30° C., “PureTemp 40” having a melting point of about 40° C. and “PureTemp 50” having a melting point of about 50° C. This company also produces a much wider variety of PCMs, for example PCMs (with analogous names) which have melting or freezing points respectively of about −14° C., about 7° C., about 15° C., about 18° C., about 27° C., about 30° C., about 43° C., about 48° C., about 53° C., about 55° C., about 56° C., about 61° C., about 68° C., about 103° C. and about 151° C. Entropy Solutions, Inc. is capable of producing a PCM of substantially any desired melting temperature. Entropy Solutions, Inc. indicates that the PCMs which they produce are from vegetable-based fats and oils. It is noted, however, that any suitable phase change material having the desired melting temperature may be used as PCM  58 . 
     In some cases, it is desired to maintain the temperature of interior chamber  4  and item  40  at a temperature higher than room temperature (about 22 to 23° C. or 71 to 73° F.) or the ambient temperature, and thus PCM  58  is a solid at room temperature or at the ambient temperature. To take advantage of the phase change concept of such an embodiment of material  58 , heating element  29  is operated in order to heat interior chamber  4  and the phase change material  58  until it melts at its melting phase change temperature (block  160 ). Most preferably, all of PCM  58  is melted so that PCM  58  is able to provide the greatest duration of substantially constant temperature during its phase change from the liquid state to the solid state while there may be no additional heat source available to maintain the interior temperature of interior chamber  4 , such as during a power outage. In the heating scenario, each of the chambers positions the phase change material between the solid insulation and interior chamber  4 , or positions the phase change material within interior chamber  4  itself so that insulation  56  of the container and the insulation of door  5 A and/or the double paned window of door  5  substantially aids in preventing loss of heat from interior chamber  4 . 
     In other cases, it is desired to maintain the temperature of interior chamber  4  and item  40  at a temperature lower than room temperature or the ambient temperature, and thus PCM  58  is a liquid at room temperature or at the ambient temperature. Thus, refrigeration assembly  28  is operated in order to cool interior chamber  4  and the phase change material  58  to its freezing point or phase change temperature so that it freezes or solidifies (block  160 ). Most preferably, all of PCM  58  is frozen or solidified so that PCM  58  is able to provide the greatest duration of substantially constant temperature during its phase change from the solid state to the liquid state while there may be no additional cooling or refrigeration source available to maintain the interior temperature of interior chamber  4 , such as during a power outage. In the refrigeration scenario, the phase change material in the respective insulation chambers is positioned so that insulation  56  of the container and the insulation of door  5 A and/or the double paned window of door  5  substantially aids in preventing the transfer of external heat into interior chamber  4 . 
     Although PCM  58  is well suited to help maintain the temperature during a power outage, it also helps in a variety of other situations. For instance, PCM  58  helps maintain and/or expedite recovery of the desired temperature within interior chamber  4  during and after door  5  is opened ( FIG.  1   ) such as when item or items  40  are inserted and/or removed from interior chamber  4  (Arrows A in  FIGS.  2 ,  5 ,  7 - 11 ,  13   ). Further, PCM  58  helps maintain or expedite recovery of the desired temperature when the temperature in chamber  4  is otherwise changed (increased or decreased) due to such factors as electrical power fluctuations, gas injections such as injection of carbon dioxide via CO 2  control unit  21 , liquid injections such as injection of water via humidity control unit  19 , exothermic or endothermic reactions occurring within item or items  40 , and electronic devices which are part of an item  40 . Such an electronic device might be, for example, lighting equipment such as might be used to simulate sunlight for growing plants, such that the light would produce heat when turned on within chamber  4 . Another type of such an electronic device is a water pump for pumping water through an aqua tank, such as used for growing algae. Other examples of such an electronic device are a shaker for agitating a solution to facilitate growth, or a cell roller for rolling a bottle back and forth. Any of these electronic devices or others would during operation produce heat which would likewise tend to heat chamber  4  and any item therein. In addition, turning such electronic devices off while in chamber  4  would reduce the amount of heat energy that the electronic device produced within chamber  4  and thus alter the temperature in chamber  4 . Likewise, altering the operation of such electronic devices in particular ways may also change the amount of heat that the device produces within chamber  4  at a given time. PCM  58  thus helps to maintain and/or facilitate recovery of the desired chamber  4  temperature in all of these scenarios or any other situation which would affect the internal temperature of chamber  4 . 
     PCM  58  enhances the ability to maintain the stability of the temperature within chamber  4  as well as the uniformity of the temperature throughout chamber  4 . The use of PCM  58  also enhances humidity uniformity in chamber  4  in combination with the humidity controls of the insulated chambers of the present invention, such that a stable dew point can be created in chamber  4 , and the formation of condensation on items within chamber  4  or the walls defining chamber  4  can be minimized or eliminated. While the usefulness of PCM  58  has been described primarily as being related to its phase change characteristics, it is worth noting that PCM  58  also acts as an effective thermal mass and/or a thermal insulator. 
     It is also noted that other than PCM  58  and possibly the liquid medium  105 , the other components of the various insulated chambers of the present invention are not considered to be PCMs, but rather remain in a single state, typically solid, throughout the entire range of the operational parameters of the given insulated chamber. Thus, among the components that remain in a solid state over the entire operational parameter of the insulated chambers of the present invention are the skins of the container and door, the control assembly, the various layers of insulation  70  and the like, the various control units, sensors and control valves, the heating and cooling devices (other than the liquid refrigerant within the cooling device), glass panes of the door where used, the seals used between the panes and between the door and the container, the wire or other similar shelves, the outer skin of the PCM packets, the fan assembly, the solid matrix when used, and any other components which would obviously remain in a solid state during the normal operational parameters of the insulated chamber. 
     Although the various insulated chambers described herein are similar, the certain aspects of the configurations may be more suited to certain purposes. For example, the upper and middle packets  84  in chamber  1 B ( FIG.  7   ) are positioned below and adjacent the respective shelf  2  and item  40  thereon, which is better suited for when the desired temperature of chamber  4  and item  40  is above the ambient temperature. On the other hand, the upper packet  84  in chamber  1 C ( FIG.  8   ) is positioned above and adjacent the upper shelf  2  and upper item  40  thereon, which is better suited for when the desired temperature of chamber  4  and item  40  is below the ambient temperature. Generally, the PCM is distributed strategically to enhance natural convection, and thus more PCM is located toward the bottom of chamber  4  when the desired chamber  4  temperature and PCM melting temperature is above the ambient temperature, whereas more PCM is located toward the top of chamber  4  when the desired chamber  4  temperature and PCM melting temperature is below the ambient temperature. In addition, more PCM is typically positioned adjacent the door opening to offset the heat loss path created in this area. It is further noted that various of the thermally conductive materials used in the present invention enhance thermal conduction between the PCM and interior chamber  4  and between the PCM and components within chamber  4  including item  40 . In particular, layers  86  and  88  of packet  84  enhance such thermal conduction, as do inner layer  62  of skin  54  ( FIGS.  2 ,  3   ) and inner layer  80  of skin  74  of door  5 A ( FIG.  5   ). 
       FIG.  16    illustrates an additional advantage of using packets or shelves  84 A. More particularly, each shelf  84 A is removable from and insertable into interior chamber  4  with items  40  thereon within recesses  128 , as indicated at arrow F (block  161 ). Thus, a given packet  84 A may be removed from interior chamber  4  and placed at a position outside the interior chamber  4  such as on a support surface  156  while the storage items  40 , shown here as petri dishes  140 , and the contents thereof, remain seated on the shelf within recesses  128  (block  163 ). While the storage items  40  and/or shelves  84 A are removed from interior chamber  4 , various procedures may be undertaken with regard to the storage items, either while the storage items are on or removed from the given shelf  84 A or a similar shelf (block  164 ). Support surface  156  may, for example, be in the form of a table or a counter which is part of a fume hood whereby fumes from the petri dishes or other items under the hood may be exhausted. During the culturing of cells  152 , it is necessary for the cells to be fed a suitable food, as indicated at arrow G. Thus, a worker may feed the cells  152  on medium  150  while the petri dish is seated within recesses  128  on packet  84 A while the packet is on support surface  156  within a fume hood or the like. When the petri dishes are placed within recesses such as recesses  128 , or remain seated atop a PCM packet like packet  84  in  FIG.  6   , the PCM of the corresponding packet helps to maintain the desired temperature of the item  40 , including the medium  150  and cells  152  while they are outside the interior chamber  4  of insulated chamber  1 H or the like. In addition,  FIG.  16    illustrates that a given petri dish or other storage item  40  may be removed from the shelf or packet  84 A when both are outside interior chamber  4  in order that the storage item  40  may be manipulated for other purposes. For example, storage item  40  may be removed from the packet (arrow H) and seated on another support surface  158 . Support surface  158  also represents, for example, a scale on which item  40  may be weighed, or a microscope so that cells  152  or other components of item  40  may be viewed under the microscope. After a given item  40  has been manipulated on surface  158  or by any given tool as desired, it may be returned to the recess of packet  84  (arrow H) and other items  40  may similarly be removed and reinserted on packet  84 . Once all procedures involving storage items  40  have been performed outside the insulated chamber, packet  84  with the various items  40  may be reinserted into interior chamber  4  (block  165 ). 
     Each of the chambers of the present invention may also be configured with two or more PCMs each of which has a different melting or freezing point. Thus, for example, one or more of layers  72 A-E of chamber  1  ( FIGS.  2 - 4   ) or layers  72 A-F of chamber  1 A ( FIG.  5   ) may be formed of one PCM having a first melting or freezing phase change temperature while one or more of the other of said layers  72  may be formed of a PCM having a second melting or freezing phase change temperature which is different than the first melting or freezing temperature. Similarly, the layer  72 G within one of packets  84  of chambers  1 B or  1 C ( FIG.  7 - 8   ) may be formed of a PCM having the first melting or freezing temperature while another one of the layers  72 G of the corresponding chamber  1 B or  1 C is formed of a PCM having the second melting or freezing temperature. Likewise, the layers  72 A of chambers  1 D or  1 E ( FIGS.  9 - 10   ) may have the first melting or freezing temperature while the respective layer  72 B has the second melting or freezing temperature. Moreover, any one of the above noted PCM layers  72  may be formed of two or more different PCMs each having different melting temperatures. Whether these two or more PCMs are in separate layers or intermixed, the chamber thus provides the corresponding PCM for the respective first, second or third selected internal temperature of the interior chamber. In addition, the encapsulated pellets  104  of chambers  1 F and  1 G ( FIGS.  11  and  13   ) may include two or more batches of pellets  104  such that the PCM  58  within one batch has a melting or freezing phase change temperature which is different than that of the other batch or batches. Configuring the chambers to have PCMs with differing melting or freezing temperatures may be useful, for example, in the pharmaceutical industry. In particular, drug manufacturers run stability tests on various medicines respectively at 30° C. and 40° C. (104° F.). Thus, the chambers of the present invention may be configured with one PCM having a melting point of about 30° C. and another PCM having a melting point of about 40° C. to facilitate maintaining the temperature of interior chamber  4  at the corresponding temperature as desired by the user. The melting or freezing phase change temperatures of the two PCMs in the above example are both, for example, above 0° C. and above the typical ambient temperature or typical room temperature of about 22° C. or 23° C. However, two or more PCMs used with a given insulated chamber of the present invention may also be configured to have melting or freezing phase change temperatures which are both below 0° C., the ambient temperature or the room temperature noted above, or may also be configured such that the phase change temperature of one of the PCMs is above one of these reference temperatures and the other is below the corresponding reference temperature. 
     Thus, where the chamber utilizes two phase change materials each having different melting or freezing phase change temperatures, the chamber may be operated to either heat or cool the first phase change material with one of the heating or cooling devices carried by the chamber to melt or freeze the first phase change material at its melting or freezing temperature while also heating or cooling the interior chamber to that temperature and incubating, storing or maintaining a given item within the interior chamber at about this first melting or freezing temperature. Subsequently, the chamber may be similarly operated to heat or cool the second phase change material and the interior chamber at a second melting or freezing phase change temperature of the second phase change material such that it melts or freezes. Then, either the item that was incubated, stored or maintained at the first temperature may also be incubated, stored or maintained at the second temperature (block  166 ), or it may be removed and another item may be inserted into interior chamber  4  (block  167 ) and incubated, stored or maintained at or near the second temperature (block  168 ). It is noted that the processes illustrated in  FIG.  17    do not necessarily occur in the order shown nor are the processes necessarily separate as might be suggested by the arrows. 
     One aspect of the present invention relates to a novel and non-obvious method and system employing a new H2O2 cycle to decontaminate cell culture incubators. One advantageous feature of the current invention comprises a H2O2 cleaning cycle that consolidates two steps in the prior art into one step thereby advantageously shortening the H2O2 cleaning cycle. Another advantageous feature of the current invention comprises a H2O2 cleaning cycle with a shortened sterilization step, relative to the sterilization step of the prior art cleaning cycle. In addition to reducing the number of steps, the present invention employs a ‘dry’ H2O2 cycle, distinguishing it from the prior art ‘wet’ cycles. 
       FIG.  19    is a front elevational view of an embodiment of a system  202  for vaporized hydrogen peroxide cleaning of an incubation chamber. The system  202  includes the container  3  discussed in the above embodiments, and a module  200  positioned on a shelf  2  of the container  3  for vaporized hydrogen peroxide cleaning of the incubation chamber  4  of the container  3 . In one embodiment, the material  40  has been removed from the shelves  2  and replaced by the module  200 . As depicted in the embodiment of  FIG.  19   , the module  200  is communicatively coupled to the power source  25  and the control interface  15 , to perform various steps of the method for vaporized hydrogen peroxide cleaning of the incubation chamber  4  of the container  3 , as discussed in greater detail below. 
     In some embodiments, the container  3  of the system  202  does not include any PCM material. In other embodiments, the container  3  of the system  202  includes PCM material, including any one of the arrangements of PCM material discussed above in the above embodiments of  FIGS.  1 - 17   . In one example embodiment, the container  3  of the system  202  includes an arrangement of PCM material that is similar to the embodiment of  FIG.  5   , the embodiment of  FIG.  9    or some combination thereof. In another example embodiment, the container  3  of the system  202  includes a combination of the embodiments of  FIG.  5    and  FIG.  9   , specifically a heating element  29  inside the chamber  4  ( FIG.  5   ) and a heating element  29 A between the insulation  56  and the PCM  72  ( FIG.  9   ). In this example embodiment, the heating element  29  inside the chamber  4  is provided to quickly achieve elevated incubator air temperature within the chamber  4  and the heating element  29 A is provided to melt the PCM material  72  and is used for steady state control during the H202 cleaning process. 
     Although the system  202  depicts the module  200  positioned within the container  3 , the module  200  and method for vaporized hydrogen peroxide cleaning of an incubation chamber is not limited to use with any particular incubator, such as the container  3 . In one embodiment, the specific temperature levels, the humidity levels and the time periods of each step of the method discussed herein will vary, depending on one or more parameters of the incubator, such as the size of the interior chamber and concentration of H202 solution. Additionally, in other embodiments, the components of the system  202  can vary, depending on one or more parameters of the incubator. In an example embodiment, more than one temperature sensor  27  and/or more than one humidity sensor  31  and/or more than one module  200  may be positioned within the chamber  4 , depending on the size of the interior chamber  4 . The numerical parameters of the method discussed herein are merely one example embodiment of the method for vaporized hydrogen peroxide cleaning of the interior chamber  4  of the container  3  using the module  200  and thus the method using the module  200  with other incubators with different sized chambers will have different temperature levels, humidity levels and time periods than those discussed herein. In one example embodiment, the container  3  is sized such that the dimensions of the interior chamber  4  are 31.3″ width (from left side to right side), 9.5″ depth (from back to front) and 26″ height, with an approximate volume of 5 ft 3 . In another example embodiment, the container  3  is sized such that the dimensions of the interior chamber  4  are 32″ width, 27″ depth and 52.7″ height, with an approximate volume of 25 ft 3 . In another example embodiment, the container  3  is sized such that the dimensions of the interior chamber  4  are 32″ width, 27″ depth and 65.7″ height, with an approximate volume of 33 ft 3 . In another example embodiment, the container  3  is sized such that the dimensions of the interior chamber  4  are 23″ width, 25.8″ depth and 29.8″ height, with an approximate volume of 10 ft 3 . In still other embodiments, the container  3  is sized such that the dimensions of the interior chamber  4  include a width in a range of 23-32″, a depth in a range from 9-27″ and a height in a range from 26-66″. However, the embodiments of the container  3  are not limited to interior chambers  4  with these specific numerical dimensions or dimensional ranges. 
       FIGS.  20 A- 20 B  are front perspective views of one embodiment of the module  200  for vaporized hydrogen peroxide cleaning of the incubation chamber  4 .  FIG.  20 A  shows a handle  230  of the module  200  in a closed position and a front end  231  of the module  200  in a closed position  232 , based on the handle  230  in the closed position.  FIG.  20 B  shows the handle  230  moved from the closed position of  FIG.  20 A  to an open position, which in turn causes the front end  231  to move upward to an open position  233  and reveal a receptacle  236 . In an embodiment, the receptacle  236  is sized to receive a cartridge  234  of H202, such as 35% H202 for vaporized injection in the chamber  4 . In some embodiments, the H202 concentration of the cartridge  234  is in a range of 30-40%. In other embodiments, the H202 concentration of the cartridge  234  is in a range from 15-65% and in another embodiment, the H202 concentration of the cartridge  234  is in a range from 25-59%. In an embodiment, the cartridge  234  is disposable after each cleaning cycle. The module includes an injection item for injecting H202. In some embodiments, the injection item is a piezo ultrasonic device  235  that is positioned over the receptacle  236 . After the cartridge  234  is inserted in the receptacle  236  and the piezo ultrasonic device  235  receives a signal to initiate the injection cycle, the piezo ultrasonic device  235  commences to inject the vaporized H202 from the cartridge  234  and into the incubator chamber where the module  200  is positioned. The injection item is not limited to the module  200  or the piezo ultrasonic device  235  and includes any injection item known to one of ordinary skill in the art that is capable of injecting vaporized H202. 
       FIGS.  21 A- 21 B  are rear perspective views of the embodiment of the module  200  of  FIGS.  20 A- 20 B . The end  240  of the module  200  includes a grating or vent  241 . A removable piece  242  of the end  240  can be detached to expose a catalyst  244  mounted within the module  200 , such as a silver catalyst, for example. In one embodiment, during one stage of the cleaning cycle, air containing H202 within the interior chamber  4  is passed through the silver catalyst  244  and through the vent  240  to reduce the level of H202 in the air within the interior chamber  4 . Upon passing through the silver catalyst  244 , the H202 in the air is converted to vaporized H20 and 02. 
       FIGS.  22 A- 22 B  are perspective views of one embodiment of the catalyst  244  and fan  246  positioned within the module  200  of  FIGS.  21 A- 21 B . In one embodiment, the silver catalyst  244  is mounted on a frame  245  and securely fixed within the module  200  between a fan  246  and the vent  241 . In this embodiment, during a phase of the cleaning cycle discussed herein, in order to reduce a level of H202 within the interior chamber  4 , air is drawn into the module  200  by the fan  246  and through the silver catalyst  244  to reduce a level of H202 in the air before the air is exhausted through the vent  240  back into the interior chamber  4 . As shown in  FIGS.  22 A- 22 B , the module  200  includes wiring  248  (positive and ground cables) that are respectively coupled at respective connections  250   a ,  250   b  in order to apply a voltage across the catalyst  244  and measure one or more electrical properties of the silver catalyst  244 , such as electrical resistance, for example. In this example embodiment, the measurement of the one or more electrical properties is used to indicate whether or not the silver catalyst  244  has remaining useful life and thus can still effectively reduce the level of H202 in air passed through the catalyst  244  by the fan  246 . 
       FIG.  23    is a partial block diagram of the embodiment of the system  202  of  FIG.  19   . Indeed, the block diagram of  FIG.  23    does not depict all components of the system  202  involved in the H202 cleaning cycle of the interior chamber  4  of the container  3 , as other drawings (e.g.  FIG.  1   ) depict other such components and will be discussed herein. 
       FIG.  24    depicts a flowchart of a method  400  for operating the system  202  during an H202 cleaning cycle. Although steps are depicted in  FIG.  24    as integral steps in a particular order for purposes of illustration, in other embodiments, one or more steps, or portions thereof, are performed in a different order, or overlapping in time, in series or in parallel, or are omitted, or one or more additional steps are added, or the method is changed in some combination of ways. In step  401 , prior to initiating the H202 cleaning cycle, contents (e.g. the material  40 , see  FIG.  1   ) is removed from the shelves  2  of the container  3 . In step  402 , a full H202 cartridge  234  is loaded into the module receptacle  236 . In step  403 , the module  200  is then positioned on a shelf  2  in the interior chamber  4  of the container  3 , as shown in  FIG.  19   . In step  405 , the module  200  is then connected to the power source  25  and control interface  15  of the container  3 , as shown in  FIGS.  19  and  23   . 
     In step  407 , in one embodiment, once the control interface  15  detects the module  200 , the control interface  15  is configured to determine whether the catalyst  244  is present and has remaining useful life. In an embodiment, each catalyst  244  has 100 or more useful cycles. As shown in  FIG.  23   , in this embodiment, the control interface  15  transmits a signal to the power source  25  to apply a voltage with the wiring  248  across the connections  250   a ,  250   b  and measures a resistance across the catalyst  244 . In one embodiment, the control interface  15  is communicatively coupled to an ohmmeter  243  that measures the resistance across the catalyst  244  and receives a signal of the measured resistance from the ohmmeter  243 . Based on the measured resistance of the catalyst  244 , the control interface  15  determines whether the catalyst  244  has remaining useful life (e.g. is in good working condition) and thus can effectively convert the H202 content in air passed through the catalyst  244  to water (H20) and oxygen gas (O2). In some embodiments, the control interface  15  determines that the catalyst  244  has remaining useful life if the measured resistance is less than a threshold resistance. In an example embodiment, the threshold resistance is 300 ohms. However, the threshold resistance is not limited to this numerical value and may vary depending on one or more characteristics of the catalyst. In an example embodiment, a low voltage DC current source is used to measure the catalyst resistance. In addition to verifying useful life of the catalyst  244 , step  407  is employed to verify the presence of the catalyst  244 . In some embodiments, a sensor is provided to sense the presence of the catalyst  244  and transmits a signal to the control interface  15  based on whether the catalyst  244  is present. In this embodiment, the control interface  15  determines that the catalyst  244  is present, based on the received signal from the sensor. 
     In step  409 , if the control interface  15  determines that the catalyst  244  does have remaining useful life and is present, the control interface  15  prompts the user to initiate the H202 cleaning cycle using one or more buttons (see  FIG.  19   ) on the control interface  15 . In other embodiments, the control interface  15  automatically initiates the H202 cleaning process after steps  405  and  407 . If the control interface  15  determines that the catalyst  244  does not have remaining useful life or is not present, the control interface  15  outputs this determination and will not prompt the user to initiate the H202 cleaning cycle or initiate the H202 cleaning cycle. In one embodiment, the control interface  15  is configured to prevent an initiation of the H202 cleaning cycle until the control interface  15  has determined that the catalyst  244  has remaining useful life and is present. 
     Additionally, in step  411 , in an example embodiment, at the same time that the user presses the button on the control interface  15  to initiate the H202 cleaning cycle, the control interface  15  transmits a signal to a door lock  252  ( FIG.  19   ,  FIG.  23   ) to lock the door  5  of the container  3  during the H202 cycle. However, step  411  is not limited to this arrangement. In other embodiments, the door lock  252  is a manual mechanical door lock that is manually engaged by the user in step  411  after the user initiates the H202 cleaning cycle in step  409 . In still other embodiments, no door lock  252  is used and thus step  411  is not performed. In this example embodiment, the door lock  252  remains engaged and thus the door  5  remains locked until completion of the H202 cleaning cycle (e.g. until the level of H202 in the interior chamber  4  reaches a safe level, as discussed below), at which time the control interface  15  transmits a signal to the lock  252  to disengage the lock  252  so that the door  5  can be opened. However, the door lock  252  and step  411  are merely optional features and need not be included in the system  202  or method  400 . In other embodiments, the control interface  15  performs other safety measures after the H202 cleaning cycle is initiated, including flashing a colored warning sign on the interface  15  to caution the user not to open the door  5  of the container  3  during the H202 cycle. In another embodiment, if the control interface  15  detects that the door  5  is opened during the H202 cycle, the control interface  15  initiates an alarm. In another embodiment, the control interface  15  features an “abort” option, which the user can press which causes the control interface  15  to jump to a final step of the H202 cleaning cycle (e.g. step  507  as discussed below). 
       FIG.  25    depicts a flowchart of a method  500  for performing the H202 cleaning cycle of the interior chamber  4  with the module  200 . Although steps are depicted in  FIG.  25    as integral steps in a particular order for purposes of illustration, in other embodiments, one or more steps, or portions thereof, are performed in a different order, or overlapping in time, in series or in parallel, or are omitted, or one or more additional steps are added, or the method is changed in some combination of ways. In step  501 , after the user presses the button on the control interface  15  to initiate the H202 cleaning cycle (step  409 ), the control interface  15  transmits a signal to the temperature control unit  17  (see  FIG.  19   ) to raise the temperature within the interior chamber  4  to a sterilization temperature (e.g.  37 C). The temperature control unit  17  activates the heating device  29  ( FIG.  19   ) until the measured temperature by temperature sensor  27  is at the sterilization temperature. In some embodiments, the temperature control unit  17  is incorporated into the control interface  15  and thus the control interface  15  transmits a signal to the heating device  29  to raise the temperature within the interior chamber  4  until the measured temperature reaches the sterilization temperature. 
     Additionally, at the same time that the control interface  15  signals the temperature control unit  17 , in step  503  the control interface  15  transmits a signal (see  FIG.  23   ) to an injection item (e.g. the piezo ultrasonic device  235 ) within the module  200  to initiate injection of vaporized H202 (e.g. 35%) from the cartridge  234  into the interior chamber  4 . In a first embodiment of injecting the H202, a humidity sensor  31   a  (see  FIG.  19    and  FIG.  23   ) is positioned within the interior chamber  4  to measure a combined humidity of H202 and H20 in the air. After the piezo ultrasonic device  235  receives the signal from the control interface  15 , the piezo ultrasonic device  235  commences to inject vaporized H202 into the air within the chamber  4  which increases the combined humidity of H202 and H20. The humidity sensor  31   a  continuously measures the combined humidity of H202 and H20 within the chamber  4  and transmits a signal to the control interface  15  to communicate the measured combined humidity. When the combined humidity within the chamber  4  reaches a sterilizing level (e.g. 90%), the control interface  15  sends a signal to the piezo ultrasonic device  235  to cease the injection of H202 within the chamber  4 . 
     In a second embodiment of injecting H202, a predetermined humidity injection profile is stored in a memory of the control interface  15 . In some embodiments, the predetermined humidity injection profile includes a specified percentage ‘on-time’ of the injection system (e.g. injection rate) that varies over time. The percentage ‘on-time’ of the injection system represents a percentage or ratio of the time period that the injection item (e.g. piezo ultrasonic device  235 ) is activated. In an example embodiment, the injection profile approximates the injection profile of the first embodiment of injecting H202 discussed above. This second embodiment of injecting H202 is advantageously less expensive than other methods of injecting H202. In some embodiments, the percentage ‘on-time’ of the injection item (e.g. piezo ultrasonic device  235 ) is related to the temperature in the chamber  4  over time. In an example embodiment, the percentage ‘on-time’ of the injection item is related to the temperature in the chamber  4  as: 
       %=1.06× T− 22  (1)
 
     where % is the percentage ‘on-time’ of the injection item to maintain 90% relative humidity in the chamber  4  and T is the temperature of the air in the chamber  4  (in units of Celsius, C). In one embodiment, the memory of the control interface  15  includes equation 1 and the memory of the control interface  15  computes the percentage ‘on-time’ of the injection item based on an input temperature T of the chamber  4  from the temperature sensor  27 . During the first time period  212  (see below), the control interface  15  signals the injection item (e.g. piezo ultrasonic device  235 ) in accordance with this computed percentage ‘on-time’, so that the injection item remains on for the computed percentage of the first time period  212 . In a third embodiment of injecting H202, a pair of humidity sensors  31   a ,  31   b  are provided within the chamber  4 , where the humidity sensors  31   a ,  31   b  are similar with the exception that the humidity sensor  31   b  includes a filter to remove H202 from the measured air and thus the humidity sensor  31   b  only measures the relative humidity of H20 in the air. In an example embodiment, the filter is a catalyst  249  that functions in a similar manner as the catalyst  244  (e.g. removes H202 from air passed through the catalyst). This third embodiment of injecting H202 is similar to the first embodiment of injecting H202, with the exception that the additional humidity sensor  31   b  advantageously provides additional data (e.g. level  222  in  FIG.  26    discussed below) including the relative humidity of only the H20 in the air. In an embodiment, a relative humidity of only the H202 in the air can be determined by subtracting the level of sensor  31   b  from the level of sensor  31   a . In an example embodiment, the relative humidity of only the H202 in the air is increased to a range from 20-30%. In some embodiments, the relative humidity of only the H202 during the second time period  216  (e.g. sterilization) is a dependent variable on the combined humidity  224  (e.g. 90%) during sterilization. 
     These steps  501  and  503  of the H202 cleaning cycle are depicted in the first time period  212  of the graph  204  of  FIG.  26   . The temperature  220  within the interior chamber  4  is depicted as increasing from an initial temperature  226  (e.g.  25 C) to the sterilizing temperature (e.g.  37 C) over the first time period  212 . Additionally, during the same time period  212  a combined relative humidity  224  of H20 and H202 increases from an initial humidity  228  (e.g. based on the injection of H202 from the module  200  into the chamber  4 ) to a sterilizing level (e.g. 90%). This is distinct from the prior art H202 cleaning cycle ( FIG.  18   ) where two separate steps are required (e.g. the first time period  312  of 10 minutes to raise the temperature and the second time period  314  of 5 minutes to raise the humidity of H202). The H202 cleaning cycle advantageously performs both of these steps in one step that lasts time period  212  (e.g. 10 minutes) that is shorter than the combined time periods  312 ,  314  (e.g. 15 minutes) of the prior art H202 cycle. 
     In step  505 , after the end of the time period  212 , the sterilizing temperature  220  and sterilizing combined humidity  224  are maintained within the interior chamber  4  over a minimum time period (e.g. a second time period  216 , see  FIG.  26   ). In one embodiment, the second time period  216  is 12 minutes. In this step  505 , the control interface  15  transmits a signal to the temperature control unit  17  and humidity control unit  19  such that the sterilizing temperature  220  and sterilizing combined humidity  224  are maintained for the second time period  216 . Additionally, the humidity sensor  31   a , the control interface  15  and piezo ultrasonic device  235  continuously communicate over the minimum time period in order to maintain the sterilizing level of the combined humidity within the chamber  4  during step  505 . For example, if the combined humidity of H202 and H20 drops from the sterilizing level, the control interface  15  transmits a signal to the piezo ultrasonic device  235  to inject vaporized H202 within the chamber  4  until the control interface  15  receives a signal from the humidity sensor  31   a  that the combined humidity is back at the sterilizing level, at which time the control interface  15  transmits a signal to deactivate the piezo ultrasonic device  235 . In some embodiments, the time period  216  of the sterilizing step (e.g. 9 minutes) is shorter than the time period  316  of the sterilizing step (e.g. 11 minutes) in the prior art cycle  300 . 
     In step  507 , after the end of the second time period  216 , the H202 cleaning cycle enters an inactivate step, where the level of H202 within the interior chamber  4  is reduced to safe levels. At the beginning of a third time period  218  of the step  507  (see  FIG.  26   ), the control interface  15  transmits a signal to the fan  246  (see  FIG.  23   ) to draw air from the interior chamber  4  into the module  200 , passing the air through the catalyst  244  to reduce a level of H202 in the air, before directing the air back into the interior chamber  4  through the vent  240 . In an example embodiment, the catalyst  244  is configured to reduce the H202 content within the air to vaporized water (H20) and oxygen gas (O2). In one embodiment, the control unit  15  activates the fan  246  during step  507  for the third time period  218  (e.g. 20 minutes) until the level of H202 reaches a safe level, as discussed in greater detail below. In one embodiment, once the control unit  15  confirms that the level of H202 has lowered to a safe value, the control unit  15  transmits a signal to the door lock  252  to disengage to lock  252  so that the door  5  can be opened. 
     The inventive H2O2 cleaning cycle is illustrated in the graph  204  of  FIG.  26   . Horizontal axis  260  is time in units of minutes. Left vertical axis  262  is temperature in units of Celsius (C). Right vertical axis  264  is relative humidity in percentage (%). According to this cycle, the ‘dehumidification’ and ‘conditioning’ steps of the prior art cycle  300  (during time periods  312 ,  314 ) are combined into one time period  212  that is shorter than the combined time periods  312 ,  314 . As this inventive process begins the interior chamber  4  is heated and the temperature  220  begins to rise during the first time period  212  from an initial temperature  226  (e.g.  25 C). As the temperature  220  increases the air will have a greater moisture capacity. Then a small amount of H202 is injected into the interior chamber  4  during the first time period  212 . This amount of moisture is controlled to a desired sterilizing level (e.g. 90%), as discussed in step  501  above. The temperature  220  continues to rise as the H202 is injected to the chamber  4  during the first time period  212 . Again, this allows the air to handle more moisture and thus more H202 is injected. These small drying &amp; injection steps continue until the temperature  220  has reached a sterilizing temperature (e.g. 37 C). Once the temperature  220  stops increasing, the amount of moisture the air can hold also stops increasing. 
     In one embodiment, a process that took fifteen minutes (that is, the first time period  312  of ten minutes for the dehumidification step and the second time period  314  of five minutes for the conditioning step) in the prior art now takes only the first time period  212  which is less (e.g. ten minutes) than the combined first and second time periods  312 ,  314  in the prior art. In fact, because the conditioning segment of the dehumidification plus conditioning step takes only about five minutes, the humidity  224  reaches 90% before the temperature  220  reaches 37 C. See  FIG.  26   . This is distinct from the prior art method, where the humidity  324  reaches 90% after the temperature  320  reaches 37 C (See  FIG.  18   ). 
     According to this inventive H2O2 cycle  204 , heat is used to dehumidify the chamber interior  4 ; mechanical refrigeration is not used. Combining the two steps would not result in a beneficial outcome if dehumidification by mechanical refrigeration was used because that dehumidification process also removes H2O2 from the air. Of course, removal of H2O2 by the mechanical dehumidification would be detrimental as during the combined dehumidification and conditioning step H2O2 is being injected into the chamber  4 . 
     At the beginning of the H2O2 decomposing step (i.e. at the beginning of the third time period  218 ), the fan  246  is turned on in the chamber  4  that blows air through a silver catalyst, typically in the form of a silver mesh. The catalyst converts the H2O2 to harmless H2O and O2. This fan  246  is distinct from the fan  23 . 
     In addition to the overall shorter H2O2 cycle due to combining the first two steps, there is also more microbial ‘killing’ when the sterilization cycle begins. As soon as H2O2 is injected into the chamber  4 , microorganisms begin to die. In the prior art H2O2 cycle, H2O2 injection was begun after an elapsed time of ten minutes (e.g. after the first time period  312 ). 
     In the inventive H2O2 cycle, H2O2 is injected immediately (e.g. at the commencement of the first time period  212 ) and therefore immediately begins to have an effect. In theory, this allows for a shorter sterilization cycle (e.g. a shorter second time period  216 ). However, in one embodiment, the sterilization time period is not reduced, relative to the sterilization time period in the prior art cycle. In other embodiments, the second time period  216  is shorter than the third time period  316  of the prior art cycle of  FIG.  18   . 
     In one embodiment, during the time interval  218  of the inventive H2O2 cleaning cycle air is blowing through the silver mesh  244 . 
       FIG.  27    is similar to  FIG.  26    but includes additional detail including separately identifying safety factor time sub-intervals that are subsumed within the time intervals illustrated in  FIG.  26   . These safety factors are indicated as a single value or a range of values. 
     In the embodiment of  FIG.  27   , a safety factor of about ten minutes is applied during the dehumidification and conditioning step (e.g. first time period  212 ), noting a relative humidity during this step of 30-100%. The inventors recognize that starting conditions for each H2O2 cycle will vary with each use. Some users may begin with their incubator at ‘off’ at room temperature of 20 C. Other users may have been running the incubator and it is therefore already at an elevated temperature (i.e., above room temperature, such as  25 C as shown in  FIG.  3   ). Because the starting conditions vary, the amount of biological ‘kill’ during this phase will also vary. In this embodiment, the inventors have estimated and therefore included a relative humidity safety factor (SF) of between 30% SF and 100%. This SF between 30% and 100% indicates that the combined dehumidification and condition step discussed herein over the first time period  212  is sufficient to destroy between 30% and 100% of the microorganisms needed to achieve sterilization. In some embodiments, one or more biological indicators (BI&#39;s) are placed inside the chamber  4  prior to the dehumidification and condition step (i.e. prior to the first time period  212 ) and then the number of killed BI&#39;s is assessed after the first time period  212  (and prior to the sterilization interval  216 ). In some embodiments, this assessment of the BI&#39;s was performed over a variety of starting conditions, and the SF was calculated based on the resulting range of BI assessments. The embodiments of the invention are not limited to this SF and may have a wider or narrower SF, for example. 
     In the embodiment of  FIG.  27   , the sterilization interval  216  is shown as comprising two sub-intervals  216   a ,  216   b ; the first interval  216   a  (e.g. six minutes) and the second interval  216   b  (e.g. 3 minutes). The first interval  216   a  provides a log-6 kill, which by definition results in a sterilized environment. This metric results in the statistical destruction of all microorganisms and their spores, defined as 6 logs (10{circumflex over ( )}6) or a 99.9999% reduction. Statistically an environment sterilized to this level is considered to have zero viable organisms surviving. 
     However, again the inventors recognize the need to compensate for chamber variations and have therefore added a safety factor to the sterilization interval. In one embodiment a 50% safety factor, equivalent to the second interval  216   b  (e.g. three minutes or 50% of six minutes) that is 50% as long as the first interval  216   a  is used. 
     However, the sterilization interval is not limited to the interval  216   a ,  216   b  depicted in  FIG.  27   .  FIG.  28    depicts another embodiment of a sterilization interval  216 ′ that provides a log-12 kill, that is based on a doubling of the log-6 kill time  216   a  (e.g. six minutes), resulting in 12 minutes. The 50% safety factor interval (e.g. six minutes or 50% of twelve minutes) was added to the 12 minutes, resulting in a total 18 minute time period for the sterilization interval  216 ′. 
       FIG.  27    includes a reference to a H202 level (e.g. 75 ppm) during the time period  218  of the inactivate cycle. The time period  218   a  is based on the amount of time it takes to reduce the H202 to this level. This H202 level value, which is also applied in the  FIG.  26    although not labeled on  FIG.  26   , represents the IDLH (Immediate Dangerous to Life or Health) limit as defined by OSHA (Occupational Safety and Health Administration). In theory, when the H202 in the chamber  4  has been reduced to this H2O2 level the user can open the chamber door  5  as the air in the interior environment is safe. In fact the concentration would be diluted with room air, causing the level to drop by half in a few seconds. However, in one embodiment, the inventors have selected to add an additional time period  218   b  to the time period  218 , to inactivate to at least 150% more than IDLH level before the door  5  can be opened. In other embodiments, the inventors have selected to inactivate to a level where it is safe for the operator to open the door. The safety factor has been added to ensure that the level of H2O2 has been reduced to a safe value. Again, the safety factor compensates for chamber variations and tolerances, such as instrumentation measurement accuracy. 
     However, the time period of the inactivate cycle is not limited to the time periods  218   a ,  218   b  depicted in  FIG.  27   .  FIG.  28    depicts another embodiment of a time period  218 ′ of an inactivate cycle that provides a minimum time period (e.g. 60 minutes) for the inactivate cycle that is greater than the combined time periods  218   a ,  218   b . In some embodiments, after the time period  218 ′ has elapsed and humidity sensors verify that the H202 level is below a safe level, the door can be opened. 
     The inventive H2O2 cycle (including the indicated safety factors) is shorter (e.g. seven minutes shorter) than the prior art cycles. In an embodiment, the first time period  212  is shorter (e.g 5 minutes) than the combined time periods  312 ,  314  of the prior art cycle  300 , where the first time period  212  combines the dehumidification (time period  312 ) and conditioning (time period  314 ) steps of the prior art cycle  300 . In another embodiment, the sterilization time period  216  is shorter (e.g. 2 minutes) than the sterilization time period  314  of the prior art cycle  300 . This shortened sterilization time period  216  is attributable to injecting H202 into the chamber  4  at an earlier stage (first time period  212 ) in the inventive H202 cycle than at a later stage (second time period  314 ) in the prior art cycle  300 . Thus, a greater number of microorganisms are killed prior to the sterilization time period  216  in the inventive cycle than the sterilization time period  316  in the prior art cycle  300 . Accordingly, the sterilization time period  216  need not be as long in the inventive H202 cycle as the sterilization time period  316  in the prior art cycle  300 . This reduced cleaning cycle time is advantageous for the chamber user as the reduction in cleaning time allows for additional time to be devoted to culturing cells within the chamber  4 . 
     Certain other features of incubation chambers are described in commonly-owned patent applications that are incorporated herein by reference: application entitled Insulated Chamber with Phase Change Material and Door with Controlled Transparency, filed on Jul. 23, 2015 and assigned application No. 62/195,960; and application entitled Insulated Chamber with Phase Change Material, filed on Mar. 9, 2015 and assigned application Ser. No. 14/641,607. 
     In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed. 
     Moreover, the description and illustration of the invention is an example and the invention is not limited to the exact details shown or described.