Abstract:
An animal euthanasia device includes a chamber with an opening through which a partitioned cage may be wheeled. A pivotally attached door seals the opening using fixed edge seals and an inflatable door threshold seal. A latch secures the door, once closed. After a sensor verifies door closure, an electro-magnetic lock prevents inadvertent door opening during the process, which may be automated using a programmable logic controller (PLC). The PLC coordinates actuation of a fan and damper within an air exhaust opening, a fan and a damper within an exhaust gas opening, and a damper within a fresh air inlet opening, and also triggers a solenoid valve that controls flow of euthanizing gas into the chamber. A keyed selector switch controls power to the device to initiate the automated process, which is monitored using oxygen sensors, and CO2 flow and pressure sensors, and is reported on a human machine interface.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to improvements in apparatus for euthanizing animals, and more particularly to apparatus which are capable of safely and effectively euthanizing a large animal or a large number of animals in an automated process. 
       BACKGROUND OF THE INVENTION 
       [0002]    Many reasons arise which necessitate that the life of an animal must be terminated with minimal pain and distress. The reasons for euthanasia may include the diagnosis of an incurable disease such as cancer, painful medical conditions, broken limbs, exposure to the rabies virus, deterioration and impairment due to old age, and/or dissection and analysis of animals used in laboratory experimentation. There are a number of methods for performing euthanasia on various different animals, and many organizations promulgate standards for these procedures, including those of the American Veterinary Medical Association—The AVMA Guidelines on Euthanasia. These methods may generally be categorized as Physical Methods (e.g., penetrating captive bolt, shotgun, . . . ), Non-inhalant Pharmaceutical Agents (Barbiturates, Potassium Chloride, . . . ), and Inhalant Agents (e.g., Carbon Dioxide, Nitrogen, Argon . . . ). In many instances it is desirable to terminate the animals with inhalant agents. Furthermore, it is advantageous in many instances to terminate multiple large-sized animals at the same time, preferably within their own cages. Although there have been a number of devices heretofore developed to assist operators in euthanizing animals, they fail to fully accommodate performance of the process in strict accordance with many guidelines necessary to safely complete the procedure—both for the safety of the operator, and for the safe and humane treatment of the animals to be terminated. The apparatus of the present invention overcomes many of the disadvantages of the prior art, which will become apparent in the subsequent discussion. 
       OBJECTS OF THE INVENTION 
       [0003]    It is an object of the invention to provide apparatus necessary to safely euthanize an animal. 
         [0004]    It is another object of the invention to provide an apparatus that may be used to euthanize a plurality of large animals simultaneously. 
         [0005]    It is a further object of the invention to provide an automated apparatus that may be used to safely euthanize animals. 
         [0006]    It is another object of the invention to provide such automation that may be adjustable to safely euthanize various different species of animals. 
         [0007]    It is also an object of the invention to provide such automation that may be adjustable to safely euthanize animals in accordance with different standards. 
         [0008]    Further objects and advantages of the invention will become apparent from the following description and claims, and from the accompanying drawings. 
       SUMMARY OF THE INVENTION 
       [0009]    A device for euthanizing animals may include a specially constructed chamber with a door securable over an opening to the chamber cavity, being sealable on three sides against a door seal. The bottom of the opening of the chamber may have a threshold, over which a specially constructed cart/cage combination may be wheeled into the chamber cavity. The bottom of the door may therefore have an inflatable seal that may seal against the bottom of the door with respect to the threshold and the other door seal(s). A door latch is usable to secure the door in the closed position, and an electro-magnetic lock may additionally guard against unintentionally opening of the door during the process. A proximity switch may detect proper positioning of the cage/cart combination within the chamber, and one or more additional sensors may be used for verifying that the door is closed and locked. 
         [0010]    A supply valve may control the flow of a euthanizing gas into the chamber, which may be heated by a heater to suitable temperatures. The supply valve may operate in conjunction with a fan and damper secured in a fresh air exhaust opening in the chamber that may simultaneously permit the outflow of fresh air to prevent over-pressurization, which may otherwise cause distress to the animals therein. To safely access the cart/cage combination and facilitate its removal after the process has been completed, a fan and a damper secured within an exhaust gas opening in the chamber, and a damper secured within a fresh air inlet opening may work in conjunction to duct the toxic gas out of the chamber and be replaced with fresh air. The valves and damper may each be electromagnetically actuated using a solenoid. 
         [0011]    Electrical power to the device may be controlled by a keyed selector switch, and automation of the process may be overseen through the use of a programmable logic controller and a human machine interface (HMI), which may include a touch screen permitting adjustments to various set points in the procedure, for different species of animals (e.g., gas flow rates, concentrations of the euthanizing gas to induce narcosis, holding times, etc.). An emergency handle on the interior of the chamber may initiate immediate cessation of the introduction of gas into the chamber, and trigger the introduction of fresh air therein, as well as the unlocking of the chamber door. 
         [0012]    Oxygen sensors may be used for monitoring the concentration of euthanizing gas in the chamber, which may, for example, be CO2. (Note that the use of CO2 hereinafter is not intended to limit the possible choices of euthanizing gas that may be usable with the apparatus of the present invention, and is merely used to be exemplary). The concentration of the euthanizing gas within the chamber that is detected by the oxygen sensors may enable the PLC to precisely cease the flow of CO2 upon reaching a concentration needed to produce unconsciousness in the animal(s). A translucent observation window fixedly secured in one of the walls of the chamber may be used to verify unconsciousness. Subsequently, the concentration of gas may be increased to a level toxic for the particular animal(s). 
         [0013]    The cart-cage combination may be specially constructed to permit the animals to be housed and raised therein, and may include water supply lines, and access areas for trays to gather feces for lab analysis and research. A complete life-cycle for the particular animals may occur within the cart/cage combination, including euthanization in the chamber, at the end of successful experimentation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a piping and instrumentation diagram representing the apparatus of the present invention. 
           [0015]      FIG. 2  is a front view of the improved euthanasia apparatus of the present invention, with the cart/cage combination properly positioned therein. 
           [0016]      FIG. 2A  is a view of the front wall of the improved euthanasia apparatus of  FIG. 2 , showing interior details. 
           [0017]      FIG. 3  is a side view of the improved euthanasia apparatus of  FIG. 2 . 
           [0018]      FIG. 3A  is a side view of the improved euthanasia apparatus of  FIG. 2 , showing interior details. 
           [0019]      FIG. 4  is a rear view of the improved euthanasia apparatus of  FIG. 2 , showing the cart/cage combination therein. 
           [0020]      FIG. 4A  is a rear view of improved euthanasia apparatus of  FIG. 2 , showing interior details. 
           [0021]      FIG. 5  is a top view of the improved euthanasia apparatus of  FIG. 2 . 
           [0022]      FIG. 5A  is a top view of the improved euthanasia apparatus of  FIG. 2 , showing interior details. 
           [0023]      FIG. 5B  is an enlarged detail view of the door and threshold of  FIG. 5A . 
           [0024]      FIG. 5C  is a section cut through the door bottom showing the inflatable seal therein. 
           [0025]      FIG. 5D  is a perspective view of one embodiment of a seal, usable around the periphery of the chamber opening. 
           [0026]      FIG. 5E  is an enlarged detail view of the fresh air inlet and damper of  FIG. 5A . 
           [0027]      FIG. 6A  is the front view of  FIG. 2  shown enlarged. 
           [0028]      FIG. 6B  is the side view of  FIG. 3  shown enlarged. 
           [0029]      FIG. 7A  is a front view of a cart/cage combination that is usable with the improved euthanasia apparatus of  FIG. 2 , 
           [0030]      FIG. 7B  is a first side view of the cart/cage combination of  FIG. 7A . 
           [0031]      FIG. 7C  is a rear view of the cart/cage combination of  FIG. 7A . 
           [0032]      FIG. 7D  is a second side view of the cart/cage combination of  FIG. 7A , 
           [0033]      FIG. 7E  is a top view of the cart/cage combination of  FIG. 7A . 
           [0034]      FIG. 8  is an enlarged front view of the electrical panel of the improved euthanasia apparatus of  FIG. 2 , 
           [0035]      FIG. 9  is a side view of the electrical panel of  FIG. 8 . 
           [0036]      FIG. 10  is an enlarged detail view of the indicator lights and switches on the electrical panel of  FIG. 8 . 
           [0037]      FIG. 11  is a rear view of the electrical panel of  FIG. 8 . 
           [0038]      FIG. 12A  is a first screen shot of the display from the touch screen of the human machine interface in the electrical panel of  FIG. 8 . 
           [0039]      FIG. 12B  is a second screen shot of the display from the touch screen of the human machine interface in the electrical panel of  FIG. 8 . 
           [0040]      FIG. 12C  is a third screen shot of the display from the touch screen of the human machine interface in the electrical panel of  FIG. 8 . 
           [0041]      FIG. 12D  is a fourth screen shot of the display from the touch screen of the human machine interface in the electrical panel of  FIG. 8 . 
           [0042]      FIG. 13  shows a front view of an alternate embodiment of the improved euthanasia apparatus of the present invention, shown with the cage removed from the chamber. 
           [0043]      FIG. 14  is a side view of the improved euthanasia apparatus of  FIG. 13 . 
           [0044]      FIG. 15  is a rear view of the improved euthanasia apparatus of  FIG. 13 . 
           [0045]      FIG. 16  is a top view of the improved euthanasia apparatus of  FIG. 13 . 
           [0046]      FIG. 17  is a side view of a third embodiment of the improved euthanasia apparatus of the present invention, shown with the door closed. 
           [0047]      FIG. 18  is a rear view of the improved euthanasia apparatus of  FIG. 17 . 
           [0048]      FIG. 19  is a pneumatic schematic for the inflatable seal of the door of the present invention. 
           [0049]      FIG. 20  is a first electrical schematic including the air exhaust fan and the CO2 exhaust fan. 
           [0050]      FIG. 21  is a second electrical schematic including the power supply and the HMI (PanelView plus) device. 
           [0051]      FIG. 22  is a third electrical schematic including the electro-magnetic door lock. 
           [0052]      FIG. 23  is a fourth electrical schematic including the electro-magnetic door lock. 
           [0053]      FIG. 24  is a fifth electrical schematic including the electro-magnetic door lock. 
           [0054]      FIG. 25  is a sixth electrical schematic including the CO2 flow meter, pressure and concentration sensors, 
           [0055]      FIG. 26  is a seventh electrical schematic including an emergency stop device. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0056]      FIG. 1  shows a piping and instrumentation diagram for the improved animal euthanasia apparatus  10  of the current invention, while  FIGS. 2-5  show orthogonal views of the device. As seen in  FIG. 2  and in the enlarged view of  FIG. 6 , the device may preferably be constructed of sufficient dimensions to accommodate euthanizing of a single large animal—perhaps one being as large as, or even larger than a man, and may thus also accommodate simultaneous euthanizing of many smaller animals. Scaling of the invention to be larger or smaller is readily accomplished, as seen in the following discussion. 
         [0057]    The improved animal euthanasia apparatus  10  may include a chamber  20 . The chamber  20  may be formed in one of several different ways. The chamber may be formed of a plastic material that may be compatible with the euthanizing gas that is to be inhaled by the animals. For example, where the euthanizing gas is carbon dioxide (CO2), material compatibility is found with such plastics as: Kel-F type Neoflon M 400H, polychlorotrifluorethyene (PCTFE); Polytetrafluoroethylene (PTFE) such as the brand by DuPont Co. known as Teflon; ethylene-tetrafluoroethylene modified copolymer (ETFE) which is often referred to by DuPont&#39;s trade name Tefzel®; and KYNAR. It may thus be possible to form the chamber into any desired shape, including an irregular shape. As it may be useful to load animal cages therein, which is discussed hereinafter, the chamber may be more efficient when formed to be generally box-shaped, and may thus be a six-sided or faceted enclosure. This form of enclosure for the chamber  20  may therefore be a single continuous wall member with contouring between the faceted sides. 
         [0058]    Many metallic materials are also compatible with CO2 and other euthanizing gases, such as copper, zinc, aluminum, brass, monel, and stainless steel. Therefore, the chamber  20  may also be built using one of these metallic materials, which may lend itself to being formed using discreetly different numbers of wall sections. For example, a first continuous wall section may be formed with four sides, with the ends being mechanically joined together, and a second continuous wall section may be similarly formed, with the pair of four sided wall sections being nested together and mechanically joined using suitable fasteners to form a box. Alternatively, rather than using combinations of multiple-faceted wall sections, individual walls may be separately formed and joined to form a cavity in chamber  20 , including, as seen in  FIG. 2 , a front wall  21 , a first side wall  22 , a rear wall  23 , a second side wall  24 , a floor  25 , and a roof wall  26 . Any suitable stiffener arrangement may be utilized to support the walls, which may be formed of sheet metal, and which may, for strength and other considerations, be formed using a suitable austenitic stainless steel. Each of the mechanically fastened joints may be further sealed to prevent leakage of the gas therethrough. These seams may each be caulked with a caulking material, including, but not limited to, silicone. 
         [0059]    The first side wall  22  may include an opening having a periphery  22 P ( FIG. 3 ), which may be sealed by a door  50 . The door  50  may be mounted to the first side wall  22  through the use of one or more hinges  51 , to enable it to be pivotable with respect to the chamber  20 , and movable between an open position ( FIG. 5 ) and a closed position ( FIG. 2 ). The chamber floor  25  may transition at the opening periphery  22 P into a threshold  25 T, which may be configured to permit the wheel or wheels of a cart to roll from the adjacent floor area  5  across threshold  25 T, to thereby enter the interior of chamber  20 . This arrangement permits the operators of the improved animal euthanasia apparatus  10  to utilize a wheeled cart/cage combination  100  for convenient placement of the animals to be euthanized within the device. One example of such a cage/cart combination  100  is shown within  FIGS. 7A-7E . The cage/cart combination  100  may utilize a single wheel being rotatably mounted to a bottom of the cart, which may be lifted by the operator and steered in through the opening of the chamber, much like a wheelbarrow, and which may be assisted by the cage rail guides  28 A and  28 B that may be secured to the interior of the front and rear walls  21 / 23  of the chamber, as seen in  FIG. 17 . Alternatively, the cage/cart combination  100  may utilize four wheels  101 , which may be swivel casters to easily allow for its manipulation into and out from the chamber  20 . The cage/cart combination  100  may have a frame  102 , around which one or more cages may be integrally built/assembled. For example, the cage/cart combination  100  in  FIGS. 7A-7E  is specifically constructed to house and raise birds, after which they will be terminated, and so the cage/cart combination is specifically designed to work together with the improved animal euthanasia apparatus  10 . The cage/cart combination  100  may be partitioned into six separate cages ( 103 A- 103 F), each of which may have a separate opening with a corresponding cage access door, a separate water cup with leveler valve  104 , and an open space below the cage to receive a tray usable for the collection of feces that may be routinely analyzed. Rather than having cages integrally constructed with the cart, separately assembled cages may simply be placed on shelves of the cart, or they may be stacked upon each other. Note that in one embodiment of the cage/cart combination  100 , its construction may be such that the bottom-most cage(s) may be positioned above the ground floor area  5  at a height being sufficient to avoid being quickly engulfed by the euthanizing gas, prior to the animal therein being permitted to be rendered unconscious, which is discussed hereinafter. 
         [0060]    In an alternate embodiment of the invention, a second door  50 ′ may be similarly installed upon wall  24  to seal an opening therein, with its inflatable seal sealing against a second threshold. With this arrangement, as may be understood from the top view of  FIG. 5 , the process may be better adapted for processing of large numbers of animals housing in different cart/cage combinations, whereby a first cart/cage may be wheeled in one door of the apparatus, both doors may be closed and sealed, and the euthanasia process conducted, and then the first cart/cage with carcasses therein may be wheeled out the second door, while another cart/cage is loaded into the chamber  20 ′ through the first door. This also makes for easier maneuvering of the cart/cage, as the casters do not need to be jockeyed to reverse the direction of movement of the cart/cage combination currently in the chamber  20  to accomplish its removal therefrom. 
         [0061]    A manually operated door handle/latch  55  may be used so that the door may remain secured across and/or within the opening—in the closed position—during the procedure. The latch may be a push-to-close, door face-mount latch with an emergency release handle, which is available online from McMaster-Carr. An electro-magnetic lock  56  ( FIG. 6B ) may furthermore be used in addition to the latch  55 , to protect against inadvertent opening of the door  50  when the chamber  20  is being utilized for euthanizing of animals with toxic gas. Lock  56  may be one of the M400 high security series of electro-magnetic locks made by Schlage®. 
         [0062]    Secured to the first side wall  22 , around the opening periphery  22 P, may be a seal  53 . The seal  53  may be one continuous seal member that may begin on one side of the opening periphery  22 P proximate to the threshold, and may span across the top of the opening, and may run down the other side of the opening periphery to terminate at a position that is also proximate to the threshold (see  FIG. 5B ). Seal  53  may be a push-on type edge seal member, such as the one shown in  FIG. 5D , which may be manufactured from buna-N rubber, and which is available from McMaster-Carr, in Los Angeles, Calif. Alternatively, the seal may be a plain elastomeric seal that is received in a groove on the face of the wall, or it may be any other suitable seal type/arrangement known in the art. When the door  50  is closed and secured using latch  55 , it may engage the seal  53  to seal the chamber, except at the threshold  25 T, which, being configured to accommodate the rolling of a wheeled cart/cage combination thereon, is not adapted for such sealing. Therefore, door  50  is particularly configured to include an inflatable seal on the bottom of the door. 
         [0063]      FIG. 5C  shows a cross-sectional view through the bottom of the door  50 . Inflatable seal  54  may be configured to seal the door  50  with respect to the threshold  25 T, and with respect to the two ends of the door edge seal  53 , where its ends terminate proximate to the threshold, to thereby generally seal the chamber, when the door is closed and latched, against unintended fluid communication with the surrounding environment. Inflatable seal  54  may be supported within a seal housing  54 H, and may be in fluid communication with a valve and a pump, to thereby permit selective inflation/deflation of the inflatable seal during the process of euthanizing the animals. The pump may also be used to power pneumatic actuators used on the apparatus. Instead of an integral pump and valve, the inflatable seal may be in fluid communication with a port that may be coupled to a source of compressed air that is located at the facility that will utilize the apparatus  10 . The inflatable seal may be made of a number of different materials, including, but not limited to, silicone. A door brush  52  may be secured to the bottom of the door  50  at its back edge, as seen in  FIG. 5B , and may include a series of bristles that may sweep the threshold to be clear of any dirt or debris that could hinder the integrity of the sealing thereon by the inflatable seal  54 . 
         [0064]    To enable functioning of the improved animal euthanasia apparatus  10  of the current invention, the chamber  20  may have a series of ports that are particularly configured for fluid transfer in to or out from the chamber, which is generally illustrated within the piping and instrumentation diagram of  FIG. 1 . The chamber  20  may include a euthanizing gas supply valve in one of the walls, or instead, the chamber may have a pipe that is in fluid communication therewith, where the pipe has a supply valve to control the flow of euthanizing gas into the chamber. The pipe may connect to a supply of euthanizing gas, such as the tank  60  of CO2 seen in  FIG. 1 , which may have its own shut-off valve  61  thereon to control flow of the gas therefrom. The supply valve  63  may be a pilot operated solenoid valve, which may be obtained from Asco Valve, Inc., in Florham Park, N.J. (e.g., ASCO Red Hat 2/2 series 8210). A heater may be used to heat the flow from the tank, to ensure that a gas is introduced, and not a liquid or a liquid with ice having formed therein, and to furthermore introduce the gas at a temperature set point sufficient to prevent discomfort to the animals. The supply of euthanizing gas from the chamber supply valve  63  may be distributed within the chamber  20  using a manifold  70 , as seen in  FIG. 3A , and/or by using an upper circulation fan  651 J or a floor fan  65 L, as seen in  FIG. 15 . The manifold  70  may include, as seen in  FIGS. 15 and 18 , a pressure transducer  71 , a solenoid valve  72 , a mass flow meter  73 , a high purity gas regulator  74 , and an on/off ball valve  75 . The ball valve may serve as a manual override with lock out capability for the gas flow. The high purity regulator may control the incoming pressure of the CO2, while the solenoid may just turn the delivery on and off. 
         [0065]    Admission of euthanizing gas into the sealed chamber  20  to occur without a corresponding pressure increase—an effect that might unnecessarily cause discomfort to the animals within the chamber—requires a port that is adapted for accomplishing removal of the fresh air therein. As seen in  FIGS. 3 and 5 , the improved animal euthanasia apparatus  10  may include a fresh air exhaust fan and damper  66 , which may be positioned on an upper part of the rear wall  23  of chamber  20 , or which may be positioned elsewhere, including the roof  26  of the apparatus. The damper may be used to open and to close the port to correspondingly permit or prevent fresh air flow through the opening, and the fan may accelerate the removal of fresh air when the fresh air exhaust damper is opened. The introduction of euthanizing gas through the chamber supply valve  63  and the expulsion of the fresh air using the fresh air exhaust fan and damper  66  may be coordinated during the process. (Note—a pressure relief valve  79  may also be incorporated into one of the walls of the chamber  20 , as seen in  FIG. 18 ). 
         [0066]    After the animals have been successfully euthanized, which is discussed further hereinafter, the lethal gas contained within the chamber  20  must be properly expelled before the operator of the device may open the door to be able to safely proceed with the removal of the cage/cart combination and the carcasses therein. To accomplish expulsion of the CO2 or other noxious gas, the chamber  20  may include one or more openings that may each receive an exhaust gas fan and damper combination  67 , which may be positioned on a lower part of the chamber wall ( FIG. 3 ). The exhaust openings may be interconnected within the interior of the chamber using an exhaust duct  67 D, which may have a replaceable exhaust filter  67 F therein, for filtering the air that is removed from the chamber  20  (e.g.,  FIG. 3A ). 
         [0067]    To avoid creating a vacuum within the sealed chamber during the evacuation of the CO2, the chamber may also include one or more fresh air inlet openings and corresponding dampers  68 . The damper(s) may be manually opened and closed. Alternatively, any of the dampers disclosed herein may be mechanically actuated, where a hydraulic or pneumatic actuator may be configured to open and close a damper door. Instead of the hydraulic or pneumatic actuator, an electro-mechanical solenoid  68 A may be used to actuate the damper, as seen in  FIG. 5E . The interior side of the damper may include a replaceable filter  68 F, which may also be seen in  FIG. 2A . Each of the fresh air inlet openings and corresponding dampers  68  may have a corresponding fan to assist in the admission of fresh air through the opening(s)—air which may otherwise be drawn into the chamber as a result of the evacuation of the euthanizing gas by the exhaust gas fan. These fresh air fan(s) may also be manually turned on and off, or may be signaled to turn on/off as part of an automated euthanasia process. The exhausting of euthanizing gas using the exhaust gas fan and damper combination  67 , and the opening of the damper(s) for the fresh air inlet openings may be coordinated during the process to preclude creating a vacuum, which may cause an excessive load on the exhaust gas fans. The exhaust gas may preferably be ducted to the exterior of the facility or to a holding tank. 
         [0068]    The improved animal euthanasia apparatus  10  of the current invention may include an electrical panel  40 , which appears in the main views of the apparatus, and is shown enlarged in the details views of  FIGS. 8-11 . The electrical panel  40  may receive power from a power supply, which may be a single phase, 120 VAC, 60 Hz, 20 Amp service. The electrical panel  40  may be electrically coupled to each of the electrical components herein to supply power thereto, and to be able to control timely switching of those components on and off, as part of an automated process. Powering on and off of the unit may be controlled by a selector switch  42  configured to receive a key to control the availability of power to the device from the main electrical source ( FIG. 10 ). To accomplish automation of the euthanasia process by the apparatus, a digital computer utilizing one or more processors or microprocessors may be utilized. A programmable logic controller (PLC) may also be utilized, such as the MicroLogixe  1400  by Allen Bradley  38  ( FIG. 11 ), which may be used in combination with a human machine interface (HMI), such as the Allen Bradley PanelView Plus touch screen  35 . The touch screen  35  may be used for monitoring conditions in the chamber  20  and to receive notification of any alarms (flow rates, line pressure of the euthanizing gas, chamber oxygen levels, etc.), and may also be used by the operator to program “set points” for a process, such as the time allotted for the gas to achieve a narcotic effect to render the animals unconscious, which may vary for different species of animals; the time of exposure by the animals to the lethal dose of gas necessary to assure euthanizing of the particular species; setting of the CO2 and/or Oxygen levels/concentrations; etc (see  FIGS. 12A-12D ). 
         [0069]    Automation of the process may be more readily and safely accomplished through the incorporation of several other component parts into the improved animal euthanasia apparatus  10 . An indicator light  43  may be used to detect when the door has been closed and locked by the electro-magnetic lock  56 , after which the light may illuminate with a yellow color. A three-color beacon (green, amber, red) with an audible alarm  36  may extend away from the electrical panel  40  and may signal different stages of the process, as discussed hereinafter. 
         [0070]    A cage in-place whisker switch may be used to confirm proper positioning of the cart/cage  100  within the chamber  20 , where such detection of the cart/cage combination  100  by the switch may trigger a cage in-place light  44  on the electrical panel  40  to illuminate with a green color. A stop may be used to limit further travel of the cart/cage  100  into the interior cavity of chamber  20 , after it has been properly positioned therein, as indicated by contact with the whisker switch. 
         [0071]    The electrical panel  40  may also include a “cycle start” push button  45 , which may illuminate with a green color after it has been depressed to begin the process, and which may be accompanied by an audible alarm that may beep one or more times at the start of the process. A “cycle stop” button  46  may be provided to prematurely stop the process prior to its automated completion. The “cycle stop” button  46  may illuminate with a red color once it has been depressed. Actuation of the emergency release handle  55 E of latch  55  on the interior of the chamber  20  ( FIG. 14 ) may similarly cause interruption of the normal cycle, in an “E-stop condition,” which may cause unlocking of the electro-magnetic door lock  56 , and advancing of the procedure to the “Fresh Air Introduction Cycle,” where any further introduction of euthanizing gas (e.g., CO2) is stopped, the fresh air inlet dampers may be opened, and the exhaust gas fan and damper combination  67  may be activated. When the automated euthanasia process has proceeded normally to its completion, a “cycle complete” light  47  may illuminate with a green color. 
         [0072]    The improved animal euthanasia apparatus  10  of the current invention may include a number of different alarms that may cause an alarm light  49  to be illuminated with a red color. For example, if an operator was trapped in the chamber and the start of the euthanizing process was accidentally initiated, the operator may simply trigger the E-stop condition,” by actuating the emergency release handle of latch  55 , which would set off the alarm. If the door fails to properly latch/lock, resulting in a door open fault, the alarm may be triggered. If the inflatable seal on the door experiences any loss in seal pressure (i.e., pump failure resulting in loss of pressure being exerted by the seal, or failure of the seal or of its connections), this will trigger the alarm. If any of the fans become overloaded, as mentioned previously, the alarm will be triggered. If there is a component failure, and the euthanizing gas is introduced outside of a programmed set point (e.g., a time set point is exceeded, a low gas flow is occurring, a high flow fault occurs, a low pressure condition occurs, or a high pressure condition occurs, etc.), the alarm may sound. To recover from an alarm, the reset button  48  may be depressed. As a safety precaution, the reset button  48  may be programmed to require entry of a password, in order to continue the process, once the erred condition has been resolved. 
         [0073]    The improved animal euthanasia apparatus  10  of the current invention may also include a translucent observation window  21 W in the front wall  21 , which may be sealed against leakage with respect to the wall using any suitable seal, including a gasket seal. A wash-down rated fluorescent light may be used to illuminate the interior of the chamber for the operator to observe the animals therein. Merely to be exemplary, where the dimensions of the apparatus  10  are constructed to be approximately 84 inches high, by 79 inches wide, by 89 inches long, which may accommodate the cage/cart combination  100  of  FIGS. 7A-7E  being 24″×64″×70,″ the fluorescent light may be 48 inches long to provide sufficient illumination throughout the interior of the chamber. An upper portion of the apparatus  10  may be configured to receive one or more eye bolts ( FIG. 17-18 ) or other means of lifting  77  of the device, for its transport within a facility, or for delivery to a recipient of the device. 
         [0074]    Operation of the improved animal euthanasia apparatus  10  may generally be as follows. The operator may insert the key into the keyed power selector switch  42 , and turn on power to the unit. The HMI  35  will illuminate indicating there is power to the unit. The “AIR ON” light  41  or “Air OK” window (on HMI screen) will illuminate green indicating there is compressed air to the machine. The chamber fluorescent light  78  and air circulation fan(s)  65  will turn on. The Block Heater/Vaporizer will power up. The operator may next open the CO2 supply valve  61  on the liquid CO2 tank  60 , and may unlock and open the manual CO2 supply valve to the Chamber, A beacon and the alarm light  49  will be illuminated Red. The reset pushbutton  48  may be pressed after a short delay, after which the alarm light and beacon will no longer be illuminated. 
         [0075]    The operator may next use the door handle/latch  55  to open the door  50  of the euthanasia chamber  20 , and using the cage rail guides  28 A and  28 B inside the chamber, may load the cart/cage  100  therein until it is resting against the stop at the far end of the cage. The whisker switch will thus be contacted, and the “cage in place” indicator light  44  will be illuminated green. The door  50  may next be closed, and the door latch  55  will engage the door, holding the chamber door shut. The “READY” indicator light  43  and beacon  36  will illuminate yellow. 
         [0076]    The “cycle start” push button  45  may be pressed. The “cycle start” pushbutton and beacon  36  will illuminate (green) and the audible alarm will beep once indicating the apparatus is in operation. The electro-magnetic door lock  56  will engage, preventing accidental opening of the chamber door  50  during the cycle. The inflatable seal  54  will inflate, sealing the bottom of the door  50 , and the CO2 gas introduction cycle will begin. The fresh air inlet dampers  68  will be closed, and the CO2 exhaust fan/damper  67  will be off/closed. The fresh air exhaust damper  66  will open and the CO2 supply valve  63  will open. CO2 will begin to flow into the chamber  20 . The HMI  35  will display the flow rate and line pressure of the CO2 being supplied into the chamber  20 . Oxygen sensor(s)  76  in the chamber  20  will monitor the condition of the atmosphere in the chamber. When the Chamber atmosphere reaches set-point, the Chamber CO2 supply valve  63  will close, and the fresh air exhaust damper  66  will close. The O2 sensor(s) will continue to monitor the condition of the atmosphere in the chamber during the idle/holding phase of the cycle. The fresh air exhaust damper  66  and CO2 supply valve  63  may open/close if required, to maintain atmosphere set-point (CO2 concentration and atmospheric pressure), within a tolerance, over the duration of the idle/holding phase (time set-point) of the cycle. The O2 Monitor, CO2 Flow Meter, and CO2 Pressure sensor will respond accordingly. 
         [0077]    After the idle/holding (time set-point) cycle is complete, the apparatus will begin the “Fresh Air Introduction Cycle.” The CO2 supply valve  63  and fresh air exhaust fan/damper  66  will close and remain closed. The CO2 exhaust fan/damper  67  will be turned on/opened. This will be followed by the fresh air inlet damper(s)  68  opening. The O2 sensors will monitor the condition of the atmosphere in the chamber. When the Chamber atmosphere reaches set-point (safe-level), the CO2 exhaust fan  67  will turn OFF. The inflatable seal  54  will deflate, the electro-magnetic door lock  56  will disengage, and the cycle complete indicator light  47  will illuminate green. The audible alarm will beep ( 2  short beeps) and the beacon  36  will “blink” green indicating the current cycle is complete. The operator may unlatch and open the chamber door  50  and remove the cart/cage  100  from the chamber. Contact with the whisker switch will no longer be made, and the cage in place and cycle complete indicator lights,  44  and  47 , as well as the beacon light  36  will go out. 
         [0078]    Note that during the idle phase, where the animals are being exposed to CO2 within the chamber  20  and the inflatable seal  54  is being maintained in the inflated condition to prevent leakage of the CO2 from the chamber  20 , the pressure within the chamber may be maintained at just slightly below the current atmospheric pressure in the facility where the apparatus is being operated. This would not be noticeable to the animals, but would serve to prevent adverse effects of a pressure differential, whereby higher pressure within the interior of the chamber could tend to counter the effectiveness of the inflatable seal, and could lead to small amounts of leakage of CO2, particularly where the inflatable seal meets the door edge seal. 
         [0079]    It is fairly common to use CO2 for euthanizing of the animals in a process for which guidelines have been suggested by various agencies (see e.g.: “The AVMA Guidelines on Euthanasia”; and “Guidelines for the Use of Carbon Dioxide (CO2) for Rodent Euthanasia,” by the University of Texas at Austin). Since the guidelines suggest that sudden exposure to high concentrations of CO2 can cause distress to the animals, and that unconsciousness should first be induced, the rate of introduction of the CO2 can be controlled in several different ways. 
         [0080]    In a first alternate embodiment, the CO2 gas may be introduced at a suggested rate that is very slow, and would displace the air in the cage at a rate of 20% by volume, per minute. During this time the circulation fan  65  may be used to cause mixing of the CO2 and air. As the concentration of CO2 reaches 40% to 50%, unconsciousness would occur in most species of animals, which may be verified visually through the observation window  21 W. The CO2 concentration could subsequently be increased to lethal levels and held thereat for the prescribed time period. 
         [0081]    In another alternate embodiment of the procedure, at least two oxygen sensors  76  may be mounted in the chamber  20 , at distinctly different heights. CO2 is denser than air, and thus tends to sink to the bottom of the chamber  20 , when introduced therein, and thus accounts for the relative positioning in the chamber  20  of the fresh air exhaust damper  66 , the CO2 exhaust fan/damper  67 , and the fresh air inlet damper  68 . Therefore, a first oxygen sensor may be mounted at a height that would correspond to the chamber being filled with CO2 to a volume that, when mixed with the remaining air, would create a narcosis inducing concentration of the CO2-air mixture for the particular species of animal (i.e., 40-50%). After filling the chamber to that level, the CO2 introduction process may be temporarily ceased, and the circulation fan  65  may be used for such mixing. After unconsciousness has been observed in the animals, the CO2 introduction process may again proceed, until the level of CO2 has risen to the reach an O2 sensor that is mounted at an elevated height in the chamber  20 , which would result in substantially a 100% concentration of the euthanizing gas therein. Different concentration levels of euthanizing gas for inducing unconsciousness in different species of animals may be programmed into the PLC  38 , and additional oxygen sensors may be utilized to sense the required height for the initial introduction of gas for anesthetization therein, for the particular species, using various different inhalants. As noted earlier, in regard to the construction of cart/cage  100 , this alternate embodiment of filling the chamber with gas may necessitate that the lowest most cage situated within the chamber be at a level that would be above the lower oxygen sensor, to avoid suddenly immersing the lowermost animals therein to the inflowing CO2, prior to reaching the 40% level and the start of the mixing stage. 
         [0082]    The examples and descriptions provided merely illustrate a preferred embodiment of the present invention, Those skilled in the art and having the benefit of the present disclosure will appreciate that further embodiments may be implemented with various changes within the scope of the present invention. Other modifications, substitutions, omissions and changes may be made in the design, size, materials used or proportions, operating conditions, assembly sequence, or arrangement or positioning of elements and members of the preferred embodiment without departing from the spirit of this invention.