Abstract:
An apparatus for supplying a precise oxygen-nitrogen gas mixture to an animal comprises (i) A source of pressurized oxygen gas, (ii) A source of pressurized nitrogen gas, (iii) A mechanical two-gas blending valve having a first and second gas inlet couplings, and an outlet coupling, the gas blending valve having a manual selector that can incrementally adjust the oxygen-nitrogen gas mixture within a range of mixtures, and a face plate on the blending valve including markings adjacent to the manual selector that are indicative of specific oxygen-nitrogen mixtures, wherein the gas inlets are coupled to the sources of oxygen and nitrogen, respectively, (iv) A gas dispenser coupled to the outlet of the mechanical two gas blending valve; and (v) An animal interface coupling to deliver the gas mixture to the subject animal. The apparatus may be provided for mixtures of air and any gas of interest.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims the benefit of Provisional Patent Applications Ser. No. 60/940,552 filed May 29, 2007 entitled “Method and Apparatus for Simplified Precise Mechanical Gas Mixing and Delivery for Animal Research.” 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a method and apparatus for precision gas mixing and delivery for animal research, more particularly, the present invention provides a method and apparatus for precise oxygen/nitrogen and other gas mixing and delivery for animal studies. 
         [0004]    2. Background Information 
         [0005]    In animal studies, such as hypoxia studies, the mixing of respiratory gases to be delivered to the subjects is an arduous setup for the study. One common approach is to develop a precise mixing valve arrangement with metered flow valves leading to a blending “T”, whereby the researchers calculate the desired flow rates for the specific constituents to obtain the desired gas mixture. In addition to the time consuming issue, calculation errors can lead to an invalidation of the study results. 
         [0006]    Another common approach is to limit the studies to pre-packaged mixtures that are supplied by others (e.g. Compressed Air, 18% O2/82% N, 15% O2/85% N, etc). This approach simplifies the gas mixing step but limits the data points that are available and is simply unacceptable for many studies. 
         [0007]    Researchers P. A. Robbins, G. D. Swanson, A. J. Micco and W. P. Schubert developed a “fast gas-mixing system for breath-to-breath respiratory control studies” described in Journal of Applied Physiology, Vol 52, Issue 5 1358-1362, 1982. This is a computer-controlled gas-mixing system that manipulates inspired CO2 and O2 on a breath-to-breath basis, wherein the system uses pairs of solenoid valves, one pair for each gas. The valves cycle open and shut every 1/12 s. A circuit converts signals from the computer, which dictates the flows of the gases, into a special form for driving the valve pairs. These signals determine the percentage of time within the 1/12-s cycle each valve spends in an open state and the percentage of time it spends shut, which, in effect, sets the average flows of the various gases to the mixing chamber. The delay for response of the system to commanded CO2 or O2 changes is less than 200 ms. 
         [0008]    CWE Inc. has developed the GSM-3 Gas Mixer for creating custom respiratory gas mixtures. Any three gases can be connected as inputs, and the output is the user-programmed mixture of these gases. The instrument can operate in a stand-alone mode, with mixture programming done from the front panel controls, or it can be controlled using an attached computer running the supplied software. The mixer uses thermal mass flow controllers to provide any programmed mixture in the range of 0-10 lpm for each gas with a resolution of 0.1% concentration. Front panel controls are used to set the desired total output flow, as well as the concentration of each of the three component gases. The LCD display shows the set concentrations, as well as the computed flow rates for each gas. Up to four custom mixtures can be created and stored in non-volatile memory for future use. Any of these stored mixtures can be immediately selected and executed. This function allows rapid step-changes in concentrations to be performed with the push of a button. The flow controllers are pre-calibrated for the three most commonly used respiratory gases: O2, CO2, and N2. Other gases can also be selected, and internal correction factors are automatically applied to compensate the flow controllers for differing gas densities. The GSM-3 Gas Mixer comes ready to use with CDROM software and a serial cable. 
         [0009]    These computerized, digital gas mixing devices still represent several problems for the researchers. The first is that these systems can be priced beyond the researcher&#39;s budget for particular studies and may not be useful in that they are (due to costs constraints) not made readily available to the researchers. Secondly they add too much complexity to the gas mixing procedure, although they do provide for accuracy (assuming the researchers do not hook the systems up incorrectly). 
         [0010]    There remains a need in the art for a simple-to-operate, intuitive, accurate, precise gas mixing method and apparatus for animal studies. 
       SUMMARY OF THE INVENTION 
       [0011]    One embodiment of the present invention provides an efficient apparatus for supplying a precise oxygen-nitrogen gas mixture to an animal comprises (i) A source of pressurized oxygen gas, (ii) A source of pressurized nitrogen gas, (iii) Regulators on each gas source to regulate the pressure of each gas, (iv) A mechanical two gas blending valve having a first gas inlet coupling, a second distinct gas inlet coupling and an outlet coupling configured for dispensing an oxygen-nitrogen mixture, the gas blending valve having a manual selector that can incrementally adjust the oxygen-nitrogen gas mixture within a range of mixtures, and a face plate on the blending valve including markings adjacent to the manual selector that are indicative of specific oxygen-nitrogen mixtures, or given percentages of either or both gases, wherein the gas inlets are coupled to the sources of oxygen and nitrogen, respectively, (v) A gas dispenser coupled to the outlet of the mechanical two-gas blending valve; and (vi) An animal housing configured to contain an animal therein, wherein the gas dispenser is coupled to the animal housing and configured to dispense the oxygen-nitrogen gas mixture to the animal housing, or any interface coupling to deliver the gas mixture to the airway of the subject directly, or through another device such as a mechanical ventilator 
         [0012]    The present invention further includes a method comprising the additional steps of coupling the source of oxygen gas to a gas inlet of the blending valve; coupling the source of nitrogen to a gas inlet of the blending valve; Manually adjusting the selector to select a given oxygen-nitrogen gas mixture; and simultaneously supplying oxygen gas to the blending valve, whereby the blending valve will dispense the oxygen-nitrogen mixture to the dispenser that will dispense the oxygen-nitrogen mixture to the animal within the animal housing, or to any other airway interface. 
         [0013]    In some non-limiting embodiments of the present invention the first gas inlet coupling is coupled only to the source of oxygen and the second gas inlet coupling is coupled only to the source of nitrogen. One non-limiting aspect of this embodiment provides that the source of oxygen is a compressed oxygen container and the source of nitrogen is a compressed nitrogen container wherein the face plate includes markings adjacent the manual selector that are indicative of specific oxygen-nitrogen mixtures from 0% oxygen to 100% oxygen. Another non-limiting aspect of this embodiment provides that the source of oxygen is a compressed air container and the source of nitrogen is a compressed nitrogen container and wherein the face plate includes markings adjacent the manual selector that are indicative of specific oxygen-nitrogen mixtures from 0% oxygen to 21% oxygen. 
         [0014]    In some non-limiting embodiments of the present invention further include three containers including a compressed air container, a compressed nitrogen container and a compressed oxygen container, wherein two of the three containers are selectively coupled to the blending valve to provide the source of oxygen and the source of nitrogen to the blending valve, whereby an oxygen-nitrogen selection provides for a gas mixture range of 0% Oxygen to 100% Oxygen on the manual selector, an air-nitrogen selection provides for a gas mixture range of 21% oxygen to 0% Oxygen, and an Air-Oxygen selection provides for a gas mixture range of 21% Oxygen to 100% Oxygen. 
         [0015]    One nonlimiting aspect of the invention provides a method of supplying an air and subject gas of interest gas mixtures between 0% gas of interest and X% gas of interest to an animal, wherein X is less than 100%. This method comprises the steps of: (i) Providing a source of pressurized air; (ii) Providing a source of pressurized gas of interest, wherein the source of gas of interest is a preformed mixture of X% gas of interest and the remainder air; (iii) Providing a mechanical two gas blending valve having a first gas inlet coupling, a second distinct gas inlet coupling and an outlet coupling configured for dispensing an air-gas of interest mixture, the gas blending valve having a manual selector that can incrementally adjust the gas mixture within a range of mixtures, and a face plate on the blending valve including markings adjacent to the manual selector that are indicative of specific air-gas of interest mixtures between 0% and X% gas of interest concentrations; (iv) Providing a gas dispenser coupled to the outlet of the mechanical two gas blending valve; (v) Providing an animal interface coupled to the gas dispenser and configured to deliver the gas mixture to the subject animal; (vi) Coupling the source of air to a gas inlet of the blending valve; (vii) Coupling the source of gas of interest to a gas inlet of the blending valve; (viii) Manually adjusting the selector to select a given gas mixture; (ix) Simultaneously supplying air and gas of interest containing gas to the blending valve, whereby the blending valve will dispense the selected gas mixture to the dispenser that will dispense the gas mixture to the animal through the animal interface. 
         [0016]    These and other advantages of the present invention will be clarified in the brief description of the preferred embodiment taken together with the drawings in which like reference numerals represent like elements throughout. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a schematic view of an oxygen-nitrogen gas mixing apparatus for animal research according to one aspect of the present invention; 
           [0018]      FIG. 2  is a schematic view of an air-nitrogen gas mixing apparatus for animal research according to one aspect of the present invention; 
           [0019]      FIG. 3  is a schematic view of an oxygen-nitrogen-air gas mixing apparatus for animal research according to one aspect of the present invention; and 
           [0020]      FIG. 4  is a schematic view of a multiple gas mixing apparatus for animal research according to one aspect of the present invention; 
           [0021]      FIGS. 5A and 5B  are schematic views of particular face plates for gas mixing apparatuses for animal research according to aspects of the present invention; and 
           [0022]      FIG. 6  is a schematic view of an air/gas-of-interest gas mixing apparatus for animal research according to one aspect of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]      FIG. 1  is a schematic view of an oxygen-nitrogen gas mixing apparatus  10  for animal research according to one aspect of the present invention that will provide specific oxygen-nitrogen mixtures from 0% oxygen to 100% oxygen. 
         [0024]    The apparatus  10  includes a source of pressurized oxygen gas in the form of a compressed oxygen gas container  12 , or canister, that is widely commercially available from gas suppliers. The container  12  should meet the specifications and color markings of an Oxygen tank, as established by the Compressed Gas Association. The container  12  includes an oxygen tank fitting  14 , also called a CGA—oxygen gas fitting. CGA stands for “Compressed Gas Association” which is the group that established standards in the gas industry for fittings which are used to attach to specific gas cylinders. For nearly a century, the Compressed Gas Association has been dedicated to the development and promotion of safety standards and safe practices in the industrial gas industry. CGA fitting standards are developed through the combined efforts of more than 200 member companies worldwide. In general, these CGA fitting connections are designed for metal-to-metal sealing, however a sealing washer may be provided on those fittings that do not have a metal-to-metal set. 
         [0025]    The fitting  14  couples to a regulator assembly  16  associated with the oxygen container  12 . The regulator assembly  16  is equipped with a CGA fitting  18  that matches its intended gas service, namely oxygen gas, and thus matches fitting  14 . The regulator assembly  16  includes a conventional gas regulator  20  for the oxygen gas to regulate the pressure of the outgoing gas. The outlet of the regulator assembly  16  is a CGA fitting  22  that is specific to oxygen. 
         [0026]    A coupling hose with a CGA fitting  24  specific to oxygen is attached to the CGA fitting  22  of the regulator assembly and opposite CGA fitting  26  specific to oxygen is coupled to a CGA fitting  28  specific to oxygen found on a two-gas mechanical blending valve  30 . 
         [0027]    Two gas mechanical blending valves, per se, are known in the medical respiratory fields such as the M2100 Air/O2 Blender from General Electric, Inc. that is designed to blend compressed air and oxygen, and to deliver pressurized gas at precise concentrations. The quality and reliability of Bird® blenders from Viasys Healthcare, Inc. make these two gas mechanical blenders also acceptable for forming the general working structure for the valve  30 . The main modifications needed to these off-the-shelf components is the provision of specific CGA fittings that prevent the researcher from “hooking the system up backwards”, and the calibration of the blender for the oxygen nitrogen mixture from 0% Oxygen to 100% Oxygen as found in the embodiment of  FIG. 1 . 
         [0028]    The apparatus  10  includes a source of pressurized nitrogen gas in the form of a compressed nitrogen gas container  32 , or canister, that is also widely commercially available from gas suppliers. The container  32  should meet the specifications and color markings of a Nitrogen tank, as established by the Compressed Gas Association. The container  32  includes a nitrogen tank fitting  34 , also called a CGA—nitrogen gas fitting. 
         [0029]    The fitting  34  couples to a regulator assembly  36  associated with the nitrogen container  32 . The regulator assembly  36  is equipped with a CGA fitting  38  that matches its intended gas service, i.e. nitrogen, and thus matches fitting  34 . The regulator assembly  36  includes a conventional gas regulator  40  for the nitrogen gas to regulate the pressure of the outgoing gas. The outlet of the regulator assembly  36  is a CGA fitting  42  that is specific to nitrogen. 
         [0030]    A coupling hose with a CGA fitting  44  specific to nitrogen is attached to the CGA fitting  42  of the regulator assembly  36  and opposite CGA fitting  46  specific to nitrogen is coupled to a CGA fitting  48  specific to nitrogen found on a two-gas mechanical blending valve  30 . 
         [0031]    The mechanical two-gas blending valve  30  includes a manually adjustable selector  50  such as a rotary dial with an indicator arm identifying the position. Stops, such as pins, can limit the rotation of the manual selector at the particular extremes. The extreme positions will effectively be at an oxygen-nitrogen mixture of 0% oxygen at one extreme and 100% oxygen at the other extreme, and the intermediate positions will allow the researcher to easily, and precisely select any desired mixture. The face plate  52  of the valve  30  has markings or indicia  54  at specific locations to give the researcher the necessary reference. Only a few indicia points or markings  54  are shown, but as many as desired can be provided to assist the researcher. One particularly useful marking is at 21% oxygen, which is largely the equivalent of Air. One could also mark the faceplate with numbers corresponding to the nitrogen content of the gas rather than the oxygen content, but this would be less useful to an animal researcher given that oxygen is the primary gas of interest.  FIG. 5A  illustrates an appropriate face plate  52  construction including dial  50 . 
         [0032]    The outlet of the valve  30  is a CGA fitting  56 . The fitting  56  is preferably different from inlet fittings  28  and  48  to avoid any miss-assembly by the researcher. A CGA fitting  58  matching fitting  56  is on coupling hose  60  that extends to a gas dispenser  62  that is attached to an animal housing  64  configured to contain an animal therein, wherein the gas dispenser  62  is configured to dispense the oxygen-nitrogen gas mixture to the animal housing  64 . The gas dispenser  62  and animal housing  64  can take a number of forms as known in the art. 
         [0033]    The apparatus  10  allows a researcher to quickly, easily, repeatably and cost-effectively provide any desired Oxygen-Nitrogen mixtures to animals for a variety of studies. The use of specific CGA fittings prevents the researcher from incorrectly assembling the system. The use of the blender valve  30  is intuitive and the markings  54  will give the researcher the precise control needed. Further the CGA components make the system safe for use in research environments. 
         [0034]    The apparatus  10  allows a researcher to perform hypoxia studies on animals, however, in such studies the range of control for the valve  30  is from 21% oxygen to 0% Oxygen with the selector  50 . It is worthwhile to note that hypoxia is an inadequacy in the oxygen reaching the body&#39;s tissues. For these specific studies, the apparatus  110  of  FIG. 2  may be more advantageous. 
         [0035]    The apparatus  110  is similar to apparatus  10  described above wherein like reference numerals represent like elements, and these repeated elements need not be described again. The main difference is that the source of oxygen in this system is from a compressed air container or canister  72 , replacing container  12  of apparatus  10 . 
         [0036]    The container  72  should meet the specifications and color markings of a compressed air tank, as established by the Compressed Gas Association. The container  72  includes an air tank fitting  74 , also called a CGA—air gas fitting. The fitting  74  couples to a regulator assembly  76  associated with the air container  72 . The regulator assembly  76  is equipped with a CGA fitting  78  that matches its intended gas service, i.e. air, and thus matches fitting  74 . The regulator assembly  76  includes a conventional gas regulator  80  for the air gas to regulate the pressure of the outgoing gas. The outlet of the regulator assembly  76  is a CGA fitting  82  that is specific to air. 
         [0037]    A coupling hose with a CGA fitting  84  specific to air is attached to the CGA fitting  82  of the regulator assembly  76  and opposite CGA fitting  86  specific to air is coupled to a CGA fitting  88  specific to air found on the two-gas mechanical blending valve  30 . 
         [0038]    Another important difference with apparatus  110  is that the face place  52  is replaced with another appropriate face plate  92 . The face plate  92  of the valve  30  has markings or indicia  94  at specific locations to give the researcher the necessary reference. Only a few indicia points or markings  94  are shown, but as many as desired can be provided to assist the researcher. The extreme positions will effectively be at an oxygen-nitrogen mixture of 0% oxygen at one extreme and 21% oxygen (i.e. Air) at the other extreme, and the intermediate positions will allow the researcher to easily, and precisely select any desired mixture.  FIG. 5B  illustrates a face plate  92  for the apparatus  110 . The apparatus  110  allows the researcher a greater control of specific settings for ranges of 0-21% Oxygen. 
         [0039]    A further embodiment of the present invention is shown in  FIG. 3  with apparatus  210 . The apparatus  210  combines the advantages of the apparatus  10  and  110  and adds more functionality, at the cost of making the system slightly more complex. The apparatus  210  is similar to apparatus  10  and  110  described above wherein like reference numerals represent like elements, and these repeated elements need not be described again. The main difference is that the apparatus  210  provides for three containers, including the compressed air container  72 , the compressed nitrogen container  32  and the compressed oxygen container  12 , wherein two of the three containers  12 ,  32  and  72  are selectively coupled to the blending valve  30  to provide the source of oxygen and the source of nitrogen to the blending valve  30 . In this apparatus  210  an oxygen-nitrogen selection provides for a gas mixture range of 0% Oxygen to 100% Oxygen on the manual selector  50 , an air-nitrogen selection provides for a gas mixture range of 21% oxygen to 0% Oxygen, and an Air-Oxygen selection provides for a gas mixture range of 21% Oxygen to 100% Oxygen. 
         [0040]    Specifically, the oxygen CGA fitting  28  leads to the inlet of a selector valve  98 , while the nitrogen CGA fitting  48  leads to a T-coupling that is attached to the selector valve  98 , whereby the selector valve can select oxygen or nitrogen to move forward through CGA fitting  100 . The preference for fitting  100  is that it be different from the remaining CGA fittings such that the apparatus only has one way that it can be assembled by the researcher. A coupling hose with a CGA fitting  102  is attached to the matching CGA fitting  100  of the selector valve  98  and opposite CGA fitting  104  is coupled to a matching CGA fitting  106  found on the two-gas mechanical blending valve  30 . Again, preferably the fittings  104  and  106  are selected such that the apparatus is assembled in one correct orientation. 
         [0041]    The air CGA fitting  88  leads to the inlet of a selector valve  108 , while the nitrogen CGA fitting  48  leads to a T-coupling that is attached to the selector valve  98  as noted above and to the selector valve  108  as shown, whereby the selector valve  108  can select air or nitrogen to move forward through CGA fitting  120 . The preference for fitting  120  is that it be different from the remaining CGA fittings such that the apparatus  210  only has one way that it can be assembled by the researcher. A coupling hose with a CGA fitting  122  is attached to the matching CGA fitting  120  of the selector valve  108  and opposite CGA fitting  124  is coupled to a matching CGA fitting  126  found on the two gas mechanical blending valve  30 . Again, preferably the fittings  124  and  126  are selected such that the apparatus is assembled in one correct orientation. 
         [0042]    It should be apparent that the selector valves  98  and  108  allow for the selection of the Oxygen container  12  and the Nitrogen container  32 , or the Oxygen container  12  and the Air container  72 , or the Air container  72  and the Nitrogen container  32 . Technically the valves, as shown, will also allow for a Nitrogen-Nitrogen mixture to be selected, but that is hardly a meaningful combination. Further the face plate  132  includes markings such as  54  and  94 , on different radial bands that are associated with each meaningful combination of gases that can be selected. The apparatus  210  provides obvious additional flexibility to the researcher, but it adds the requirement that the researcher be well aware of the specific selections of the selector valves  98  and  108 . The additional flexibility and increased complexity is reflected in the markings on the faceplate. One possible modification is including sensors on the selector valves  98  and  108  that could be monitored and displayed on the face plate by lighting up the appropriate markings on the face plate  132 , however this type of modification is technically feasible, but difficult to accomplish in a cost-effective manner, and begins to move away from the goals of the present invention. 
         [0043]    Another embodiment of the present invention is to expand upon the flexibility offered with the system of  FIG. 3 .  FIG. 4  illustrates a system that can accommodate any number of gases. The gases could be pre-packaged mixtures of oxygen and nitrogen in addition to air or can be other gases, or mixtures thereof. In this embodiment the selector valves (or three-way valves)  98  and  108  are replaced with two manifolds  160  each having the specific inputs therein, including the Oxygen container  12 , the nitrogen container  32  the air container  72 . Additional gases are reflected with gas container  142  (representing gas n) with CGA coupling  144  leading to regulator assembly  150  with inlet CGA fitting  148 , regulator  150  and outlet CGA fitting  152 . CGA fitting  154  will be coupled to the manifold. As above, it is helpful if the CGA fittings are selected to allow for only one assembly of the apparatus  310 . The manifolds  160  are constructed to select one input gas to move to the gas blender valve  30 . The only remaining difference is that with this many inputs for the valve  30  the face plate  162  will have effectively generic markings  164 . The advantage of the embodiment of apparatus  310  is the added flexibility; however the noted disadvantage is the added complexity to the system and the loss of precise control markings for specific gas mixtures. The researcher must make some basic calculations to determine the Oxygen content (or Nitrogen content, or desired gas presence based upon the inputs) of the resulting mixture. 
         [0044]    A further embodiment of the present invention is to provide an apparatus  510  as shown in  FIG. 6  for providing an air and any subject gas of interest gas mixtures between 0% gas of interest and X% gas of interest to an animal. The apparatus  510  is similar to apparatus  110  described above wherein like reference numerals represent like elements, and these repeated elements need not be described again. The apparatus  510  includes a compressed air container or canister  72 , replacing container  1   2  of apparatus  10 . In this system the remaining canister  512  is a preformed mixture of air and the gas of interest at a concentration of X% gas of interest. The gas of interest may be any gas of interest (e.g. Carbon dioxide, carbon monoxide, methane, etc). The gas of interest and air canister can be made for the researcher by general gas suppliers as the gas supplier need only know the gas of interest and the maximum concentration X of this gas in order to supply the canister  512 . The system will also include a face plate  532  with markings  534  from 0% to X% gas of interest. 
         [0045]    In this embodiment the couplings for the canister  512  are “universal” in that it is expected the system is re-usable for different gases and different maximum concentrations. The container  512  includes a specific tank fitting  544  that couples to a regulator assembly  546  associated with the container  512 . The regulator assembly  546  is equipped with a fitting  548  that matches “universal” fitting  544 . The regulator assembly  546  includes a conventional gas regulator  550  for the nitrogen gas to regulate the pressure of the outgoing gas. The outlet of the regulator assembly  546  is a fitting  552  that attaches to a coupling hose with a fitting  554 . The coupling hose has an opposite fitting  556  coupled to a fitting  558  found on a two-gas mechanical blending valve  30 . The fittings associated with the canister  512  are not specific to a given gas, but should be different from air fittings to prevent the system from being assembled incorrectly. The face plate  532  should be removable or renewable (a stick on face plate  532  supplied by the gas supplier of the canister  512 ). 
         [0046]    The system formed by apparatus  510  is intended to allow a researcher to quickly and easily perform research on gas blends of any relevant gas of interest. As a representative list, the following is a listing of hazardous gases that are detected by solid state sensors (with the levels of detection). This is also not intended to be an exhaustive listing, merely representative. This listing is repeated here as each of the identified “hazardous gases” can be the subject of a number of animal studies. The following listing should also demonstrate that the face plate markings may be in PPM (Parts per Million) of the subject gas, which can be preferred where the ranges of interest are relatively small. 
         [0000]    
       
         
               
               
             
           
               
                   
               
             
             
               
                 Acetic Acid 
                 100, 200 ppm 
               
               
                 Acetone 
                 100, 200, 500, 1000, 5000 ppm; % LEL 
               
               
                 Acetonitrile 
                 100 ppm 
               
               
                 Acetylene 
                 50 ppm; % LEL; 3% by Volume 
               
               
                 Acrolein 
                 50 ppm 
               
               
                 (Acrylaldehyde) 
               
               
                 Acrylic Acid 
                 100 ppm 
               
               
                 Acrylonitrile 
                 50, 60, 80, 100, 200, 500 ppm; % LEL 
               
               
                 Allyl Alcohol 
                 % LEL 
               
               
                 Allyl Chloride 
                 200 ppm 
               
               
                 Ammonia 
                 50, 70, 75, 100, 150, 200, 300, 400, 
               
               
                   
                 500, 1000, 2000, 2500, 4000, 5000 ppm; 
               
               
                   
                 1%, 2%, 10% by Vol., 10%, 25%, 
               
               
                   
                 100% LEL 
               
               
                 Anisole 
                 100 ppm 
               
               
                 Arsenic Pentafluoride 
                 5 ppm 
               
               
                 Arsine 
                 1, 10 ppm 
               
               
                 Benzene 
                 50, 75, 100, 1000 ppm; % LEL 
               
               
                 Biphenyl 
                 50%, 100% LEL 
               
               
                 Boron Trichloride 
                 500 ppm 
               
               
                 Boron Trifluoride 
                 500 ppm 
               
               
                 Bromine 
                 20 ppm 
               
               
                 Butadiene 
                 50, 100, 3000 ppm; % LEL 
               
               
                 Butane 
                 400, 1000 ppm; 100%, 200% LEL 
               
               
                 Butanol 
                 1000 ppm, 100% LEL 
               
               
                 Butene 
                 100% LEL 
               
               
                 Butyl Acetate 
                 100 ppm; % LEL 
               
               
                 Carbon Disulfide 
                 50, 60, 100 ppm; 5% by Volume 
               
               
                 Carbon Monoxide 
                 50, 100, 150, 200, 250, 300, 500, 1000, 
               
               
                   
                 3000, 5000 ppm; 3%, 5% by Volume, % 
               
               
                   
                 LEL 
               
               
                 Carbon Tetrachloride 
                 50, 100, 10000 ppm 
               
               
                 Cellosolve Acetate 
                 100 ppm 
               
               
                 Chlorine 
                 10, 20, 50, 100, 200 ppm 
               
               
                 Chlorine Dioxide 
                 10, 20 ppm 
               
               
                 Chlorobutadiene 
                 100% LEL 
               
               
                 Chloroethanol 
                 200 ppm 
               
               
                 Chloroform 
                 50, 100, 200 ppm 
               
               
                 Chlorotrifluoroethylene 
                 100% LEL 
               
               
                 Cumene 
                 100% LEL 
               
               
                 Cyanogen Chloride 
                 20 ppm 
               
               
                 Cyclohexane 
                 100 ppm, 100% LEL 
               
               
                 Cyclopentane 
                 50 ppm 
               
               
                 Deuterium 
                 50%, 100% LEL 
               
               
                 Diborane 
                 10, 50 ppm 
               
               
                 Dibromoethane 
                 50 ppm 
               
               
                 Dibutylamine 
                 100% LEL 
               
               
                 Dichlorobutene 
                 1% by Volume 
               
               
                 Dichloroethane (EDC) 
                 50, 100 ppm, % LEL 
               
               
                 Dichlorofluoroethane 
                 100, 1000 ppm 
               
               
                 Dichloropentadiene 
                 50 ppm 
               
               
                 Dichlorosilane 
                 50, 100 ppm 
               
               
                 Diesel Fuel 
                 50 ppm; 100% LEL 
               
               
                 Diethyl Benzene 
                 100% LEL 
               
               
                 Diethyl Sulfide 
                 10 ppm 
               
               
                 Difluorochloroethane 
                 100% LEL 
               
               
                 Difluoroethane (152A) 
                 100% LEL 
               
               
                 Dimethyl Ether 
                 100% LEL 
               
               
                 Dimethylamine (DMA) 
                 30, 50 ppm 
               
               
                 Epichlorohydrin 
                 50, 100, 500, 1000 ppm 
               
               
                 Ethane 
                 1000 ppm 
               
               
                 Ethanol 
                 200, 1000, 2000 ppm; % LEL 
               
               
                 Ethyl Acetate 
                 200, 1000 ppm; % LEL 
               
               
                 Ethyl Benzene 
                 200 ppm; % LEL 
               
               
                 Ethyl Chloride 
                 100 ppm; % LEL 
               
               
                 Ethyl Chlorocarbonate 
                 1% by Volume 
               
               
                 Ethyl Ether 
                 100, 800, 1000 ppm; % LEL 
               
               
                 Ethylene 
                 100, 1000, 1200 ppm; % LEL 
               
               
                 Ethylene Oxide 
                 5, 10, 20, 30, 50, 75, 100, 150, 200, 
               
               
                   
                 300, 1000, 1500, 2000, 3000 ppm; % 
               
               
                   
                 LEL 
               
               
                 Fluorine 
                 20, 100 ppm 
               
               
                 Formaldehyde 
                 15, 50, 100, 500, 1000 ppm 
               
               
                 Freon-11 
                 1000, 2000, 5000 ppm 
               
               
                 Freon-12 
                 1000, 2000, 3000 ppm 
               
               
                 Freon-22 
                 100, 200, 500, 1000, 2000 ppm 
               
               
                 Freon-113 
                 100, 200, 500, 1000, 2000 ppm; 1% by 
               
               
                   
                 Vol. 
               
               
                 Freon-114 
                 1000, 2000, 20000 ppm 
               
               
                 Freon-123 
                 1000 ppm 
               
               
                 Fuel Oil or Kerosene 
                 100% LEL 
               
               
                 Gasoline 
                 100, 1000, 2000, 20000 ppm; % LEL 
               
               
                 Germane 
                 10, 50 ppm 
               
               
                 Heptane 
                 1000 ppm, % LEL 
               
               
                 Hexane 
                 50, 100, 200, 2000, 2500, 3000 ppm, % 
               
               
                   
                 LEL 
               
               
                 Hexene 
                 % LEL 
               
               
                 Hydrazine 
                 5, 10, 20, 100, 1000 ppm, 1% by 
               
               
                   
                 Volume 
               
               
                 Hydrogen 
                 50, 100, 200, 500, 1000, 2000, 5000 ppm; 
               
               
                   
                 3%, 5% by Vol., 2% to 100% LEL 
               
               
                 Hydrogen Bromide 
                 50 ppm 
               
               
                 Hydrogen Chloride 
                 50, 100, 200, 400, 500, 1000 ppm 
               
               
                 Hydrogen Cyanide 
                 20, 30, 50, 100, 200, 1000, 10000 ppm 
               
               
                 Hydrogen Fluoride 
                 20, 50, 100, 200 ppm 
               
               
                 Hydrogen Sulfide 
                 5, 10, 20, 30, 50, 100, 300, 1000 ppm; 
               
               
                   
                 % LEL 
               
               
                 Isobutane 
                 1000, 3000 ppm, % LEL 
               
               
                 Isobutylene 
                 % LEL 
               
               
                 Isopentane 
                 1000 ppm 
               
               
                 Isoprene 
                 % LEL 
               
               
                 Isopropanol 
                 200, 400, 500, 1000 ppm; % LEL 
               
               
                 JP4 
                 1000 ppm; % LEL 
               
               
                 JP5 
                 1000, 5000 ppm, % LEL 
               
               
                 Methane 
                 100, 200, 1000, 1500, 2000, 5000 ppm; 
               
               
                   
                 1%, 2% by Volume, 100%, 200% LEL 
               
               
                 Methanol 
                 200, 300, 400, 500, 1000, 2000, 5000 ppm; 
               
               
                   
                 15%, 30%, 100% LEL 
               
               
                 Methyl Acetate 
                 30 ppm 
               
               
                 Methyl Acrylate 
                 60 ppm 
               
               
                 Methyl Bromide 
                 20, 50, 60, 100, 500, 1000, 10000; 
               
               
                   
                 40,000 ppm 
               
               
                 Methyl Butanol 
                 % LEL 
               
               
                 Methyl Cellosolve 
                 % LEL 
               
               
                 Methyl Chloride 
                 100, 200, 300, 2000, 10000 ppm; % LEL 
               
               
                 Methyl Ethyl Ketone 
                 100, 500, 1000, 4000 ppm; 100% LEL 
               
               
                 Methyl Hydrazine 
                 5 ppm 
               
               
                 Methyl Isobutyl 
                 200, 500, 2000 ppm; 50%, 100% LEL 
               
               
                 Ketone 
               
               
                 Methyl Mercaptan 
                 30 ppm 
               
               
                 Methyl Methacrylate 
                 100 ppm; % LEL 
               
               
                 Methyl-Tert Butyl 
                 100% LEL 
               
               
                 Ether 
               
               
                 Methylene Chloride 
                 20, 100, 200, 300, 400, 500, 600, 1000, 
               
               
                   
                 2000, 3000, 5000 ppm; % LEL 
               
               
                 Mineral Spirits 
                 200, 3000 ppm; % LEL 
               
               
                 Monochlorobenzene 
                 100% LEL 
               
               
                 Monoethylamine 
                 30, 100, 1000 ppm 
               
               
                 Morpholine 
                 500 ppm 
               
               
                 Naptha 
                 1000 ppm, 100% LEL 
               
               
                 Natural Gas 
                 1000, 2000 ppm; 2%, 4% by Volume, % 
               
               
                   
                 LEL 
               
               
                 Nitric Oxide 
                 20, 50 ppm 
               
               
                 Nitrogen Dioxide 
                 20, 50, 100 ppm 
               
               
                 Nitrogen Trifluoride 
                 50, 500, 1000 ppm 
               
               
                 Nonane 
                 2000 ppm 
               
               
                 Pentane 
                 200, 1000 ppm, % LEL 
               
               
                 Perchloroethylene 
                 200, 1000, 2000, 20000 ppm 
               
               
                 Phenol 
                 100 ppm 
               
               
                 Phosgene 
                 50 ppm 
               
               
                 Phosphine 
                 3, 5, 10, 20, 30, 50 ppm 
               
               
                 Phosphorus 
                 200 ppm 
               
               
                 Oxychloride 
               
               
                 Picoline 
                 % LEL 
               
               
                 Propane 
                 100, 1000 ppm; 100% LEL 
               
               
                 Propylene 
                 100, 200, 1000, 5000 ppm; % LEL 
               
               
                 Propylene Oxide 
                 100 ppm,; % LEL 
               
               
                 Silane 
                 10, 20, 50 ppm 
               
               
                 Silicon Tetrachloride 
                 1000 ppm 
               
               
                 Silicon Tetrafluoride 
                 1000 ppm 
               
               
                 Styrene 
                 200, 300 ppm; % LEL 
               
               
                 Sulfur Dioxide 
                 50, 100 ppm 
               
               
                 Tetrahydrofuran 
                 200, 300, 1000 ppm; % LEL 
               
               
                 Tetraline 
                 100 ppm 
               
               
                 Toluene 
                 50, 100, 200, 500, 2000, 5000 ppm; % 
               
               
                   
                 LEL 
               
               
                 Toluene Diisocyanate 
                 15 ppm 
               
               
                 Trichloroethane 
                 50, 100, 500, 1000 ppm; 1% by Volume 
               
               
                 Trichloroethylene 
                 50, 100, 200, 300, 500, 1000, 2000 ppm; 
               
               
                   
                 % LEL 
               
               
                 Triethylamine (TEA) 
                 100 ppm 
               
               
                 Trifluoroethanol 
                 25, 100 ppm 
               
               
                 Trimethylamine (TMA) 
                 50 ppm 
               
               
                 Tungsten Hexafluoride 
                 50 ppm 
               
               
                 Turpentine 
                 % LEL 
               
               
                 Vinyl Acetate 
                 1000 ppm; % LEL 
               
               
                 Vinyl Chloride 
                 20, 50, 100, 200, 400, 500, 1000, 4000, 
               
               
                   
                 10000 ppm; 10%, 100% LEL 
               
               
                 Vinylidene Chloride 
                 50 ppm 
               
               
                 Xylene 
                 100, 200, 300, 1000 ppm, 1% by 
               
               
                   
                 Volume 
               
               
                   
               
             
          
         
       
     
         [0047]    Although the present invention has been described with particularity herein, the scope of the present invention is not limited to the specific embodiment disclosed. It will be apparent to those of ordinary skill in the art that various modifications may be made to the present invention without departing from the spirit and scope thereof.