Patent Document

FIELD OF THE INVENTION 
     This invention relates to a panel inspection plug that may be operated to provide an entrance through which a user may insert an inspection probe, device or device attachment into an area requiring inspection, testing and/or sampling, and more particularly to such an inspection plug that can be adapted to fit into an opening or hole within the panel to allow access to an interior environment covered by the panel. 
     BACKGROUND OF THE INVENTION 
     Inspecting a utility system, such as in the electric, gas, telephone, chemical and sewer industries, can be a difficult task. Utility workers routinely inspect, test, repair and sample the contents of underground utility systems which are designed as subsurface structures. Utility workers generally enter or gain access to these subsurface structures through an opening at the surface that is normally covered by a panel or manhole cover. Prior to entering the underground structure, the manhole cover typically must be removed and atmospheric tests performed on the interior environment to ensure that the underground structure is safe to enter, e.g., that little or no toxic substances or combustible gases are present. The inspection may be performed with air and fluid monitors utilizing probes, tubes, etc., that may be used to gather or detect unidentified matter and gasses. Most panels or manhole covers are made of solid cast iron and can weigh from 150 to 450 pounds. Accordingly, removing manhole covers and inspecting the contents of the internal atmosphere can be physically exhausting and dangerous, often resulting in back, leg, or arm injury. 
     To gain access to the interior environment, manhole covers are physically dislodged and at least partially removed from the opening to permit the entry of probes, tubes or other devices. Removing a manhole cover ordinarily requires at least two able-bodied field crew members and specialized tools such as a four to eight foot crow bar, a 10 pound hammer, a sledge hammer, and two manhole hooks. The manhole hooks are normally used to pull the panel or manhole cover from its support structure. However, oftentimes the manhole cover is stuck tightly to its structure or receiving frame due to foreign matter such as dirt, rocks, roadway tar, etc. The specialized tools are used to pry open or pound the cover and frame thereby breaking the seal caused by the foreign matter so that the cover can be successfully dislodged or removed with the manhole hooks. Upon completion of an inspection, workers must return the manhole cover to its support structure by using the manhole hooks and other tools. The repeated manhole cover manipulation, required for even minor utility system inspections, can cause severe or permanent injury to utility workers. 
     Utility companies, especially electric utilities, occasionally experience explosions within their structures. The explosions may be caused, for example, by electric cable failures which may short creating high energy arcing between the cable&#39;s conductors. The arcs may decompose air, water, insulation, or other material in the structure to a flammable or explosive gaseous state. For example, decomposition products such as hydrogen, methane, acetylene, propane, etc. may combine with the underground atmosphere and/or aboveground air entering the structure to create a combustible atmosphere or mixture. As the manhole cover or panel is dislodged, air may suddenly rush into the internal atmosphere and mix with the internal gases to create a combustible gas that may come into contact with an ignition source such as the arc or other intense heat source thereby causing an explosion and/or fire (so-called “backflash”). Moreover, the explosion may also start a fire within the system. The explosion and resulting fire form large amounts of dangerous toxic gases such as carbon monoxide. Because these structures may be connected to other structures through passageways or ductways, the gases may travel to adjacent utility structures and through service ducts thereby entering buildings and homes and endangering people and animals. 
     A utility worker or other individual who must enter a utility system is typically unaware of the contents of the internal atmosphere. Combustible or toxic gases may be present and explode without warning causing serious injury to individuals in the area. Accordingly, a need exists for a device and method for inspecting the contents of an internal atmosphere that does not require removing or dislodging a panel or manhole cover. The need also exists for increasing the accuracy of the inspection and eliminating “backflash”. 
     Similarly, electrical connection boxes such as Electric Main Service Disconnect Switch Enclosures, found in most buildings, may contain combustible or flammable gases. In response to an emergency, an operator such as a firefighter typically operates a main electrical switch or circuit breaker that is located within such a box to disconnect the electricity to the building. However, by turning off the electric supply to the building, an operator may unknowingly produce sparks or arcing between the two internal metal contacts of the switch. This sparking or arcing occurs at the moment the contacts separate from each other due to the potential difference between the metal contacts. The resulting spark or arc may ignite combustible gases that may exist within the connection box and create a dangerous explosion that can severely injure the operator of the switch and damage surrounding equipment. As a result, the operator may be required to remove a cover, panel or door attached to the switch enclosure so that the operator can determine whether it is safe to disconnect the electricity to the building. To remove the cover, panel or door, screws may have to be removed thereby consuming valuable time in an emergency situation. Thus, a need exists for quickly and accurately analyzing the internal atmosphere of a utility system connection box without disassembling and opening its panel, door, cover, or other enclosure in a time consuming manner. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention an inspection plug is provided that can be removably or fixedly inserted into an environment-defining barrier or panel, such as a manhole cover, wall or closure of a containment system. Typically, the barrier or panel includes an opening or hole into which the inspection plug can be inserted. In illustrative embodiments, the plug provides an inspection port and a closure member for the port, the closure member being sufficiently yieldable to permit the insertion of a probe through the inspection port and returning to a closed state after the probe has been extracted. In one embodiment, the inspection plug may include a peripheral shoulder, an openable or movable cap, and a body such as a cylindrical member. The cap may be hingably attached to the shoulder and resiliently biased by normally a spring or spring-like member into a closed position to seal the cylinder opening. In yet other embodiments, the closure member may comprise a resilient insert or cap having openings through which a probe may be inserted, in which the openings automatically seal to its normally closed position when the probe is removed. 
     That is, the present invention provides an inspection closure assembly having a panel with an opening, an inspection plug received within the opening and extending therethrough. The plug has a plug body with a passageway extending between first and second ends thereof and terminating at the first end in a probe-receiving port. The assembly also may include a closure member, which is yieldable to a degree sufficient to admit the insertion of an object such as an inspection probe through the port, for the probe-receiving port. 
     The present invention also provides an inspection closure assembly receivable within a panel opening that extends through a panel. The assembly includes a plug body having a passageway extending between the first and second ends thereof and terminating at the first end in a probe-receiving port. The assembly also may include a resiliently biased cap member oriented at least partially within the probe-receiving port, the cap member being pivotally oriented about a rod-shaped member mounted in the plug body and being yieldable to a degree sufficient to admit the insertion of an object, such as an inspection probe, through the port. 
     The present invention also provides a method of using an inspection plug that includes a resiliently movable cap member, which is located at a port opening and may be within a passageway defined by a cylinder, for closing and opening the probe receiving port. The cap is preferably biased toward the outer surface of the panel such that inward pressure on the cap causes it to open to permit the entrance of a probe into the probe-receiving port or passageway. In addition, the inspection plug assembly may contain a gel material, wherein the cap or a part thereof is made of an elastic or flexible material and contains one or more slits. The cylindrical member contains an elastic or flexible enclosure at the bottom of the inspection plug containing one or more slits to contain and house the gel material. 
     The present invention also provides a method of assembling a panel with an inspection plug having first and second surfaces and an opening extending therethrough. The method includes providing an inspection plug having a plug body defining therein a passageway extending between the ends thereof and terminating at one of the ends in a probe-receiving port, and having a resiliently movable closure member located within the passageway for closing and opening the probe receiving port. The method may additionally include inserting a portion of either of the ends of the body into the panel opening, and securing the plug in the panel opening. 
     The present invention also provides a method of employing an inspection plug having a plug body with a first end, a second end and defining therein a passageway extending between the ends and terminating at the first end in a probe receiving port. The inspection plug also may include a resiliently movable cap member located at least partially within the passageway for closing and opening the probe receiving port. The method includes operating the cap to permit the entrance of a probe into the probe receiving port, and inserting the probe into the passageway of the inspection plug. 
     The plug and cap assembly can be threaded at one extreme to allow attachment to the panel by a lock washer and nut. Alternatively, attachment may be by flexible locking prongs, a locking mechanism, rivet, friction, etc. 
     The present invention also provides for the ability to quickly and easily inspect the contents within the structure by visual means such as with a camera/video system and thus not have the burden to removing or dislodging a heavy cover using cumbersome tools. 
     The present invention also provides a method for inspecting an internal atmosphere using an inspection plug for accessing the internal atmosphere. 
     The present invention also provides an inspection plug and alarm combination and a method for using same. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side cross-sectional view of an inspection plug in accordance with the invention. 
     FIG. 2 is a plan view of the top of the inspection plug. 
     FIG. 3 is an exploded perspective view of the inspection plug, the nut assembly, and a manhole cover. 
     FIG. 4 is a cross-sectional side view of an inspection plug with a nut assembly attached to a manhole cover. 
     FIG. 5 is a cross-sectional side view of the inspection plug showing a probe inserted into the access port by depressing the cap. 
     FIG. 6 is a cross-sectional exploded side view of an alternate embodiment of the inspection plug, with a screw cap closure. 
     FIG. 7 is a cross-sectional side view of an alternate embodiment of the inspection plug, having a pliant port closure. 
     FIG. 8 is an exploded perspective view of an alternate embodiment of the inspection plug, showing a snap-ring attachment member. 
     FIG. 9 is a cross-sectional side view of an alternate embodiment of the inspection plug, with a flexible prong attachment member. 
     FIG. 10 is a cross-sectional side view of an alternate embodiment of the inspection plug, attached to a panel with a rivet-like deformation of the plug. 
     FIG. 11A is a cross-sectional side view of an alternate embodiment of the inspection plug, adapted for attachment to a panel by a C-ring. 
     FIG. 11B is a perspective view of a representative C-ring for use with the embodiment of FIG.  11 A. 
     FIG. 12A is a perspective view of the inspection plug with an alarm adjacent thereto. 
     FIG. 12B is a perspective view of an alarm attached to the inspection plug. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Both the structure and operation of the preferred embodiments of the present invention will now be described in greater detail with reference to the figures. 
     FIG. 1 illustrates the inspection plug, generally designated by reference numeral  102 , in accordance with the present invention. The inspection plug is for attachment to a panel, such as a manhole cover, as will be described herein. In this embodiment of the invention, the inspection plug  102  is comprised of a body  104 , a peripheral shoulder or outwardly directed flange  106 , and an openable cap  108 . The body  104 , peripheral shoulder  106 , and cap  108  may be made of plastic, stainless steel, aluminum, rubber, a composite material, or a combination of such materials that preferably are non-corrosive. The cap  108  is preferably made of stainless steel or aluminum alloy and may be formed by a stamping machine. 
     As shown in FIG. 1, the body  104  of the plug  102  is cylindrical having a top end  110 , a bottom end  112 , and a passage  114  extending axially through the plug between its ends and terminating at an internal ledge  118  proximate to the top end  110 . The top end  110  of the cylindrical member has an inspection internal ledge  118  that defines an aperture  120  of smaller diameter than the passage  114 . An inspection port  120  is sized for inserting an inspection probe or other device into and/or through the inspection plug  102 . The length of the body  104  may vary depending on the thickness of the panel  300  (FIG. 3) to which the inspection plug  102  is to be attached, as illustrated in FIG.  4 . Although described here as being cylindrical, the body  104  may be square, hexagonal, or any shape with a passage through it from one end to the other. 
     The plug has an external peripheral shoulder  106  extending radially outwardly from the accessible end of the plug. When installed on a panel such as a manhole cover, the shoulder  106  may have a tapered top side  122  designed to allow vehicle tires to ride over the inspection plug  102  with minimal impediment and to prevent pedestrians from tripping on the inspection plug  102 . Preferably, the inspection plug can be installed flush mounted as shown in FIG. 4, that is, not protruding on the exterior side  302  (FIG. 3) of the manhole cover or panel. The underside  124  of the shoulder  106  supports the inspection plug  102  when attached to a panel and also helps to locate the inspection plug&#39;s placement in the panel port, opening or hole. The length of the plug may vary depending on the thickness of the panel  300  (FIG. 3) to which the plug  102  is to be attached. Inspection plugs used in electrical connection boxes, or other defined enclosures, which usually have thin walls, will be relatively short in length, e.g., about ¾ inch from the top end  110  to the bottom end  112 . However, the plugs used in manhole covers will usually be longer in length, e.g., about 3 inches. Naturally, this invention can be miniaturized depending on the needs of the particular device requiring inspection. 
     The openable cap  108  within the aperture  120  forms a hat-shaped body having a circular disc  126  sized for insertion into the aperture  120 . The edge of the circular disc  126  curves downward and forms a cylindrical body  128  of about the same diameter as the circular disc  126 . The bottom of the cylindrical body  128  curves outward into a radially extending rim  130  having a diameter greater than the aperture  120  and smaller in diameter than the passageway  114 . A gasket may be fitted to the top side  131  of rim  130  to provide an improved seal between the cap  108  and the internal ledge  118  when the inspection plug  102  is not in use and its cap is in the normally closed position. A portion of the rim  130  extends laterally to form one or more pivot arms  132  as depicted in FIG.  2 . The pivot arms  130  wrap partially around a spring pin  134  thereby creating a hinge axis. Preferably, two pivot arms  132  extend parallel to each other from the rim  130  to the spring pin  134  as illustrated in FIG.  2 . In this embodiment, the cap  108  is hingably attached through the spring pin  134  to the cylindrical member. In other embodiments, the cap may be of a different shape, e.g., flat disk, square, hexagonal, etc. 
     The spring pin  134  is located in a spring compartment  136  located within a portion of the body  104 . A spring  138  having an inner end  140  and an outer end  142  is wound around the spring pin  134  and cooperates with the cap  108 . The inner end  140  of the spring  138  extends generally toward the center of the circular disc  126  and applies a resilient upward pressure against the underside of the circular disc  126  thereby causing the radially extending rim  130  to normally press against the internal ledge  118 . Thus, the cap  108  is normally biased in a closed position as illustrated in FIG.  1 . The outer end  142  of the spring  138  extends generally away from the cap  108  and contacts the edge  144  of a downwardly facing step  146  located in the spring housing compartment  136 . The spring  138  may be made of stainless steel or music wire. Although described here in terms of a horizontally coiled spring mechanism, other spring-type embodiments may be used in the present invention to exert a force for facilitating closure of the cap. 
     The spring compartment  136  has a side slot  156  which facilitates access to the spring compartment  136 . The spring  138  and spring pin  134  may be inserted into the spring housing compartment  136  through the side slot  156  during assembly of the inspection plug  102 . The cap  108  can be inserted through the body  104  passageway  114  for assembly. The spring pin  134  is then attached by spot welding, liquid steel, glue, epoxy, or similar means to the sides of the spring housing compartment  136 . FIG. 2 illustrates an appropriate position for the spring pin  134  in the spring housing compartment  136 . Of course, the pin also can be threaded and screwed into a drilled and tapped hole in the body (not shown). If desired, the cap can be provided with a locking mechanism, such as a simple tab that can be pivoted into engagement with a slot in the way of the aperture  120  to prevent accidental depression of the cap. Alternatively, a locking tab can be pivotally mounted on the plug body for locking engagement with the cap. 
     As shown in FIG. 3, the inspection plug  102  may be attached to a panel  300  in one of several ways. The term “panel” as used herein shall be understood in a relative sense and is intended to designate any movable or fixed partition, such as a manhole cover or connection box wall, that partially or totally obscures an area requiring inspection. The term “connection box” as used herein shall also be understood in a relative sense and is intended to designate a substantially enclosed box including, but not limited to, the following: electric meter service boxes, electric switchgear panels, metering closets, electrical throughputs, electric service shut-off switches, circuit breaker boxes, main breaker panels and transformer cubicles. The panel  300 , as illustrated in FIG. 3 has an exterior side  302 , an interior side  306 , and a hole  304  having a diameter slightly larger than the diameter of the inspection plug body. The panel  300  also has a circular shelf  312 , illustrated in FIG. 4, designed to accommodate the peripheral shoulder  106  of the inspection plug  102 . The circular shelf  312  allows the peripheral shoulder  106  to be recessed or submerged in the panel  300 . This embodiment minimizes disturbances, possible tripping, etc. created when automobiles or pedestrians pass over the plug. 
     The inspection plug  102  may also be attached to the panel  300  by force-fitting the plug  102  into the panel hole  304 . This embodiment is preferred when the plug  102  is made of a soft or malleable metal or other relatively soft material. The plug  102  may also be affixed to the hole  304  in the panel  300  by glue, epoxy, liquid steel, mechanical crimping, or similar affixing arrangements. 
     The inspection plug  102  may be attached to the panel  300  by a nut assembly, which includes a washer  148 , a nut  150 , and optionally a gasket (not shown). In this embodiment, illustrated in FIGS. 3 and 4, the cylindrical member has a threaded exterior portion  152  near its bottom end  112 . The nut  150  has a threaded bore  154  for engagably receiving the threaded exterior portion  152  of the cylindrical member. To attach the inspection plug  102  to the panel  300 , the user inserts the bottom end  112  of the plug into the hole  304  in the panel  300  until the under-side  124  of the peripheral shoulder  106  contacts the exterior side  302  of the panel  300  at which point the threaded exterior portion  152  of the cylindrical member will extend into the internal atmosphere  308 , which is the area requiring inspection. A gasket made of rubber, plastic, composite material, or other material, may optionally then be placed over the bottom end  112  of the plug  102  to improve the seal between the plug  102  and the washer  148  and/or nut  150 . The washer  148  is then placed over the threaded exterior portion  152  of the cylindrical member, and the nut  150  is screwed onto the threaded exterior portion  152  of the cylindrical member of the inspection plug  102  thereby securing the inspection plug  102  to the panel  300  as illustrated in FIG.  4 . 
     To use the invention, as illustrated in FIG. 5, the user inserts an inspection probe  502  through the aperture  120  into the internal atmosphere  308 . By applying pressure against the top edge of the circular disc  126 , the spring force is overcome and the cap will open on its hinge axis. As it opens, the user may further insert the inspection probe  502  or other device through the inspection plug  102  and into the internal atmosphere  308 . After the inspection probe  502  has been inserted to required depths, the user may inspect the contents of the internal atmosphere  308 . After the inspection is complete, the probe is retracted from the inspection plug whereby the cap proceeds to its normally closed position by the force exerted by the internal spring member and seals the entranceway thereby substantially preventing dirt, water, or other contaminants from entering the structure. 
     Additionally or alternatively, the radius of the hole  114  in the body  104  may gradually decrease or taper from the top end  110  of the cylindrical member to the bottom end  112  of the cylindrical member thereby aiding in guiding the inspection probe  502  or other device through the hole  114  of the inspection plug  102  and into the internal atmosphere  308 . 
     In an alternate embodiment, illustrated in FIG. 6, the openable cap is a threaded insert  602  which may be unscrewed from the inspection plug  102  to allow the user to insert the inspection probe or other device into the hole  114 . In this embodiment, the outer surface of the insert  602  is threaded to mate with interior threads  604  of the inspection port  120 . To gain access to the interior environment, a user unscrews the insert  602  by hand, screwdriver, or other device, and removes it from the inspection plug  102 . Once the inspection is complete, the user closes the inspection plug  102  by screwing the insert  602  back into the inspection plug  102 . 
     In the embodiment of FIG. 7, the interior of the plug body  104  is filled with a gel material  710 , the purpose of which is to provide a probe-penetrable seal at the inspection plug. In this embodiment, the closure of the inspection port is an elastic or resilient flexible top insert  702  having one or more slits  704  sized for receiving inspection probes or other devices. The bottom end  112  of the body  104  has a similar elastic or flexible resilient insert  706  which normally substantially seals the hole  114  and similarly contains one or more slits  708  sized for receiving inspection probes or other devices. The gel material  710  occupies the volume within the hole  114  between the inserts  702  and  706 . The interior space of the plug may be filled with the gel material  710  through either of these slits with a syringe or other device. Alternatively, one of the closure inserts may be put in place after the gel material  710  is loaded. In either case, the inserts house the gel to allow the user to insert and retract an inspection probe or other device through the inspection plug  102 . 
     The gel material is preferably self-adhering or has other adhesive characteristics for sticking to the internal wall of the body and thereby minimizing flow or leakage while maintaining a paste-like consistency. The material can be formed of silicone polymers to form a silicone grease-like formulation such as silicone sealants. The gel material preferably has the following characteristics: water repellency, atmospheric and chemical resistance, good elasticity, and thermal resistance over a wide temperature range. 
     The flexible top insert described above also may be employed in non-gel embodiments of the present invention. The cap or top closure element may be made of an elastic or flexible material such as a foam, rubber, or neoprene material and fixed within the port  120  by glue, epoxy, or other adhesive. Alternatively, inwardly directed flanges at the periphery of the port  120  can be provided to securely locate a resilient or compressible top closure element within the inspection port. 
     In another embodiment, illustrated in FIG. 8, the plug body  104  may be secured to the panel  300  by a bayonet-type lock member  802 . In this embodiment, the outer surface of the body  104  includes a plurality of radially extending tabs  804  at its lower end. A plurality of tab-mating slots  808  in the inner wall  810  of the lock member bore  806  are spatially aligned with the tabs  804 . Of course, the tabs and slots can also reverse positions, with tabs on the lock member and complementary slots in the plug body. To attach the body  104  to the panel  300 , the body  104  is inserted through the hole  304  in the panel  300 , and the slots  808  on the lock member  802  are aligned with the tabs  804  on the body  104 . The slots  808  receive the tabs  804 , after which the inspection plug  102  may be rotated so that the tabs and slots are engaged. 
     In another alternative embodiment, illustrated in FIG. 9, the inspection plug  102  is attached to the panel  300  by flexible prongs  902  that are dimensioned to engage the underside of the panel and that radially compress as the plug is inserted through the panel hole. Once in place, the prongs snap outwardly into place. In this embodiment, the body  104  is formed with one or more inwardly compressible resilient prongs  902  extending from the exterior end to the interior end of the plug. Each prong  902  includes a shaft  904  terminating in a barb or clasp hook  906 . The clasp hook  906  preferably tapers to a point  908  in the direction of the bottom end  112  of the body  104  to provide a camming surface for directing the prongs inwardly as the plug is inserted into the panel hole. Thus, as the inspection plug  102  is inserted into the panel hole  304 , the clasp hook  906  will be forced inwardly causing the shaft  904  to yield radially inwardly. To that end, the plug body, or simply the prongs  902  are constructed of a resilient material such as spring steel or plastic, having strong elastic memory properties. Once the clasp hooks  906  pass the internal side  306  of the panel  300 , they snap radially outward thereby securing the inspection plug  102  to the panel  300 . One benefit of this embodiment is that an inspection plug  102  may be quickly inserted into pre-existing holes  304  without panel  300  modification or manipulation. 
     The inspection plug may also be attached to the panel  300  through a solid impact riveting process as shown in FIG.  10 . In this embodiment, the cylindrical member is formed of a malleable metal. In solid impact riveting, a compressive axial load is applied to the end of the rivet shank  1004  (here, the cylindrical body) causing the shank  1004  to swell throughout its length as it shortens under the load. The rivet shank  1004  continues to expand until the walls  006  of the panel port or bole  304  restrict the shank  1004  from further radial expansion. The unrestricted rivet end outside the panel port or hole  304  then expands, forming a rivet clinch  1002  which secures the cylindrical member to the panel  300 . 
     In another embodiment, the plug shown in FIG. 11A may be attached to the panel using a “C-ring,” which is illustrated in FIG.  11 B. In this embodiment, the C-ring  1102  is a solid flexible or malleable semi-circular disc made of plastic, stainless steel, aluminum or a composite material. The C-ring  1102  is sized for engaging a circular groove  1104  in the outer wall of the cylindrical member which extends around the cylindrical member parallel to the top end  110  and the bottom end  112  of the body  104 . The circular groove  1104  is oriented on the cylindrical member such that the distance between the downwardly facing side  124  of the peripheral shoulder  106  and the circular groove  1104  is equal to or slightly greater than the width of the panel  300 . To attach the plug to the panel  300 , the plug is inserted into the hole  304  in the panel  300 . The open end  1106  of the C-ring  1102  is then aligned with the circular groove  1104  and pressed against the cylindrical member until the C-ring  1102  snaps onto the cylindrical member and rests partially within the circular groove  1104 . 
     In various alternate embodiments, the cap  108  may be situated at or near the bottom end  112  of the body  104 . Similarly, the peripheral shoulder  106  may be situated at the bottom end  112  of the body  104 . Accordingly, the nut assembly or other attaching mechanism may be located at the top end  110  of the body  104 . 
     The inspection plug may be used in conjunction with an alarm system as illustrated in FIG.  12 A. An alarm  1204 , which may detect toxic, flammable or combustible gases or detect the buildup of a particular gas, is also attached to the panel wall  1200  in close proximity to the inspection plug. Alternatively, the alarm  1204  may be positioned directly over the interior portion of the inspection plug as shown in FIG.  12 B. Additionally, the alarm  1204  may have a warning light  1206  which passes through a second hole  1208  in the panel. The warning light may indicate that a concentration of a certain gas has been exceeded or that the battery is low, or that no source exists. By orienting the alarm and the inspection plug together or near one another, a user can easily test the internal atmosphere of an area requiring inspection. For example, if the alarm detects that a certain concentration of an undesirable (or desirable) gas has been exceeded, the alarm sounds and/or the warning light becomes lit thereby informing the user that the predetermined gas concentration has been exceeded. Subsequently, the user may insert an inspection probe into the inspection plug to inspect the contents of the internal atmosphere and measure the concentration of gaseous mixture therein. 
     The alarm  1204  and inspection plug  1202  combination may be attached to a panel wall  1200  through any of the above-described attaching methods. As shown in FIG. 12A, a first nut  1210  may be used to attach the plug to the panel. If the alarm  1204  is placed directly over the inspection plug, a second nut  1212  may be used to secure the alarm wall  1214  to the inspection plug  1202  as shown in FIG.  12 B. 
     Having described the invention in detail, those skilled in the art will appreciate that modifications may be made without departing from the spirit and scope of the invention. Therefore, it should be understood that the scope of the invention is not limited to the specific embodiments illustrated and described but is defined in the appended claims.

Technology Category: b