Patent Publication Number: US-6656434-B1

Title: Compact portable owner-serviced air duct sanitizing system

Description:
BACKGROUND 
     1. Field of Invention 
     This invention relates to devices used for sanitizing air conditioning and heating system ducts, specifically to a compact user-friendly, portable air duct sanitizing apparatus and method, for new construction as well as retrofitting to existing air conditioning and heating systems in commercial and residential buildings, which can be either professionally or owner installed, with routine maintenance thereafter being easily and safely performed by the owner or other non-professional. The sanitizing apparatus of the present invention comprises a system control unit with a housing that supports a refillable non-pressurized reservoir of liquid sanitizing agent, which is removably attached to the housing without opening the housing cover. In addition the housing supports and protects a 24-volt electric pump capable of moving fluid through tubing at a pressure of approximately 60 psi and a fully automated 24-volt programmable timer with power loss backup. The sanitizing apparatus also comprises a plurality of misting nozzles each capable of creating a fine mist having droplets with a maximum diameter dimension of approximately 250μ. Each misting nozzle is connected via tubing between the pump and one of the air ducts targeted for sanitizing, with at least one misting nozzle being inserted into each of the air ducts, as well as into the main plenum to which the air ducts are connected. When more than one air duct is targeted for sanitizing, the misting nozzles are connected to a branching array of fluid carrying tubing rated to withstand a maximum pressure of approximately 200 psi that has a trunk line connected to a single hose fitting on the pump. The pump in each system control unit housing is selected to provide liquid sanitizing agent to a maximum of approximately six air ducts. In addition, the present invention also comprises electrical connection means between the 24-volt programmable timer and the air handler of the air conditioning or heating system with which it is associated that allows the sanitizing apparatus to be internally powered through the associated air conditioning or heating system. The system control unit housing of the present invention is preferably mounted in commercial or residential structures in a location remote from the air conditioning ducts, where it can be easily accessed for timer reprogramming and fluid reservoir exchange or refill. The fine mist entering the air ducts is evenly dispersed therein by the fan of the associated air conditioning or heating system, to coat the inside of the air ducts so as to kill bacteria, viruses, fungi, yeast, algae, molds, and mildew over a period of time and thereafter maintain the air ducts in a sanitized condition. As a result, the air duct sanitizing apparatus of the present invention also comprises a fan relay to by-pass the air conditioning or heating system thermostat during such time when the fan is not in an operating mode and it is needed to assist in mist dispersal. Optional use of a planar polyvinyl chloride (PVC) mounting board for electrical components that is removable from the housing not only facilitates manufacture by making it easier for the people assembling the present invention to connect the wiring between electrical components, it also facilitates servicing and replacement of electrical components since the mounting board is easily releasable from the installed housing, typically by unfastening the nuts respectively attached to two bolts. Safety features of the present invention include the high-pressure rated tubing, the reduced voltage timer and pump, a pump that safely operates wet or dry should the operator fail to anticipate timely replacement or refill of the reservoir before all of the fluid therein is completely used, the pump also having a fluid loop should the fluid discharge opening of the pump become inadvertently blocked, and the non-pressurized supply of low toxicity non-flammable sanitizing agent. Although not limited thereto, chlorine dioxide is the sanitizing agent preferred for use with the present invention, as it has a low toxicity and a category III EPA safety rating. In addition to air duct sanitizing, the present invention can also be used for air purification and aromatherapy. 
     2. Description of Prior Art 
     The interior walls of the air ducts of ventilation systems are subject over time to the accumulation of particulate matter, as well as the growth of algae, yeast, fungi, bacteria, molds, and mildew. Also, the air drawn through such ducts may contain bacteria and viruses that are so small in size they cannot be removed by filtration. As a result, the continued recycling of air with no conditioning other than filtration can lead to high levels of allergens and other contaminants in ventilation system ducts that can cause those sensitive to them to experience discomfort and/or become ill. Systems to sanitize and condition air in ventilation systems are known. However, most are expensive and/or require professional installation, maintenance, or both. The present invention comprises an air duct sanitizing, de-odorizing, conditioning, and purification system that is user-friendly and has a compactly configured lightweight system control unit housing that can be installed by a non-professional in any location convenient for easy maintenance access. The present invention also has built-in safety features that allow essentially risk-free routine owner maintenance and use. Further, through simple exchange of the non-pressurized fluid reservoir for one containing a different chemical solution, and easy adjustments made to the programmable timer, alternative uses of the present invention can include aromatherapy and air purification. 
     The invention thought to be the closest in concept to the present invention is the invention disclosed in U.S. Pat. No. 5,281,401 to Bryson, Sr. (1994). However, many important differences exist between the Bryson, Sr. invention and the present invention. The Bryson, Sr. invention comprises a container with a one-way valve for permitting the inflow of air into the container, a pressurized cartridge positioned within the container and adapted for dispensing a vapor into the container, an intermittently operable air and vapor pump, a timer for intermittent activation of the pump with the periods of operation and non-operation being independently variable, and conduit for conveying the air and vapor mixture between the container and the pump, as well as between the pump and an air duct. When multiple segments of conduit are joined, the Bryson, Sr. invention contemplates the use of a valve to adjust the vapor flow into various portions of the conduit. Also, in the Bryson, Sr. invention two independent timers are preferred, one to control the operation time and the other to control the non-operation time. The control box for the Bryson, Sr. invention may be attached directly to the outside surface of an air duct, or in the alternative situated remotely from the duct into which the Bryson, Sr. invention directs its air and vapor mixture. Also, a power supply cord in the Bryson, Sr. invention electrically connects the pump and timer to a standard electrical outlet. As the liquid in the cartridge is spent, the amount of vapor in the canister after a period of rest will become reduced. As a result, timer adjustment is required in the Bryson, Sr. invention when the cartridge fluid level is reduced to allow for more uniform distribution of the vapor. In contrast, the present invention comprises a fully automated 24-volt programmable timer with power loss backup, a non-pressurized reservoir of liquid sanitizing agent which can be refilled or replaced by a new reservoir having the same or different liquid sanitizing or aromatherapy agent, a plurality of nozzles each capable of creating a mist of droplets having a maximum diameter dimension of approximately 250μ with at least one of the nozzles being inserted into each of the air ducts targeted for sanitizing and at least one nozzle being inserted into the main plenum to which the air ducts are connected, each nozzle being attached on the distal end of a segment of fluid carrying tubing rated at approximately 200 psi that is connected between the pump and the air duct or main plenum, and electrical connection means between the 24-volt programmable timer and the air handler of the air conditioning or heating system that allows the sanitizing apparatus to be internally powered thereby at reduced voltage without the limitation of having to position the system control unit housing near to an electrical outlet or the further expense of a step-down transformer to convert municipally provided higher voltage electricity to the lower 24-volt alternating current required for safe non-professional operator use. The pump of the present invention is optimally used with no more than a maximum of approximately six misting nozzles for uniform and effective mist coating of air duct interior surfaces. The present invention has no mixing chamber for air and vapor similar to the Bryson, Sr. invention, and no one-way valve to draw air into a vapor-filled chamber which when subjected to vacuum pressure creates an air and vapor mixture that is then circulated by a pump through conduit for dispensing into the atmosphere of an air duct. Instead, the present invention pump is used to draw sanitizing liquid through various branching segments of tubing each ending in a misting nozzle. The mist is only created as the liquid is forced through the nozzles. Thus, since there is no vapor in the fluid reservoir and it is not a mixing chamber, no timer adjustment is required to maintain a threshold level of vapor in the fluid reservoir for mixing and distribution as the sanitizing agent is consumed. Further, a fan relay is used to by-pass the thermostat of the air conditioning or heating system with which the present invention is associated to activate its fan when the fan is not already in an operational mode so that the fan can run concurrently with the pump and be used to disperse the 250μ or smaller mist droplets evenly throughout the air ducts. In addition to the fan relay, the present invention also comprises a full bridge rectifier that is not disclosed in the Bryson, Sr. invention. The pump of the present invention is also adapted to operate safely wet or dry should the owner forget to exchange or refill the removable reservoir before all of the sanitizing fluid therein is completely used. Also, for operator safety and to avoid pump failure, the pump has a fluid by-pass loop in the event that its discharge opening becomes inoperable for any reason, and the electrical components may optionally be attached to a planar mounting board releasable from the system control unit housing for ease in manufacture as well as servicing convenience. No air duct sanitizing systems are known that have all of the advantages offered by the present invention. 
     SUMMARY OF INVENTION—OBJECTS AND ADVANTAGES 
     The primary object of this invention is to provide an air duct sanitizing system that safely and thoroughly kills bacteria, viruses, algae, fungi, yeast, mold, and mildew with continued use in both residential and commercial buildings. It is a further object of this invention to provide an air duct sanitizing system that is lightweight and compact in configuration with components selected for safe and easy installation, operation, and maintenance by professionals as well as non-professionals. It is also an object of this invention to provide an air duct sanitizing system that is user-friendly and reliable, requiring minimal operator maintenance or attention after initial installation. A further object of this invention is to provide an air duct sanitizing system that is effectively used in new construction, and can also be easily retrofitted to the air ducts in existing air conditioning and heating systems. It is also an object of this invention to provide an air duct sanitizing system with a system control unit that has only reduced voltage electrical connections to enhance the safety of non-professional operators. It is also an object of this invention to provide an air duct sanitizing system that can be quickly converted for aromatherapy applications, as well as air purification applications wherein the chemicals used require temporary building evacuation and a cure period. 
     As described herein, properly manufactured and used, the present invention would provide an air duct sanitizing system and method for the safe and thorough killing of bacteria, viruses, algae, fungi, yeasts, mold, and mildew with continued use, and could alternatively be put to aromatherapy or air purification use. Liquids approved by the U.S. Environmental Protection Agency for air duct sanitizing purposes, such as but not limited to low toxicity non-flammable chlorine dioxide, would be periodically dispensed by the present invention into the air ducts of populated buildings and dispersed by the fan of the air conditioning or heating system with which the present invention is associated so that the mist droplets of chlorine dioxide evenly coat the interior surfaces of the air ducts targeted for sanitization. Once the present invention was installed either professionally or by the owner, the professional operator, building owner, or other non-professional maintenance personnel could easily maintain its function by periodically refilling the fluid reservoir or simply exchanging an empty reservoir for a new one. Due to its low category III safety rating, when chlorine dioxide is used as the sanitizing agent for the present invention, discarded fluid reservoirs would not require any special handling or disposal. In the alternative, when air purification is required, it could be accomplished by simple exchange of the removable fluid reservoir for one providing the appropriate air purification chemical, temporary evacuation of occupants from the building, and continued circulation of the air purification mist through the air ducts and building for a predetermined period of time, followed by a cure period sufficient to allow dissipation of chemicals to the safe level required for renewed human occupancy. The same quick conversion of the present invention into an aromatherapy system can be achieved by simple exchange of a fluid reservoir filled with sanitizing agent and replacement with a fluid reservoir providing the appropriate non-pressurized aromatherapy liquid, as well as easily performed timer adjustment, if required. In the alternative, pleasing scents can be added to the air duct sanitizing agent to achieve aromatherapy objectives. While the present invention is suitable for new construction, it can also be easily retrofitted to existing air conditioning and heating systems since it comprises a compact pre-assembled system control unit and an easily constructed branching array of fluid carrying tubing that contains a misting nozzle within each of its distal ends so that a mist having droplets with a maximum diameter dimension of approximately 250μ is directly injected into the main plenum, as well as into each individual air duct connected to the main plenum. The nozzle-duct connections are purposefully made close to the main plenum to best achieve a thorough coating of mist on all interior surfaces of each air duct. The tubing can be made into a variety of suitable branching configurations through the use of T-shaped hose connectors. Electrical outlet access is not a concern in positioning the sanitizing system control unit housing, since a direct electrical connection is made between the air handler of the associated air conditioning system and the sanitizing system control components that allows the present invention to be internally powered through the associated air conditioning or heating system. Such internal power connection also reduces the cost of the system control unit as it eliminates the need for a step-down transformer to provide the 24-volt reduced level of power desired within the system control unit for operator safety. Should a building have multiple air conditioning or heating zones to manage airflow, it is contemplated for one of the present invention air duct sanitizing systems to be used in association with each zone. The system control unit housings used in each zone could then be consolidated in one location for efficient maintenance, or in the alternative they could be located independently from one another, as dictated by available space or as otherwise desired. The sanitizing system control unit housings are lightweight and compact, and therefore easily mounted to most surfaces. Also, since they are made from plastic, such as polypropylene, they are virtually maintenance-free and resistant to the corrosive nature of some of the chemicals used to sanitize air ducts. Connection of the misting nozzles to the air ducts can be easily accomplished by a non-professional since the only steps required are the formation of a pilot hole in the air duct and the application of sealant around the misting nozzle once it is inserted through the pilot hole and in the desired position of use. The present invention can also be safely operated and maintained by a non-professional since routine maintenance is often as simple as the exchange of an empty non-pressurized fluid reservoir for a full one, and occasional adjustments to the programmable timer that may be needed when the present invention is used for a new application. The misting nozzles would preferably be made from stainless steel wrapped in brass so that they would never clog and never wear out, to assist in keeping operator maintenance to a minimum. Also, all of the electrical components within the sanitizing system control unit housing operate on 24-volt power, reducing the risk of shock hazard to any operator needing to open the housing cover and work within the interior of the housing. Safety features of the present invention also include fluid carrying tubing that has a pressure rating approximately three times that used during routine operation to prevent tubing failure in places inconvenient for access by non-professional maintenance personnel, a pump that safely operates wet or dry to guard against pump failure due to operator error in anticipating the need for reservoir refill or exchange, and the pump having a fluid recycle loop to prevent pump failure and/or operator injury in the event that the pump discharge opening should become blocked or otherwise inoperative. Further, the amount of operator maintenance is also reduced by the fully automated programmable timer of the present invention having a power loss backup, so that reprogramming of the timer is not required every time the electricity fails for a short period of time. Also, ease of manufacture and operator convenience are enhanced when the electrical components in the system control unit housing of the present invention are attached to a mounting board secured within the housing by a minimum number of fasteners. Optional use of a planar polyvinyl chloride (PVC) mounting board for electrical components that is removable from the housing not only facilitates manufacture by making it easier for the person assembling the present invention to attach the wiring between electrical components, it also facilitates servicing and replacement of electrical components since the mounting board is easily releasable from the installed housing. Since the present invention uses a plurality of nozzles that produce a mist with droplets having a maximum diameter dimension of approximately 250μ, and also has a fan relay that by-passes the air conditioning or heating system thermostat for prompt activation of the fan in the air conditioning or heating system associated with the present invention when the fan is not already in an operational mode so that the fan can be used for more thorough and even dispersal of the mist within the main plenum and attached air ducts, the present invention would be expected to have consistent, reliable, user-friendly, and efficient operation. 
     The description herein provides the preferred embodiments of the present invention but should not be construed as limiting the scope of the present air duct sanitizing invention. For example, variations may occur in the overall size of the system control unit housing as long as it remains large enough to contain all of the needed electrical components while also being sufficiently compact for easy installation and efficient use; the size of the optional mounting board for electrical components as long as it can be easily and releasably secured against the back interior wall of the housing; the size and configuration of the fluid reservoir as long as it retains an upper ridge necessary for its support within the keyhole opening through the bottom of the system control unit housing and contains an ample supply of sanitizing fluid to prevent excessive reservoir exchange; the type of material used to construct the housing and its cover as long as they remain lightweight and easily portable; the type of fastening means used between the housing and the cover; the size and type of material used for the fluid pick-up hose which connects the pump to the fluid reservoir; the number of misting nozzles connected to the pump by fluid carrying tubing; the number of misting nozzles connected to each air duct; the configuration and relative positions of the electrical components to one another within the interior of the system control unit housing; the mounting means used for fixing the electrical components securely in their usable positions within the system control unit housing; and the complement of programming features offered by the programmable timer; in addition to other obvious variations not shown or specifically described herein that are also considered without specific reference to be a part of the present invention. Thus, the scope of the present invention should be determined by the appended claims and their legal equivalents, and not limited to the examples given. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front view of a first preferred embodiment for the system control unit of the present sanitizing system invention, having a compact, portable housing supporting and protecting an electric pump with a barbed hose connection and an attached fluid intake hose, a rectifier, a recycle timer, a programmable timer, and a fan relay electrically wired to cause the pump to periodically draw fluid through the pick-up hose and propel it through the fluid carrying tubing poised for attachment to the barbed hose connection where it ultimately would be emitted from misting nozzles positioned within the branching ends of the fluid carrying tubing that have been inserted through the walls of air ducts, as well as the main plenum to which the ducts are connected, for sanitization purposes to kill molds, mildew, viruses, bacteria, fungi, yeast, algae, and other contaminants within the main plenum and air ducts and maintain them in a sanitized condition. 
     FIG. 2 is a perspective view of the preferred embodiment of the present invention connected to the main plenum, air handler, and air ducts of an air conditioning and heating system in a residential building. 
     FIG. 3 is an enlarged front view of a preferred embodiment of the fluid reservoir used with the present invention, which has an upper ridge through which it is removably supported during use through a keyhole opening by the bottom wall of the system control unit housing. 
     FIG. 4 is an enlarged side view of a preferred embodiment of one of the misting nozzles used with the present invention having a fine mist being discharged therefrom. 
     FIG. 5 is a front view of a second preferred embodiment for the system control unit of the present sanitizing system invention having an evaporation prevention cap and wherein its electrical components are attached to a removable planar mounting board that is attached to the inside back wall of the system control unit housing by a minimum number of readily releasable fasteners. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIGS. 1-5 show the preferred embodiment of an air duct sanitizing system that is sufficiently simple in design to allow a non-professional (not shown) to install and maintain it for a variety of routine uses. FIGS. 1 and 5 show the electrical components of two different preferred embodiments each housed in a pre-assembled system control unit  2 , with the electrical components in FIG. 5 being attached to a mounting board removably fixed within the housing  4 . FIG. 2 shows system control unit  2  installed on the wall of a garage  50  in a residential building  44 , with fluid carrying tubing  8  connecting system control unit  2  to the air ducts  42  and main plenum  46  above garage  50 . FIG. 3 shows a preferred embodiment of the non-pressurized refillable fluid reservoir  34  used for storing an available supply of sanitizing agent (not shown) and which is removably supported by the bottom wall  58  of housing  4 . FIG. 4 shows a preferred embodiment of one of the misting nozzles  64  used with the present invention, each of which is secured within the distal end of one of the branched segments of fluid carrying tubing  8  and inserted either within the main plenum  46  or within the proximal end of one of the air ducts  42  connected to main plenum  46 . The fine mist  66  generated by the misting nozzles  64  is evenly dispersed within main plenum  46  and air ducts  42  to coat their interior surfaces to kill bacteria, viruses, yeast, fungi, algae, molds, and mildew over a period of time and thereafter maintain the interior walls of air ducts  42  and main plenum  46  in a sanitized condition. The fan (not shown) of the associated air conditioning or heating system assists in the dispersal of mist  66 , and is activated by fan relay  28  if the fan is not already in an operational mode when the pump begins operation. Although FIG. 2 shows the present invention having only one system control unit  2  in association with residential building  44 , should residential building  44  be sufficiently large to need more than one air conditioning or heating zone to control airflow, it is contemplated that additional system control units  2  would be used, with one system control unit  2  and its connected fluid carrying tubing  8  being associated with each zone. Further, use of the present invention is not restricted to residential buildings  44 , and although not shown it is considered within the scope of this invention for system control units  2  and fluid carrying tubing  8  to be used with the air conditioning and heating systems in both large and small commercial buildings. 
     FIG. 1 shows system control unit  2  having a rectangular housing  4  vertically positioned so that its opposed longer walls  58  are vertically oriented and become side walls, and its opposed shorter walls  58  form the top and bottom walls of housing  4 . Such orientation, although preferred, is not critical. FIG. 1 shows two substantially round openings  12  through the top wall  58 , one for use in extending fluid carrying tubing  8  upwardly beyond housing  4 , and the other for use in extending electrical wire  14  upwardly beyond housing  4 . The round configuration of openings  12  is preferred but not critical. Further, FIG. 1 shows a keyhole opening  52  through the bottom wall  58  of housing  4 , for use in inserting and supporting non-pressurized fluid reservoir  34  during use. As can be seen in FIG. 3, fluid reservoir  34  has a upper ridge  60  that permits fluid reservoir  34  to become suspended within the narrow portion of keyhole opening  52 , while the wide portion of keyhole opening  52  allows for easy insertion and removal of the upper ridge  60  through the bottom wall  58  of housing  4 . The weight of the liquid sanitizing agent (not shown) within fluid reservoir  34  helps to maintain fluid reservoir  34  securely within the narrow portion of keyhole opening  52  during use. Also, the narrow portion of keyhole opening  52  should have a sufficiently large width dimension to allow easy sliding of fluid reservoir  34  back and forth between the narrow and wide portions of keyhole opening  52 . However, the narrow portion of keyhole opening  52  should not have a width dimension that is excessively large relative to the part of fluid reservoir  34  immediately below upper ridge  60  which could allow fluid reservoir  34  to move in response to operational vibration or casual contact toward the wide portion of keyhole opening  52  where it would no longer be properly supported by the bottom wall  58  of housing  4  and potentially in a position to provide less than optimal access by fluid pick-up hose  10  to the sanitizing agent (not shown) within fluid reservoir  34 . 
     In addition to walls  58 , FIG. 1 shows housing  4  having an interior back surface  56  and a flange  54  outwardly depending from the front perimeter of walls  58 . Although hidden in FIG. 1 by flange  54  and walls  58 , it is contemplated for walls  58  to forwardly depend from the perimeter of interior back surface  56 . FIG. 1 further shows flange  54  having four spaced-apart rectangular apertures  6 , with one rectangular aperture  6  positioned near to each corner of rectangular housing  4  and also positioned adjacent to one of the longer walls  58 . It is contemplated for rectangular apertures  6  to be used in providing a snap-fit connection between housing  4  and a cover  36 , shown in FIG. 2, that seals tightly against flange  54  to protect the interior of housing  4  from unwanted dirt, dust, debris, and incidental contact. Although not shown, it is contemplated for cover  36  to have a flange similar to flange  54  with four protrusions complementary in configuration for snap-fitting securely into rectangular apertures  6 , with each protrusion situated in a position directly opposed to a different one of the rectangular apertures  6 . It is contemplated that the snap-fit connection between the rectangular apertures  6  on flange  54  and the opposing protrusions on cover  36  would provide a close connection therebetween, however it should not be so tight as to make it difficult for the person maintaining the present invention to remove cover  36  when service access to the interior of housing  4  is required. It is not contemplated for the removal of cover  36  to be required for the routine change-out and/or refill of fluid reservoirs  34  as they are independently removable through keyhole opening  52 . Further, the rectangular configuration of openings  6  is not critical, and they could be round, hexagonal, diamond-shaped or have any other configuration that would allow secure attachment of cover  36  to housing  4 . Although not shown, a hinged connection between cover  36  and housing  4  is also considered to within the scope of the present invention, as well as a locking connection between cover  36  and housing  4 , or for cover  36  and housing  4  to have a configuration usable with keyed lock, combination lock, or other type of locking device, so that when the present invention is used in commercial buildings, apartment complexes, or other public places, access to the electrical components within housing  4  can optionally be restricted. 
     FIG. 1 shows housing  4  supporting and protecting an electrical pump  16 , a rectifier  24 , a recycle timer  20 , a fully automated programmable timer  26  with built-in power loss backup, and a fan relay  28 . All are directly mounted to the interior back surface  56  of housing  4  and are contemplated for use with 24-volt electrical current. FIG. 1 shows mounting bolts  18  connecting electrical pump  16  to interior back surface  56 . Although not shown, when mounting bolts  18  are used, it is also preferred for locking nuts with nylon inserts to be used in securing mounting bolts  18  in place as an anti-vibration precaution. Rubber mounting pads (not shown) could also be positioned between electrical pump  16  and housing  4  as a further anti-vibration precaution. In addition, although the means for attachment to housing  4  is not shown in FIG. 1 for clarity of illustration, and is not critical to the present invention, it is contemplated in the preferred embodiment that rectifier  24 , recycle timer  20 , programmable timer  26 , and fan relay  28  be secured in a fixed position to the plastic interior back surface  56  of housing  4  with a plurality of nuts and mounting bolts  18 . FIG. 1 also shows wiring  30  electrically connecting electrical pump  16  to rectifier  24 ; rectifier  24  to recycle timer  20 ; recycle timer  20  to programmable timer  26  and fan relay  28 ; and programmable timer  26  to fan relay  28 . Although not limited thereto, in the preferred embodiment shown in FIG. 1, wiring  30  would comprise 16-gauge copper wire. FIG. 1 further shows the end of an electrical wire  14  poised for connection to both the programmable timer  26  and the fan relay  28 . Although not shown in FIG. 1, but shown in FIG. 2, the other end of electrical wire  14  would be connected to the air handler  38  of the air conditioning and heating system with which the present invention is associated so that the present invention can draw 24-volt power therefrom for its operation. As a result, no electrical current higher than 24 volts would be connected to housing  4 , making the present invention safer for use by non-professional maintenance personnel (not shown). 
     FIG. 1 also shows electrical pump  16  being connected to a fluid pick-up hose  10  that extends downwardly beyond housing  4  through keyhole opening  52 . Fluid pick-up hose  10  is made from flexible tubing material, as shown by its angled configuration in FIG.  1 . It is critical that fluid pick-up hose  10  have a length dimension that extends to the bottom of the size of fluid reservoir  34  contemplated for use when it is in a usable position supported by housing  4  through the narrow portion of keyhole opening  52 . Also, in the preferred embodiment it is preferred that the outside diameter of fluid pick-up hose  10  be close in dimension to the diameter of top opening  62  in fluid reservoir  34 , shown in FIG.  3 . However, if the outside diameter of fluid pick-up hose  10  were significantly smaller than the diameter dimension of top opening  62 , evaporation of the sanitizing or other liquid stored within fluid reservoir  34  would be likely to occur. To prevent such evaporation, a cap, such as number  70  in FIG. 5, adapted in configuration to closely fit over and/or around top opening  62  can be optionally be mounted on fluid pick-up hose  10  to remain in a position ready for use with a newly refilled or replacement fluid reservoir  34 , and an operator would not be required to separately handle such a cap  70 , thus keeping operator maintenance simple and minimal. To accommodate fluid reservoirs  34  having different fluid holding capacities, the evaporation preventing cap  70  optionally mounted on fluid pick-up hose  10  could be made minimally slidable along fluid pick-up hose  10  so that it could always be adjusted for optimal positioning over the top opening  62  of every size of fluid reservoir  34  contemplated for use. In a position opposed to fluid pick-up hose  10  and also connected to electrical pump  16 , FIG. 1 shows a barbed hose fitting  48  with the one end of a fluid carrying tubing  8  poised for connection thereto. FIG. 1 shows the outer surface of barbed hose fitting  48  having a ribbed configuration that allows fluid carrying tubing  8  to be securely connected to barbed hose fitting  48  without the use of clamps or other fastening devices (not shown). 
     Although a rectangular configuration is preferred for housing  4 , it is not critical and housing  4  could also have different configurations including those that are substantially round, oval, or hexagonal, and still be able to effectively perform its support and protective functions, as long as the portion of bottom wall  58  used for the positioning of keyhole opening  52  is sufficiently horizontal in orientation so that fluid reservoir  34  remains securely in place within the narrow portion of keyhole opening  52  during use. Also, and although not critical, in the preferred embodiment it is contemplated for housing  4  to be made from polyethylene for easy maintenance and to have approximate height, width, and depth dimensions respectively of fifteen inches, thirteen inches, and six inches. The lightweight material from which it is made, and its compact size, would make housing  4  readily portable and easily mounted by a non-professional installer to a variety of mounting surfaces (not shown). Since electrical pump  16  is the component positioned within housing  4  with the greatest depth dimension, at a minimum housing  4  must have a depth dimension sufficient for containment of electrical pump  16  while simultaneously allowing adequate room for secure connection of cover  36 . Further, the sizes of rectifier  24 , recycle timer  20 , programmable timer  26 , and fan relay  28  relative to one another is not critical, nor is the positioning of rectifier  24 , recycle timer  20 , programmable timer  26 , and fan relay  28  relative to one another within housing  4 , as long as the amount of wiring  30  needed for electrical connection therebetween is not significantly increased. 
     In the most preferred embodiment of the present invention, recycle timer  20  would operate on 24-volt alternating current and cause activation of electrical pump  16 . The preferred recycle timer  20  would have a first cycle set to for a period of approximately thirty seconds, with a second cycle that is adjustable between one and thirty seconds. Recycle timer  20  would also have a control  22  for adjusting the duration of the second cycle. The longer the run cycle of electrical pump  16 , the more sanitizing agent (not shown) or other liquid in fluid reservoir  34  is drawn through pump  16  and forced through misting nozzles  64 . Fan relay  28  would also operate on 24-volt alternating current, and as shown in FIG. 1 by the symbol marked between the two centrally positioned terminals, its circuitry would normally be in an open position. Once electricity is directed to fan relay  28 , the circuit would close to cause by-passing of a thermostat in the air conditioning or heating system with which the present invention is associated when the fan is not in an operating made at the beginning of pump operation. The resulting activation of the air conditioning or heating system fan would then create even dispersal within the main plenum  46  and air ducts  42 , shown in FIG. 2, of the 250μ or smaller droplets in the mist  66  formed by misting nozzles  64  positioned at the distal ends of various branched segments of fluid carrying tubing  8 . Programmable timer  26  would operate on 24-volt alternating current, however, it would have a backup provision for power loss protection so that reprogramming is not necessary every time the power drawn from the associated air conditioning or heating system fails for a short period of time. The preferred programmable timer  26  would also have a capacitor power loss backup, an internal clock (not shown), a by-pass mode, a control for instantaneous system activation, and a digital display  32  for programming assistance. Since it is contemplated that electrical pump  16  would operate on 24-volt direct current instead of 24-volt alternating current, it is contemplated for electrical pump  16  to be connected to a full bridge rectifier  24  that changes 24-volt alternating current into 24-volt direct current. Further, electrical pump  16  would operate to force sanitizing, air purification, or aromatherapy liquid (not shown) into fluid carrying tubing  8  at approximately 60 psi, have the ability to operate safely even though no liquid is available in fluid reservoir  34 , and have an internal by-pass loop for pumped liquid should the discharge opening within barbed hose connection  48  in electrical pump  16  become blocked or inoperative for any reason. Further, misting nozzles  64  would be made from stainless steel encased in brass so that they would never become clogged and never wear out, another feature incorporated into the present invention to reduce operator maintenance and expense. 
     FIG. 5 shows a second preferred embodiment of system control unit  2 , similar to FIG. 1, with the addition of a planar mounting board  68  to which all electrical components within housing  4  are attached and an evaporation prevention cap  70  attached to fluid pick-up hose  10 . FIG. 5 also shows two inverted mounting bolts  18  used for readily releasable attachment of mounting board  68  to the interior back surface  56  of housing  4 . The size of mounting board  68  is not critical as long as all electrical components selected for placement within housing  4  can be attached thereto without overcrowding. Therefore, the perimeter dimension of mounting board  68  may be only slightly smaller than the perimeter dimension of the back surface of housing  4 , or the perimeter dimension of mounting board  68  may be substantially less than the perimeter dimension of the back surface of housing  4 , as shown in FIG.  5 . Also, the mounting bolts  18  used to affix mounting board  58  to interior back surface  56  are inverted so that mounting board  58  can be removed from housing  4  without detaching housing  4  from its support surface (not shown). Since the nuts securing mounting bolts  18  are positioned within housing  4 , they are readily accessible for prompt counter-rotation and removal from mounting inverted mounting bolts  18 , paving the way for subsequent separation of mounting board  58  from inverted mounting bolts  18  and ultimate disconnection from housing  4 . The configuration of nut used to secure mounting bolts  18  in place is not critical as long as the nuts are readily releasable from mounting bolts  18 . Although not illustrated, since winged nuts are easily and readily hand-manipulated, they are also considered within the scope of the present invention for such purpose. While the number of inverted mounting bolts  18  is not critical, a small number is contemplated, and two such inverted mounting bolts  18  are considered adequate for most purposes. 
     FIG. 2 shows system control unit  2  mounted on the wall of a garage  50  in a residential building  44 . In such a position, system control unit  2  is conveniently located for easy maintenance access. Should more than one system control unit  2  be used in residential building  44  to service different air circulation zones, the multiple system control units  2  can be consolidated in location for efficient operator maintenance, or easily mounted apart from one another depending upon the space available or other such need. FIG. 2 shows the lower part of fluid reservoir  34  extending below the bottom wall  58  of system control unit  2 , with fluid reservoir  34  illustrated as being connected to and supported by system control unit  2 . FIG. 2 also shows cover  36  separated from system control unit  2  and leaning against a wall in garage  50  in an out-of-the-way position until it is again needed for use in protecting the interior of system control unit  2  from unwanted dust, dirt, debris, and inadvertent contact. The air conditioning and heating system servicing residential building  44  sits above garage  50  and is shown to include main plenum  46 , air handler  38  positioned adjacent to main plenum  46 , and five air ducts  42  each connected on one of its ends to main plenum  46 . The arrows in FIG. 2, which extend beyond each air duct  42 , show the direction of airflow within air ducts  42 . FIG. 2 further shows an electrical wire  14  extending upwardly beyond the upper wall  58  of system control unit  2  and being connected on its upper end to air handler  38 . It is through electrical wire  14  that the present invention obtains the reduced voltage current needed to operate electrical pump  16 , rectifier  24 , recycle timer  20 , programmable timer  26 , and fan relay  28 , and enhance operator safety. Fluid carrying tubing  8  also extends upwardly beyond the upper wall  58  of system control unit  2  where through the use of several T-shaped barbed hose connectors  40  it becomes a branched array that provides fluid communication between system control unit  2  and main plenum  46 , as well as each air duct  42  connected to main plenum  46 . The multiple connections of fluid carrying tubing  8  into all of the air ducts  42  connected to main plenum  46  provides for more even distribution of the sanitizing agent mist, shown in FIG. 4 by the number  66 , within air ducts  42  so that air ducts  42  remain in a sanitized condition once the initial treatment period of approximately 30 days is complete. Connection of fluid carrying tubing  8  to each air duct  42  is easily accomplished. A pilot hole (not shown) is made into each air duct  42  close to main plenum  46 . Thereafter, sealant (not shown) is used to secure each branching segment of fluid carrying tubing  8  within a different one of the pilot holes made. Although not generally required, it is considered within the scope of the present invention for more than one misting nozzle  64  and segment of fluid carrying tubing  8  to be connected to each available air duct  42 . Thus the present invention can be effectively used in new construction, as well as easily provide unlimited retrofit capability to different types of existing air conditioning and heating systems. The size, type, location, and orientation of main plenum  46 , air handler  38 , and air ducts  42  are not an impediment to connection and use of the present invention therewith. Thus even when the main plenum  46  is oriented in a horizontal position in an attic, or in a vertical position within a garage or a closet, use of the present invention is easily accomplished. 
     FIG. 3 shows a preferred embodiment of fluid reservoir  34 , which can be used to store an available quantity of liquid air duct sanitizing agent (not shown), or in the alternative air purification and aromatherapy fluids. Fluid reservoir  34  is not pressurized and although not clearly shown in FIG. 3, it has a top opening  62  through which fluid pick-up hose  10  is inserted during use. The size and configuration of fluid reservoir  34  are not critical, although the quantity of sanitizing fluid (not shown) made available must be adequate to keep operator maintenance to a minimum. Only a small amount of sanitizing fluid is drawn from fluid reservoir  34  during each cycle of electric pump  16 . Therefore, even if electric pump  16  is activated six times in a day, a fluid reservoir  34  having a quart capacity would be adequate for most uses. Although not shown and not limited thereto, the preferred chemical used with the present invention for air duct sanitizing purposes is chlorine dioxide, which is approved by the U.S. Environmental Protection Agency for such use. It has a low toxicity, a category III EPA safety rating, and kills bacteria, viruses, fungi, yeast, algae, molds, and mildew. Also, there is no special handling or disposal required for empty fluid reservoirs  34  which are discarded or recycled. Further, chlorine dioxide provides point-of-contact microbial control and there is no activation or rinsing required. For air purification purposes, a chemical such as OXINE can be used, however buildings so treated must be unoccupied. Once a building requiring air purification treatment has been vacated, a quart of appropriate chemical will be added to reservoir  34 . Programmable timer  26  will be set to allow electrical pump  16  to run continuously for a period of approximately one hour, after which occupants will be allowed to return to the treated building following an additional cure period of approximately one hour to allow the chemical to dissipate to safe levels. Although not shown, aromatherapy can be accomplished by either adding a pleasing scent to air sanitizing chemicals, or independently placing aromatherapy solutions in fluid reservoir  34  and adjusting progranmmable timer  26  to distribute appropriate quantities of the aromatherapy chemicals into the building atmosphere to achieve a pleasing effect. It is critical that the fluid pick-up hose  10  for insertion within top opening  62  in fluid reservoir  34  has a length dimension that extends to the bottom of the largest size of fluid reservoir  34  contemplated for use, when it is in its usable position supported by housing  4  through the narrow portion of keyhole opening  52 , so that the full amount of sanitizing agent or other liquid stored in fluid reservoir  34  is available for use. Also, in the preferred embodiment it is preferred that the outside diameter of fluid pick-up hose  10  be close in dimension to the diameter of top opening  62  in fluid reservoir  34  to prevent evaporation of the sanitizing agent or other liquid stored within fluid reservoir  34 . If the diameter dimension of fluid pick-up hose  10  is significantly smaller than the diameter of top opening  62 , an evaporation-preventing cap (not shown) should be used that is adapted in configuration to closely fit over and/or around top opening  62 . To keep operator maintenance simple and minimal, such a cap can be mounted on fluid pick-up hose  10  so that it would remain in a position ready for use with a newly refilled or replacement fluid reservoir  34 . Also, to accommodate reservoirs  34  having different fluid holding capacities, the evaporation-preventing cap mounted on fluid pick-up hose  10  could be optionally made minimally slidable along fluid pick-up hose  10  so that it could always be adjusted for optimal positioning over the top opening  62  of every size of fluid reservoir  34  used. 
     FIG. 4 is an enlarged side view of a preferred embodiment of one of the misting nozzles  64  used with the present invention for emitting a fine mist  66  of sanitizing, air purification, or aromatherapy chemicals. The exact configuration of misting nozzle  64  is not critical, and it is considered within the scope of the present invention to have misting nozzles  64  which have other sizes and shapes as long as they are relatively lightweight and capable of producing a fine mist of droplets having a maximum diameter of approximately 250μ. It is contemplated that each misting nozzle  64  used with the present invention be made from stainless steel wrapped in brass to minimize maintenance cost since it would resist clogging and never wear out. Also, although not shown, a hose fitting connection can be used to securely attach each misting nozzle  64  into the end of one branching segment of fluid carrying tubing  8  so that the misting nozzle  64  can be readily seated within an air duct  42  to spray a fine mist  66  of droplets having a maximum diameter dimension of approximately 250μ to kill undesired organisms within the interior of air duct  42 , such as bacteria, viruses, algae, fungi, yeast, molds, and mildew. 
     To use the present invention an operator (not shown) would assemble one segment of 200 psi rated fluid carrying tubing  8  to other similar segments with T-shaped barbed hose connections  40  to form a branched array of fluid carrying tubing  8 . One such segment would be provided for each misting nozzle  64  needed for use. The trunk line of the branching array would be connected to the barbed hose fitting  48  surrounding the discharge opening of electrical pump  16 . Each misting nozzle  64  would be secured within one of the ends of a different one of the fluid carrying tubing  8  segments. Although one misting nozzle  64  is usually adequate to sanitize an air duct  42 , it is considered within the scope of the present invention for more than one misting nozzle  64  to be used in an air duct  42 . Therefore, at least one pilot hole (not shown) would be formed through each air duct  42  targeted for sanitization and one or more pilot holes would be formed through the main plenum  46  to which the air ducts  42  are attached. The pilot holes in the air ducts  42  would be located near to main plenum  46 . After the pilot holes are made, a quantity of sealant (not shown) is used to secure each misting nozzle  64  within the main plenum or a different one of the air ducts  42  so that each pilot hole is filled with a misting nozzle  64  secured within a segment of fluid carrying tubing  8 . The system control unit  2  of the present invention would be mounted within the building targeted for sanitization, such as residential building  44 , in a place easily accessible for operator maintenance. Preferably, once system control unit  2  is secured into its usable position, an electrical wire  14  would be connected between the air handler  38  of the air conditioning or heating system with which the present invention is associated and programmable timer  26 , as well as fan relay  28 . A fluid reservoir  34  with the type and quantity of sanitizing, air purification, or aromatherapy liquid appropriate to the intended application would then be selected and connected to system control unit  2  by inserting fluid pick-up hose  10  through top opening  62  in fluid reservoir  34 , and also inserting fluid reservoir  34  through the larger portion of keyhole opening  52  in bottom wall  58  of housing  4  and sliding fluid reservoir  34  into the narrow portion of keyhole opening  52  to lock fluid reservoir  34  into its usable position with upper ridge  60  supported by the inside surface of bottom wall  58 . To exchange an empty fluid reservoir  34  for a full one, or to refill it, the operator would not have to remove cover  36  from housing  4 , and instead only need to slide fluid reservoir  34  from the narrow portion of keyhole opening  52  toward the larger portion of keyhole opening  52 , followed by the application of a downward force to the bottom part of fluid reservoir  34  sufficient to cause upper ridge  60  and top opening  62  to become withdrawn from the larger portion of keyhole opening  52 . Safety features for the operator (not shown) include the high-pressure fluid carrying tubing  8  rated three times that encountered during normal operation of electrical pump  16 , the reduced voltage programmable timer  26  and electrical pump  16  to reduce the potential risk of fire and operator injury since fluid and electricity are used together within housing  4 , an electrical pump  16  that safely operates wet or dry should the operator fail to anticipate timely replacement or refill of fluid reservoir  34  before all of the liquid (not shown) therein is completely used, and the non-pressurized supply of sanitizing agent or other liquid provided for use. The present invention is also user-friendly in many ways. Housing  4  can be mounted anywhere that is convenient for maintenance access, and it is not needed to position housing  4  close to the main plenum  46 , any air duct  42 , or an electrical outlet (not shown). Also, it is contemplated for housing  4  to be made from plastic materials that are essentially maintenance-free and resistant to deterioration by the corrosive chemicals sometimes used for air sanitization. The plastic material also makes housing  4  lightweight and easily portable during installation. In addition, cover  36  is designed for easy separation from housing  4  when operator entry into the interior of housing  4  is required. Also, the optional use of a mounting board  68  to attach electrical pump  16 , programmable timer  26 , fan relay  28 , rectifier  24 , and recycle timer  20  to housing  4  facilitates manufacture and benefits the owner and/or operator by allowing the removal only of the mounting board  68 , and not the entire housing  4 , for assessment of maintenance needs in the event of component failure. Further, the type, orientation, and location of main plenum  46  have no adverse impact on the installation of the present invention, as the present invention is simple in design and widely adaptable for retrofitting to existing air conditioning and heating systems.