Patent Publication Number: US-7914604-B2

Title: Air conditioning system with modular electrically stimulated air filter apparatus

Description:
This application is a division of application Ser. No. 12/049,095, filed on Mar. 14, 2008, now U.S. Pat. No. 7,608,135, which is a division of application Ser. No. 11/828,245, filed on Jul. 25, 2007, now U.S. Pat. No. 7,531,028. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to air conditioning systems and, more particularly, to air conditioning systems incorporating electrically stimulated air filter apparatus, and to a method for retrofitting an air conditioning system with electrically stimulated air filter apparatus. 
     BACKGROUND OF THE INVENTION 
     Airborne particles can be removed from a polluted air stream by a variety of physical processes. Common types of equipment for collecting fine particulates include, for example, cyclones, scrubbers, electrostatic precipitators, and baghouse filters. 
     Most air-pollution control projects are unique. Accordingly, the type of particle collection device, or combination of devices, to be employed normally must be carefully chosen in each implementation on a case-by-case basis. Important particulate characteristics that influence the selection of collection devices include corrosivity, reactivity, shape, density, and size and size distribution including the range of different particle sizes in the air stream. Other design factors include air stream characteristics (e.g., pressure, temperature, and viscosity), flow rate, removal efficiency requirements, and allowable resistance to airflow. In general, cyclone collectors are often used to control industrial dust emissions and as precleaners for other collection devices. Wet scrubbers are usually applied in the control of flammable or explosive dusts or mists from such sources as industrial and chemical processing facilities and hazardous-waste incinerators; they can handle hot air streams and sticky particles. Large scale electrostatic precipitators or filtration devices and fabric-filter baghouses are often used at power plants. 
     Electrostatic precipitation or filtration, which are interchangeable terms, is a commonly used method for removing fine particulates from air streams. In an electrostatic precipitator, an electric charge is imparted to particles suspended in an air stream, which are then removed by the influence of an electric field. A typical precipitation unit or device includes baffles for distributing airflow, discharge and collection electrodes, a dust clean-out system, and collection hoppers. A high DC voltage, often as much as 100,000 volts in large scale applications, is applied to the discharge electrodes to charge the particles, which then are attracted to oppositely charged collection electrodes on which they become trapped. 
     In a typical large-scale electrostatic precipitator the collection electrodes consists of a group of large rectangular metal plates suspended vertically and parallel to each other inside a boxlike structure. There are often hundreds of plates having a combined surface area of tens of thousands of square meters. Rows of discharge electrode wires hang between the collection plates. The wires are given a negative electric charge, whereas the plates are grounded and thus become positively charged. 
     Particles that stick to the collection plates are removed periodically when the plates are shaken, or “rapped.” Rapping is a mechanical technique for separating the trapped particles from the plates, which typically become covered with a 6-mm (0.2-inch) layer of dust. Rappers are either of the impulse (single-blow) or vibrating type. The dislodged particles are collected in a hopper at the bottom of the unit and removed for disposal. An electrostatic precipitator can remove exceptionally small particulates on the order of 1 micrometer (0.00004 inch) with an efficiency exceeding 99 percent. The effectiveness of electrostatic precipitators in removing fly ash from the combustion gases of fossil-fuel furnaces accounts for their high frequency of use at power stations. 
     Large-scale electrostatic precipitators are expensive, difficult to build, and quite large. However, electrostatic filtration is exceedingly efficient and highly reliable. As a result, skilled artisans have devoted considerable effort and resources toward the development of small-scale electrostatic precipitators or air filtration devices specifically adapted for small scale applications, such as for filtering breathing. Although considerable attention has been directed toward the development of small-scale and portable electrostatic filtration devices utilized principally to filter breathing air, existing implementations are difficult to construct, expensive, must be constructed to strict and often unattainable tolerances, cannot be tuned or calibrated as needed to meet specific and/or changing environmental conditions or air filtering requirements, and are not suitable for use in large-scale applications, such as in conjunction with large-scale air conditioning systems utilized in large building establishments, such as casinos, office buildings, hospitals, and schools. Given these and other deficiencies in the art of electrostatic air filters, the need for continued improvement is evident. 
     SUMMARY OF THE INVENTION 
     According to the invention, an air conditioning system includes a housing, an air flow pathway extending through the housing from an inlet to an outlet, and air conditioning apparatus disposed in the airflow pathway between the inlet and the outlet conditioning an air stream passing through the air flow pathway from the inlet to the outlet. A first framework is mounted in the airflow pathway between the conditioning air apparatus and the inlet, and a second framework is mounted in the airflow pathway between the first framework and the inlet. The first framework carries filters each for entrapping contaminants in the air stream upstream of the conditioning air apparatus. The filters cooperate forming an upstream face facing the second framework and an opposed downstream face facing the conditioning air apparatus. Downstream electrodes are disposed in the air flow pathway between the air conditioning apparatus and the filters. Each downstream electrode is affixed to and contacts one of the filters. Electrical contacts mounted to the first framework electrically interconnect the downstream electrodes, according to the principle of the invention. An ionizer electrode is carried by the first framework in the air flow pathway between the inlet and the upstream face formed by the filters, and an upstream electrode is carried by the first framework in the air flow pathway between the inlet and the ionizer electrode. A first potential applied to the ionizer electrode imparts through induction a) a second potential to the upstream electrode forming a first ionizing field between the upstream electrode and the ionizer electrode, and b) a third potential to the downstream electrodes. The electrical contacts electrically interconnecting the downstream electrodes substantially uniformly disperse the third potential across the downstream electrodes forming a substantially uniform second ionizing field between the downstream electrodes and the ionizer electrode. The filters each have a front face and a rear face. The front faces cooperate to form the upstream face of the filters and the rear faces cooperating forming the downstream face of the filters. An abutment mounted to the first framework acts on the front faces of the filters thereby urging the downstream electrodes against the electrical contacts. The abutment consists of an elongate rod mounted to the first framework. Slots are formed in the first framework, and the elongate rod is received in, and held by, the slots. In a particular embodiment, the elongate rod has opposed first and second ends and a length extending between the first and second ends acting on the front faces of the filters, and the elongate rod defining a longitudinal axis extending front the first end to the second end. Structure is provided between the elongate rod and the first framework preventing movement of the elongate rod relative to the first framework along the longitudinal axis of the elongate rod. The structure interacting between the elongate rod and the first framework includes stops interacting between the elongate rod and the first framework. The stops are preferably carried by the elongate rod and, in particular, one of the stops by the first end of the elongate rod and another of the stops by the second end of the elongate rod. The ionizer electrode includes an ionizing wire having a length and opposed first and second ends secured to the second framework, in which the length of the ionizing wire between the first and second ends is strung across the second framework forming a planar array of courses of the length of the ionizing wire parallel to the upstream electrode and the downstream electrodes. The length of the ionizing wire between the first and second ends is strung across pins affixed to the second framework. Tension is applied to the ionizing wire maintaining tension across each of the courses of the length of the ionizing wire. A tension spring coupled between one of the first and second ends of the ionizing wire and the second framework applies the tension to the ionizing wire. In another embodiment, the tension applied by the ionizing wire is provided by a first tension spring coupled between the first end of the ionizing wire and the second framework, and a second tension spring coupled between the second end of the ionizing wire and the second framework. The upstream electrode is electrically isolated inhibiting arcing from occurring at the upstream electrode, and the downstream electrodes are grounded. A resistor is coupled to the upstream electrode and is adjusted to obtain a predetermined value of the first potential. The filters each consists of a dielectric filter. In a preferred embodiment, opposed, spaced-apart supports are affixed to the housing, and the first and second frameworks are each mounted to, and supported between, the supports. Preferably, the first and second frameworks are each slidably received by the supports, and the second framework is slidably received by the supports. The supports each have opposed first and second ends and a length extending between the opposed ends and define a longitudinal axis extending from the first end to the second end, in which the first and second frameworks are slidably received by the supports in longitudinal directions along the longitudinal axes of the respective supports. Compartments are formed in the first framework, and the filters are each received in one of the compartments. 
     According to the invention, an air conditioning system includes a housing, an air flow pathway extending through the housing from an inlet to an outlet, and air conditioning apparatus disposed in the airflow pathway between the inlet and the outlet conditioning an air stream passing through the air flow pathway from the inlet to the outlet. First and second framework are mounted in the airflow pathway between the conditioning air apparatus and the inlet, and third and fourth frameworks mounted in the airflow pathway between the first and frameworks and the inlet. Filters are carried by the first and second frameworks each for entrapping contaminants in the air stream upstream of the conditioning air apparatus. The filters carried by the first and second frameworks cooperate to form an upstream face facing the second framework and an opposed downstream face facing the conditioning air apparatus. Downstream electrodes are disposed in the air flow pathway between the air conditioning apparatus. The downstream electrodes are each affixed to, and contact, one of the filters. First electrical contacts mounted to the first framework electrically interconnect the downstream electrodes of the filters carried by the first framework, and second electrical contacts mounted to the second framework electrically interconnect the downstream electrodes of the filters carried by the second framework. The first electrical contacts of the first framework are electrically connected to the second electrical contacts of the second framework. A first ionizer electrode is carried by the third framework in the air flow pathway between the inlet and the portion of the upstream face formed by the filters carried by the first framework, and a second ionizer electrode is carried by the fourth framework in the air flow pathway between the inlet and the portion of the upstream face formed by the filters carried by the second framework. The first ionizer electrode is electrically connected to the second ionizer electrode. A first upstream electrode is carried by the third framework in the air flow pathway between the inlet and the first ionizer electrode, and a second upstream electrode is carried by the fourth framework in the air flow pathway between the inlet and the second ionizer electrode. The first upstream electrode is electrically connected to the second upstream electrode. A first potential applied to the first and second ionizer electrodes imparts through induction a) a second potential to the first and second upstream electrodes, and b) a third potential to the downstream electrodes of the filters carried by the first and second frameworks. The electrical connection between the first and second ionizer electrodes substantially uniformly disperses the first potential across the first and second ionizer electrodes thereby forming a substantially uniform first ionizing field between the first and second upstream electrodes and the first and second ionizer electrodes. The first electrical contacts electrically connected to the second electrical contacts interconnecting the downstream electrodes of the filters carried by the first and second frameworks substantially uniformly disperse the third potential across the downstream electrodes forming a substantially uniform second ionizing field between the downstream electrodes of the filters of the first and second frameworks and the first and second ionizer electrodes. The filters carried by the first and second frameworks each have a front face and a rear face, the front faces cooperating to form the upstream face of the filters carried by the first and second frameworks. A first abutment mounted to the first framework acts on the front faces of the filters carried by the first framework thereby urging the downstream electrodes of the filters carried by the first framework against the first electrical contacts. A second abutment mounted to the second framework acts on the front faces of the filters carried by the second framework thereby urging the downstream electrodes of the filters carried by the second framework against the second electrical contacts. The first abutment consists of a first elongate rod mounted to the first framework, and the second abutment consists of a second elongate rod mounted to the second framework. First slots are formed in the first framework, second slots are formed in the second framework, the first elongate rod is received in, and held by, the first slots, and the second elongate rod is received in, and held by, the second slots. The first elongate rod has opposed first and second ends and a length extending between the first and second ends acting on the front faces of the filters carried by the first framework, the first elongate rod defining a first longitudinal axis extending front the first end to the second end. First structure interacting between the first elongate rod and the first framework prevents movement of the first elongate rod relative to the first framework along the first longitudinal axis of the first elongate rod. The first structure interacting between the first elongate rod and the first framework includes first stops interacting between the first elongate rod and the first framework. The first stops are carried by the first elongate rod and, in particular, by the first and second ends, respectively, of the first elongate rod. The second elongate rod has opposed third and fourth ends and a length extending between the third and fourth ends acting on the front faces of the filters carried by the second framework, the second elongate rod defining a second longitudinal axis extending front the third end to the fourth end. Second structure interacting between the second elongate rod and the second framework prevents movement of the second elongate rod relative to the second framework along the second longitudinal axis of the second elongate rod. The second structure interacting between the second elongate rod and the second framework comprise second stops interacting between the second elongate rod and the second framework. The second stops are carried by the second elongate rod and, in particular, by the third and fourth ends, respectively, of the second elongate rod. The first ionizer electrode includes a first ionizing wire having a first length and opposed first and second ends secured to the third framework, and the first length of the first ionizing wire between the first and second ends of the first ionizing wire strung across the third framework forming a first planar array of courses of the first length of the first ionizing wire parallel to the first upstream electrode and the downstream electrodes of the filters carried by the first framework. The second ionizer electrode consists of a second ionizing wire having a second length and opposed third and fourth ends secured to the fourth framework, and the second length of the second ionizing wire between the third and fourth ends of the second ionizing wire strung across the fourth framework forming a second planar array of courses of the second length of the second ionizing wire parallel to the second upstream electrode and the downstream electrodes of the filters carried by the second framework. The first length of the first ionizing wire between the first and second ends of the first ionizing wire is strung across first pins affixed to the third framework, and tension applied to the first ionizing wire maintains tension across each of the courses of the first length of the first ionizing wire. A tension spring coupled between one of the first and second ends of the first ionizing wire and the third framework applies the tension to the first ionizing wire. In another embodiment, the tension applied to the first ionizing wire is provided by a first tension spring coupled between the first end of the first ionizing wire and the third framework, and a second tension spring coupled between the second end of the first ionizing wire and the third framework. The second length of the second ionizing wire between the third and fourth ends of the second ionizing wire is strung across second pins affixed to the fourth framework, and tension applied to the second ionizing wire maintains tension across each of the courses of the second length of the second ionizing wire. A tension spring coupled between one of the third and fourth ends of the second ionizing wire and the fourth framework applies the tension to the second ionizing wire. In another embodiment, the tension applied to the second ionizing wire is provided by a first tension spring coupled between the third end of the second ionizing wire and the fourth framework, and a second tension spring coupled between the fourth end of the second ionizing wire and the fourth framework. The first and second upstream electrodes are together electrically isolated inhibiting arcing from occurring at the first and second upstream electrode. The downstream electrodes of the filters carried by the first and second frameworks are grounded. A resistor coupled to the first and second upstream electrodes is adjusted to obtain a predetermined value of the first potential. The filters each consist of a dielectric filter. Third electrical contacts interacting between the first and second frameworks electrically connect the first electrical contacts of the first framework to the second electrical contacts of the second framework, electrically connect the first ionizer electrode to the second ionizer electrode, and electrically connect the first upstream electrode to the second upstream electrode. Opposed, spaced-apart supports are affixed to the housing, and the first, second, third, and fourth frameworks each mounted to, and supported between, the supports. Preferably, the first, second, third, and fourth frameworks are each slidably received by the supports, preferably along the longitudinal axes of the respective supports. First compartments formed in the first framework, and the filters carried by the first framework are each received in one of the first compartments. Second compartments are formed in the second framework, and the filters carried by the second framework each received in one of the second compartments. 
     Consistent with the foregoing summary of preferred embodiments, and the ensuing detailed description, which are to be taken together, the invention also contemplates associated apparatus and method embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring to the drawings: 
         FIG. 1  is a perspective view of a prior art air conditioning system mounted adjacent to a building for providing the interior of the building with conditioning air; 
         FIG. 2  is the air conditioning system illustrated in  FIG. 1  shown as it would appear outfitted with an electrically stimulated air filter apparatus constructed and arranged in accordance with the principle of the invention forming an enhanced air conditioning system for producing clean, conditioned air; 
         FIG. 3  is an enlarged fragmented perspective view of the prior art air conditioning system of  FIG. 1  with a portion of a housing of the air conditioning system shown removed illustrating an air conditioning apparatus disposed in an air flow pathway extending through the housing; 
         FIG. 4  is a view very similar to the view of  FIG. 3  illustrating an electrically stimulated air filter apparatus installed in the air flow pathway upstream of the air conditioning apparatus, the electrically stimulated air filter apparatus constructed and arranged in accordance with the principle of the invention; 
         FIG. 5  is a control system for controlling the operation of the electrically stimulated air filter apparatus of  FIG. 4 ; 
         FIG. 6  is a highly generalized exploded perspective view of the electrically stimulated air filter apparatus of  FIG. 4  illustrating filter assemblies, ionizer assemblies, and supports for securing the filter and ionizer assemblies; 
         FIG. 7  a side elevational view of the electrically stimulated air filter apparatus of  FIG. 6  shown assembled, with portions thereof shown in vertical cross section for illustrative purposes; 
         FIG. 8  is a top plan view of the electrically stimulated air filter apparatus of  FIG. 7 , with portions thereof shown in horizontal cross section for illustrative purposes; 
         FIG. 9  is a fragmented front elevational view of the electrically stimulated air filter apparatus of  FIG. 7 ; 
         FIG. 10  is a side elevational of the electrically stimulated air filter apparatus of  FIG. 7 ; 
         FIG. 11  is a fragmented rear elevational view of the electrically stimulated air filter apparatus of  FIG. 7 ; 
         FIG. 12  is a fragmented rear elevational view of one of the ionizer assemblies of the electrically stimulated air filter apparatus of  FIG. 6 , the ionizer assembly including ionizing wires supported by a framework; 
         FIG. 13  is an enlarged fragmented perspective view of the ionizer assembly of  FIG. 12  illustrating a spring coupled between an end of an ionizing wire and the framework applying tension to the ionizing wire; 
         FIG. 14  is an enlarged fragmented perspective view of one of the ionizer assemblies of  FIG. 6  illustrating an electrical contact or plug operatively coupled to supply wires for imparting a potential across the ionizing wires; 
         FIG. 15  is a rear perspective view of a filter used in conjunction with the electrically stimulated air filter apparatus of  FIG. 6 , the filter including an electrode affixed to, and contacting, a broad pleated body having a shape and a plurality of applied support members extending through the electrode into the broad pleated body for maintaining the shape of the broad pleated body, in which one of the support members shown detached for illustrative purposes; 
         FIG. 16  is a front elevational view of the filter of  FIG. 15 ; 
         FIG. 17  is a side elevational view of the filter of  FIG. 15 ; 
         FIG. 18  is a rear elevational view of the filter of  FIG. 15 ; 
         FIG. 19  is a side elevational view of the filter of  FIG. 15  with portions thereof shown in vertical cross section for illustrative purposes; 
         FIG. 20  is a sectional view taken along line  20 - 20  of  FIG. 15 ; 
         FIG. 21  is an enlarged fragmented perspective view of the filter of  FIG. 15  illustrating one of the support members extending into the broad pleated body through the electrode; 
         FIG. 22  is a sectional view taken along line  22 - 22  of  FIG. 15 ; 
         FIG. 23  is an enlarged front perspective view of the filter of  FIG. 15  shown received by a framework of one of the filter assemblies of the electrically stimulated air filter apparatus of  FIG. 6 , including rods carried by the framework interacting with the filter; 
         FIG. 24  is an enlarged fragmented perspective view of the filter of  FIG. 23  shown received by the framework and a rod disposed in a slot formed in the framework maintaining the interaction between the rod and the filter; 
         FIG. 25  is an enlarged rear perspective view of the filter of  FIG. 23  shown received by the framework of the one of the filter assemblies and an electrical contact carried by the framework electrically contacting the electrode carried by the filter; 
         FIG. 26  is a fragmented top horizontal sectional view of one of the filter assemblies of the electrically stimulated air filter apparatus of  FIG. 7 ; 
         FIG. 27  is a fragmented side elevational view of the filter assembly of  FIG. 26  with portions thereof shown in vertical cross section for illustrative purposes; 
         FIG. 28  is a rear elevational view of one of the filter assemblies of the electrically stimulated air filter apparatus of  FIG. 7 ; 
         FIG. 29  is an enlarged fragmented perspective view of the filter assembly of  FIG. 28  illustrating opposed filters carried by the framework and electrical contacts carried by the framework contacting the electrodes of the opposed filters; 
         FIG. 30  is a front elevational view of the filter assembly of  FIG. 28 ; 
         FIG. 31  is a highly generalized rear elevational view of the electrically stimulated air filter apparatus of  FIG. 7 ; 
         FIG. 32  is an enlarged fragmented perspective view of opposed electrical contacts mounted to frameworks of the filter assemblies of the electrically stimulated air filter apparatus of  FIG. 6 ; 
         FIG. 33  is an enlarged fragmented perspective of the ionizer assemblies of the electrically stimulated air filter apparatus of  FIG. 6  illustrating opposed engaged electrical contacts mounted to frameworks of the ionizer assemblies; 
         FIG. 34  is an enlarged fragmented horizontal sectional view of the ionizer assemblies of the electrically stimulated air filter apparatus of  FIG. 6  illustrating the opposed engaged electrical contacts illustrated in  FIG. 33 ; 
         FIG. 35  is a fragmented perspective view of the electrically stimulated air filter apparatus of  FIG. 6  illustrating opposed filter and ionizer assemblies received by one of the supports; 
         FIG. 36  is a view very similar to that of  FIG. 3  illustrating the supports of the electrically stimulated air filter apparatus of  FIG. 6  attached to the housing upstream of the air conditioning apparatus; and 
         FIG. 37  is a view very similar to that of  FIG. 36  illustrating ionizer assemblies of the electrically stimulated air filter apparatus of  FIG. 6  shown mounted between the supports. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Turning now to the drawings, in which like reference characters indicate corresponding elements throughout the several views, attention is first directed to  FIG. 1  in which there is seen a prior art air conditioning system  100  mounted adjacent to a building  101  for providing the interior of building  101  with conditioning air. Air conditioning system  100  illustrated in  FIG. 1  is a conventional large-scale air conditioning system on the order of approximately 20-tons, and includes a housing  102  bounding an air flow pathway extending therethrough and which is coupled to receive intake air from inlet  103  and coupled to expel outtake air through outlet  104 . An air conditioning apparatus is disposed in the air flow pathway defined by housing  102  between inlet  103  and outlet  104  conditioning, i.e., temperature control, namely, heating or cooling, an air stream passing through the air flow pathway from inlet  103  to outlet  104 . Inlet  103  is coupled to receive intake air from building  101  and direct the intake air into the air flow pathway through housing  102 , and outlet  104  is coupled to receive conditioned air from the air flow pathway through housing  102  and expel the conditioned air into the interior of building  101 . As a matter of an example of a typical installation, air conditioning system  100  is mounted atop a supporting concrete pad  105  formed exteriorly of building  101 . 
     According to the principle of the invention,  FIG. 2  is a perspective view of the air conditioning system  100  of  FIG. 1  shown as it would appear configured with an electrically stimulated air filter apparatus constructed and arranged in accordance with the principle of the invention, which, in  FIG. 2 , is enclosed by a specialized cover  110  attached to housing  102 , and which actually forms part of housing  102  defining the air flow pathway through housing  102 . In  FIG. 2 , air conditioning system  100  is the existing system shown in  FIG. 1  illustrated as it would appear after retrofitting with the electrically stimulated air filter apparatus forming an enhanced air conditioning system for producing clean, conditioned air. The electrically stimulated air filter apparatus is disposed in the air flow pathway formed through housing  102  between inlet  103  and the conditioning air apparatus disposed in housing  102 , and is operative for entrapping contaminants in the air stream passing through the air flow pathway formed in housing  102 . The electrically stimulated air filter apparatus entraps and removes contaminants from the air stream upstream of the air conditioning apparatus between the air conditioning apparatus and inlet  103 . Consistent with the teachings set forth in this specification, an air conditioning system incorporating the electrically stimulated air filter apparatus constructed and arranged in accordance with the principle of the invention may be provided as an original installation. 
     As a matter of illustration and reference,  FIG. 3  is an enlarged fragmented perspective view of the prior art air conditioning system of  FIG. 1  with a portion of housing  102  illustrating air conditioning apparatus  108  disposed in air flow pathway  109  extending through housing  102 .  FIG. 4  is a view very similar to the view of  FIG. 3  illustrating an electrically stimulated air filter apparatus  120 , constructed and arranged in accordance with the principle of the invention, installed in air flow pathway  109  upstream of air conditioning apparatus  108  between inlet  103  and air conditioning apparatus  108 . Air conditioning apparatus  108  is not illustrated in  FIG. 4  because it is concealed from view by filter apparatus  120 . Filter apparatus  120  is a modular system. In operation, filter apparatus  120  entraps and removes contaminants from the air stream A passing through air flow pathway  109  to air conditioning apparatus  108  from inlet  103 , and does so between air conditioning apparatus  108  and inlet  103 . Filter apparatus  120  shown in  FIG. 4  is operatively coupled to a control system  121  illustrated in  FIG. 2 , which is provided, configured, and designed to control the operation of filter apparatus  120 , further details of which will be discussed later in this specification. As a matter of illustration,  FIG. 5  is an enlarged perspective view of control system  121  shown with a cover of a housing  122  thereof removed showing the components of control system  121 . 
     Filter apparatus  120  is modular. Referencing  FIG. 6  there is seen an exploded perspective view of filter apparatus  120 , constructed and arranged in accordance with the principle of the invention, including ionizer assemblies  130  and  131 , filter assemblies  132  and  133 , and supports  134  and  135  for securing ionizer assemblies  130  and  131  and filter assemblies  132  and  133  for installation in air flow pathway  109  upstream of air conditioning apparatus  108  as illustrated in  FIG. 4 . Ionizer assemblies  130  and  131  and filter assemblies  132  and  133  cooperate to form filter apparatus  120 . Supports  134  and  135  are utilized to mount ionizer assemblies  130  and  131  and filter assemblies  132  and  133  in place relative to each other and to air flow pathway  109 , in accordance with the principle of the invention. 
       FIGS. 7 and 8  illustrate filter apparatus  120  apparatus assembled, and a discussion of filter apparatus  120  assembled and operational will be discussed in detail, which will be followed by a detailed discussion of the various components of filter apparatus  120 .  FIG. 7  is a side elevational view of filter apparatus  120  shown assembled with portions thereof shown in vertical cross section for illustrative purposes, and  FIG. 8  is a top plan view of filter apparatus  120 , with portions thereof shown in horizontal cross section for illustrative purposes. An air stream denoted by the arrowed line A is denoted for orientation and reference in  FIGS. 7 and 8 . Air stream A through air flow pathway  109  is, of course, also denoted in  FIG. 4  for orientation and reference. 
     Referencing  FIGS. 7 and 8  in relevant part, ionizer assemblies  130  and  131  are mounted side-by-side relative to air stream A, and filter assemblies  132  and  133  are mounted side-by-side relative to air stream A opposing and downstream of ionizer assemblies  130  and  131 . Ionizer assembly  130  is operatively coupled to ionizer assembly  131 , and filter assembly  132  is operatively coupled to filter assembly  133 . Ionizer assemblies  130  and  131  are mounted in air stream A upstream of filter assemblies  132  and  133 . Ionizer assemblies  130  and  131  extend upright and together reside in a common vertical plane, and filter assemblies  132  and  133  are upright and together reside in a common vertical plane opposing and parallel to the common vertical plane in which ionizer assemblies  130  and  131  reside. The vertical planes defined by ionizer assemblies  130  and  131 , and filter assemblies  132  and  133  are substantially perpendicular relative to oncoming air stream A which flows first through ionizer assemblies  130  and  131  and then through filter assemblies  132  and  133 . As a matter of illustration and reference,  FIG. 9  is a fragmented front elevational view of filter apparatus illustrating ionizer assembly  131  received by and supported between supports  134  and  135 ,  FIG. 10  is a side elevational of filter apparatus  120  illustrating ionizer assembly  130  and filter assembly  132  received by and supported between supports  134  and  135 , and  FIG. 11  is a fragmented rear elevational view of filter apparatus  120  illustrating filter assembly  132  received by and supported between supports  134  and  135 . 
     Filter assemblies  132  and  133  support filters  140  each for entrapping contaminants in the air stream A. Filters  140  are supported in a common vertical plane, are each substantially equally sized and identical in structure, and cooperate forming an upstream face of filters  140  denoted generally at  141  facing ionizer assemblies  130  and  131 , and an opposed parallel downstream face of filters  140  denoted generally at  142  facing away from ionizer assemblies  130  and  131 . Filters  140  each carry a downstream electrode  143 . Downstream electrodes  143  are disposed along downstream face  142  of filters  140  in air stream A, and together reside in a common vertical plane denoted in  FIG. 7  at P 1 . Downstream electrodes  143  are each affixed to and contact one of filters  140 , further details of which will be described in detail later in this specification. Downstream electrodes  143  of filters  140  of filter assembly  132  are electrically connected, downstream electrodes  143  of filters  140  of filter assembly  133  are electrically connected, and downstream electrodes  143  of filters  140  of filter assembly  132  are electrically connected to downstream electrodes  143  of filters  140  of filter assembly  133 , according to the principle of the invention. 
     Ionizer assemblies  130  and  131  each supportionizer electrodes  150 , and an upstream electrode  151 . Ionizer electrodes  150  are supported in a common vertical plane denoted at P 2  in  FIG. 2  in air stream A upstream of, and parallel to, upstream face  141  of filters  140  and plane P 1  defined by downstream electrodes  143 . Ionizer electrodes  150  are substantially equally sized and identical in structure, the details of which will be discussed later in this specification. Ionizer electrodes  150  of ionizer assembly  130  are electrically connected, ionizer electrodes  150  of ionizer assembly  131  are electrically connected, and ionizer electrodes  150  of ionizer assembly  130  are electrically connected to ionizer electrodes  150  of ionizer assembly  131 . 
     Upstream electrodes  151  are supported in a common vertical plane denoted at P 3  in  FIG. 7  in air stream A upstream of, and parallel to, ionizer electrodes  150 . Plane P 3  defined by upstream electrodes  151  is upstream of and parallel to plane P 2  defined by ionizer electrodes  150 , and is upstream of, and parallel to, plate P 2  defined by downstream electrodes  143 . Upstream electrodes  151  are substantially equally sized and identical in structure. Upstream electrode  151  of ionizer assembly  130  is electrically connected to upstream electrode  151  of ionizer assembly  131 . 
     Ionizer electrodes  150  and  151  are electrically connected for carrying a potential. Upstream electrodes  151  are induced electrodes disposed in air stream A upstream of ionizer electrodes  150 , and downstream electrodes  143  are induced electrodes disposed in air stream A downstream of ionizer electrodes  150 . As previously mentioned in conjunction with  FIG. 7 , the vertical plane P 3  defined by upstream electrodes  151  is parallel to the vertical plane P 2  defined by ionizer electrodes  150  and the vertical plane P 1  defined by downstream electrodes  143 , whereby a gap or distance D 1  separates plane P 3  defined by upstream electrodes  151  and plane P 2  defined by ionizer electrodes  150 , and a gap or distance D 2  separates plane P 2  defined by ionizer electrodes  151  and plane P 1  defined by downstream electrodes  143 . 
     The potential carried by ionizer electrodes  150  of ionizer assemblies  130  and  131 , which is supplied by a high voltage power supply, imparts through induction a potential to upstream electrodes  151  of ionizer assemblies  130  and  131  forming ionizing field  160  between upstream electrodes  151  and ionizer electrodes  150  in juxtaposition along upstream electrodes  151 , and a potential to downstream electrodes  143  forming ionizing field  161  between downstream electrodes  143  and ionizer electrodes  150  in juxtaposition along downstream electrodes  143 . The engagement of each downstream electrode  143  against a corresponding filter  140  imparts ionizing field  161  to filters  140  and maintains ionizing field  161  with filters  140 , according to the principle of the invention. 
     The potential applied to ionizing electrodes  150  is substantially uniformly dispersed across ionizer electrodes  150  of ionizer assemblies  130  and  131  because ionizer electrodes  150  of ionizer assembly  130  are electrically connected, ionizer electrodes  150  of ionizer assembly  131  are electrically connected, and ionizer electrodes  150  of ionizer assemblies  130  and  131  are electrically connected, in accordance with the principle of the invention. Moreover, the induced potential formed in upstream electrodes  151  is also substantially uniformly dispersed across upstream electrodes  151  because upstream electrodes  151  of ionizer assemblies  130  and  131  are electrically connected, in accordance with the principle of the invention. Because the potential applied to ionizer electrodes  150  is substantially uniformly dispersed across ionizer electrodes  150  and because the induced potential across upstream electrodes  151  is also substantially uniformly dispersed across upstream electrodes  151 , ionizing field  160  formed along upstream electrodes  151  between upstream electrodes  151  and ionizer electrodes  150  is, thereby, substantially uniform, in accordance with the principle of the invention. 
     The induced potential formed in downstream electrodes  143  is substantially uniformly dispersed across downstream electrodes  143  of filters  140  of filter assemblies  132  and  133  because downstream electrodes  143  of filter assembly  132  are electrically connected, downstream electrodes  143  of filter assembly  133  are electrically connected, and downstream electrodes  143  of filter assembly  132  are electrically connected to downstream electrodes  143  of filter assembly  133 , in accordance with the principle of the invention. Because the potential applied to ionizer electrodes  150  is substantially uniformly dispersed across ionizer electrodes  150 , as discussed above, and because the induced potential across downstream electrodes  143  is also substantially uniformly dispersed across downstream electrodes  143 , ionizing field  161  formed along downstream electrodes  143  between downstream electrodes  143  and ionizer electrodes  150  is, thereby, substantially uniform, in accordance with the principle of the invention. 
     The potential across ionizer electrodes  150  is positive, and the potentials across upstream electrodes  151  and downstream electrodes  143  are each also positive but lesser in magnitude in comparison to the potential across ionizer electrodes  150 . Because the positive potentials across upstream electrodes  151  and downstream electrodes  143  are each lesser in magnitude than the positive potential applied across ionizer electrodes  150 , upstream electrodes  151  and downstream electrodes  143  are net negatively charged as compared to the potential across ionizer electrodes  150 . 
     Through induction, positively charged electrons flow or otherwise migrate from ionizer electrodes  150  across distance D 1  to upstream electrodes  151  and to downstream electrodes  143 , thereby forming the induced potential in upstream electrodes  151  and the induced potential in downstream electrodes  143 , according to the principle of the invention. As the positively charged electrons generated by ionizer electrodes  150  reach upstream electrodes  151  and induce the potential in upstream electrodes  151 , ionizing field  160  is formed along upstream electrodes  151  between upstream electrodes  151  and ionizer electrodes  150 . Ionizing field  160  is positive, but is lesser in magnitude in comparison to the potential across ionizer electrodes  150  and therefore has a net negative charge as compared to the potential across ionizer electrodes  150 . As the positively charged electrons generated by ionizer electrodes  150  reach downstream electrodes  143  and induce the potential in downstream electrodes  143 , ionizing field  161  is formed along downstream electrodes  143  between downstream electrodes  143  and ionizer electrodes  150 . Ionizing field  161  is positive, but is lesser in magnitude in comparison to the potential across ionizer electrodes  150  and therefore has a net negative charge as compared to the potential across ionizer electrodes  150 . According to the principle of the invention as previously indicated, the contact or engagement of each downstream electrode  143  against a corresponding filter  140  imparts and maintains ionizing field  161  in filters  140 , thereby imparting or otherwise inducing a positive charge to filters  54 , which is lesser in magnitude than the positive charge across ionizer electrode  55 . 
     Air stream A passes through filter apparatus  120  in a direction from upstream electrodes  151  of ionizer assemblies  130  and  131  to downstream electrodes  143  of filter assemblies  132  and  133 . As air stream A passes through filter apparatus  120 , air stream A passes first through upstream electrodes  151  and then through ionizing field  160 . As particles conveyed by air stream A, such as dust particles, mold particles, microbial particles, smoke particles, and other air-borne particles, encounter ionizing field  160 , ionizing field  160  imparts or otherwise induces a potential or electric charge to the particles suspended in air stream A causing the particles to become attracted to each other forming clusters of the particles, which are then conveyed by air stream A downstream through ionizer electrodes  150  to filters  143 , which entraps the clusters of particles thereby removing the clusters of particles from air stream A. The clusters of particles formed by the interaction of the particles with ionizing field  160  are positively charged. The positive charge to the clusters is imparted to the clusters by ionizing field  160 , and is lesser in magnitude than the positive charge of ionizing field  161  applied across filters  140 . Accordingly, as the clusters of particles reach filters  140 , the net negative charge applied to the clusters as compared to the net positive charge applied across filters  140  by ionizing field  161  causes the clusters to be electrically attracted to filters  140  thereby producing an aggressive and comprehensive removal of the clusters of particles from air stream A by filters  140  and a highly efficient and effective filtration efficiency, according to the principle of the invention. 
     When particles pass through ionizing field  160 , not only do the particles become attracted to one another to form clusters, a churning motion caused by the Van Der Walls Effect is imparted to the particles, which helps the particles impact one another and group together to form clusters of particles. The potential imparted to filters  140  by ionizing field  161  attracts and adheres the clusters of particles to filters  140 , according to the principle of the invention. 
     The structural details of ionizer assemblies  130  and  131  and filter assemblies  132  and  133  forming filter apparatus  120  will now be discussed. Ionizer assemblies  130  and  131  will first be discussed, followed by a discussion of filter assemblies  132  and  133 , in which the balance of the specification provides a discussion of the installation and operation of filter apparatus  120 . 
     Ionizer assemblies  130  and  131  are substantially identical in size, structure, and function. Accordingly, only the structure of ionizer assembly  130  will be discussed in detail, with the understanding that the ensuing discussion of ionizer assembly  130  applies in every respect to ionizer assembly  131  with the exception of any noted differences. 
     Referring to  FIG. 12 , which is a rear elevational view of ionizer assembly  130 , ionizer assembly  130  consists of a framework  170  formed of plastic, polyethylene or other nonconductive material or combination of nonconductive materials. Framework  170  is the supporting structure for ionizer electrodes  150 , and upstream electrodes  151 . 
     Framework  170  consists of a generally rectangular parametric frame  171  formed by opposed, elongate, parallel upper and lower members  172  and  173  interconnected at their respective opposed ends by opposed, elongate, parallel side members  174  and  175 . An elongate vertical support  176  is parallel to and disposed at an intermediate location between side members  174  and  175  and is secured to and interconnects upper member  172  with lower member  173 , and an elongate, horizontal support  177  is parallel to and disposed at an intermediate location between upper and lower members  171  and  172  and is secured to and interconnects side member  174  with side member  175 . Vertical support  176  and horizontal support  177  intersect and are joined at their respective midpoints. Referencing  FIG. 6 , for reference purposes it is to be understood that framework  170  has an upstream side denoted at  170 A, and an opposed downstream side denoted at  170 B. Parametric frame  171  is open from upstream side  170 A to downstream side  170 B as illustrated. 
     In the present embodiment, ionizer assembly  130  is fashioned with two ionizer electrodes  150  applied to downstream side  170 B of framework  170 , including upper and lower ionizer electrodes, extending between side members  174  and  175 . Ionizer electrodes  150  are each substantially identical in structure and function. Accordingly, the structural details of only the uppermost ionizer electrode, which is denoted at  150 ′ for clarity, will be discussed in detail, with the understanding that the ensuing discussion of upper electrode  150 ′ applies equally to each ionizer electrode of filter apparatus  120 . When operational ionizer electrodes  150  together function as, and may together be referred to as, the ionizer electrode of ionizer assembly  130 . 
     Upper electrode  150 ′ consists of a high voltage ionizing wire  180  having opposed ends  181  and  182  and a length extending between opposed ends  181  and  182 . End  181  is secured to framework  170  at side member  174  of framework  170 , and end  182  is secured to framework  170  at side member  175  of framework  170 . The length of ionizing wire  180  between ends  181  and  182  is strung across framework  170  from side member  174  to side member  175  forming a planar, upright array of spaced-apart, parallel courses or lengths of wires of the length of ionizing wire  180 . The spaced-apart, parallel courses or lengths of ionizing wire  180  extend across framework  170  from side member  174  to side member  175 , and extend across framework  170  between horizontal support  177  and upper member  172 . Ionizing wire  180  is formed by a single tungsten wire or other conductive material, which is attached to framework  170  and strung across framework  170  between upper member  172  and horizontal support  177  with non-conductive pins  184  affixed to upper and horizontal supports  172  and  177 . 
     Tension is applied to ionizing wire  180  maintaining tension across each of the courses of the length of ionizing wire  180  between ends  181  and  182  of ionizing wire, in accordance with the principle of the invention. Referring to  FIG. 13 , a tension spring  185  is coupled between end  182  of ionizing wire  180  and side member  175  of framework  170  applying the tension to ionizing wire  180 . In the present embodiment, tension spring  185  is fashioned of spring steel, a nickel-based spring alloy, or other material or combination of materials having a substantially constant moduli of elasticity as is typical with tension springs, and includes a wire formed into coils  186 , in which the two opposing outermost coils  186 A and  186 B lead to tag ends  187  and  188 , respectively. Tag end  187  is secured to end  182  of ionizing wire  180 , and tag end  188  is secured to side member  175  of framework  170 . In the present embodiment, tag end  187  is formed with a hook  190 , which is received by a corresponding loop  191  formed in end  182  of wire  180  thereby securing tension spring  185  to end  182  of ionizing wire  180 , although this arrangement of engagement elements can be reversed if so desired. Tag end  188  is formed with a loop  192  that accepts a fastener  193 , in this instance a threaded fastener, that is, in turn, secured to side member  175  of framework  170 . Those having regard for the art will readily appreciate that any suitable engagement structure may be utilized for securing tag end  187  to end  182  of ionizing wire  180 , and for securing tag end  188  to framework  170  without departing from the invention. End  181  of ionizing wire  180  is similarly attached to framework  170  with a tension spring  185 , whereby tension springs  185  together supply the applied bias to ionizing wire  180  in accordance with the principle of the invention. Although tension springs  185  applied to ends  181  and  182 , respectively, of ionizing wire  180  supply the applied tension to ionizing wire  180 , only one tension spring may be utilized in conjunction with one of the ends of ionizing wire  180  for supplying the applied tension to ionizing wire  180 . 
     Referencing  FIG. 14 , an electrical contact or plug  200 , such as a banana plug or the like, is formed in side member  174 , which is electrically connected to a pair of opposed parallel supply wires  201  and  202  with a conductive strip  203  of metal. Supply wires  201  and  202  are each formed of a single tungsten wire and are preferably soldered to strip  203  providing an electrical connection therebetween. Looking to  FIG. 12 , supply wires  201  and  202  extend along horizontal support  177  from side member  174  to side member  175 , and are each electrically connected, such as by soldering, to a contact  204  attached to framework  170  at side member  175 . Supply wire  201  is in electrical contact with ionizer electrode  150 ′, supply wire  202  is in contact with ionizer electrode  150 , and supply wires  201  and  202  are each in electrical contact with electrical contact  204  thereby forming an electrical connection of ionizer electrodes  150 ′ to ionizer electrode  150 . Supply wires  201  and  202  each electrically contact the courses of ionizing wire  180  of the respective ionizer electrodes  150 ′ and  150 , whereby a potential imparted to supply wires  201  and  202  is, in turn, imparted to ionizer electrodes  150 ′ and  150 . 
     With momentary reference to  FIG. 34 , illustrated is electrical contact  204  mounted to framework  170  at side member  175 . Electrical contact  204  consists of an elongate member or spline formed of spring steel or other springy conductive metal having a proximal end  204 A, an opposed distal end  204 B, and an intermediate portion  204 C between proximal and distal ends  204 A and  204 B. Intermediate portion  204 C extends through, and is secured relative to, a sleeve  194  formed in framework  210  through side member  175 . Proximal end  204 A is integral with an enlarged head  195  located against the inner side of side member  175 , and distal end  204 B is integral with an electrical contact  196  extending outwardly from side member  175 . Supply wires  201  and  201  are electrically connected to enlarged head  195  of proximal end  204 A, such as by soldering or the like. The fit between intermediate portion  204 C and sleeve  194  is relatively close and tight thereby providing a secure engagement of electrical contact  204  relative to side member  175  of framework  170  of ionizer assembly  130 . If desired, the engagement between intermediate portion  204 C and sleeve  195  may be enhanced with an adhesive, one or more rivets, screws, etc. 
     Referring back to  FIG. 6 , upstream electrode  151  is constructed of porous conductive material, typically a flattened and expanded aluminum grid, screen or mesh. Upstream electrode  151  is applied against upstream side  170 A of parametric frame  171 , whereby the parametric edge of upstream electrode  151  is secured to the upstream edges of upper and lower members  172  and  173  and side members  174  and  175  with a non-conductive adhesive, although non-conductive threaded fasteners or rivets or the like may be used, if desired. Because framework  170  is formed of non-conductive material, upstream electrode  151  is, in a particular embodiment, electrically isolated being under no influence or control by any device attached thereto, such as a ground or resistor or other device capable of influencing the induced potential thereacross provided by ionizer electrodes  150 . Because upstream electrode  151  is electrically isolated in a preferred embodiment, upstream electrode  151  is a “floating” electrode being free of the influence of a ground or resistor or other device, the potential imparted to upstream electrode  151  through induction by ionizer electrodes  150  of ionizer assembly  130  is lower in magnitude than the potential applied across ionizer electrodes  151  as previously discussed, and the incidence of arcing occurring between ionizer electrodes  150  and upstream electrode  151  is restrained. If desired, upstream electrode  151  may be grounded. However, grounding upstream electrode  151  tends to increase the incidence of arcing between ionizer electrodes  150  and upstream electrode  151 , whereby distance D 1 , referenced in  FIG. 7 , between ionizer electrodes  150  and upstream electrode  151  must be carefully chosen to prevent the incident of arcing therebetween. 
     In the preferred embodiment set forth herein, upstream electrode  151  is formed of a single sheet of flattened and expanded aluminum grid, screen or mesh. If desired, upstream electrode  151  may be formed of a plurality of sheets of flattened and expanded aluminum grids, screens or meshes. 
     Referring back to  FIG. 12 , applied to framework  170  at side member  175  are opposed electrical contacts  205 . Electrical contacts  205  extend outwardly relative to side member  175 . One electrical contact  205  is located adjacent to upper member  172 , and the other electrical contact  205  is located adjacent to lower member  173 . Electrical contacts  205  are identical in every respect, and the details of only one of electrical contacts will be discussed in conjunction with  FIG. 33 , with the understanding that the ensuing discussion applies to each electrical contact  205 . 
     Referencing  FIGS. 33 and 34 , an electrical contact  205  is shown, and is applied and secured to side member  175  at upstream side  170 A of framework  170 . Electrical contact  205  consists of an elongate member or spline formed of spring steel or other springy conductive metal having a proximal end  205 A, an opposed distal end  205 B, and an intermediate portion  205 C between proximal and distal ends  205 A and  205 B. Intermediate portion  205 C is secured to the upstream edge of side member  175  with a threaded fastener  206 , although a rivet, adhesive or other selected fastener or combination of fastener may be used to secure electrical contact  205  in place. Proximal end  205 A is integral with an electrical contact  207  extending outwardly relative to side member  175  of framework  170 . Distal end  205 B extends inwardly relative to side member  175  and is received in contact against upstream electrode  151 , according to the principle of the invention. In the present embodiment, two electrical contacts  205 , and corresponding electrical contacts  207  integral therewith, are incorporated with ionizer assembly  130 , although less or more may be utilized if desired. 
     The structural details of ionizer assembly  130  have been described. As previously mentioned, ionizer assemblies  130  and  131  are substantially identical, and the discussion above relating to ionizer assembly  130  applies to ionizer assembly  131 . One difference between ionizer assembly  130  and ionizer assembly  131  is that electrical contacts  205 , and the corresponding electrical contacts  207  integral therewith, of ionizer assembly  131  are attached to framework  170  at side member  174 , in which case electrical contacts  207  project outwardly relative to side member  174  of ionizer assembly  131 .  FIGS. 33 and 34  illustrate this aspect showing side member  174  of framework  170  of ionizer assembly  131 , an electrical contact  205  mounted to framework  170  at side member  174  of ionizer assembly  131 , and electrical contact  207  integral with electrical contact  205  projecting outwardly relative to side member  174  of ionizer assembly  131 . 
     As previously mentioned, when filter apparatus  120  is assembled upstream electrode  151  of ionizer assembly  130  is electrically connected to upstream electrode  151  of ionizer assembly  131 , in which electrical contacts  205  between ionizer assemblies  130  and  131  provide this electrical connection between ionizer assemblies  130  and  131 . In particular, when filter apparatus  120  is assembled ionizer assemblies  130  and  131  are mounted side-by-side and extend upright and together reside in a common vertical plane, in which side member  175  of ionizer assembly  130  faces and confronts side member  174  of ionizer assembly  131  as illustrated in  FIGS. 33 and 34 . Electrical contacts  205 , and electrical contacts  207  integral therewith, between ionizer assembly  130  and ionizer assembly  131  relate, whereby electrical contacts  207  of ionizer assembly  130  contact electrical contacts  207  of ionizer assembly  131  thereby electrically connecting upstream electrode  151  of ionizer assembly  130  to upstream electrode  151  of ionizer assembly  131 , in accordance with the principle of the invention. 
     Another difference between ionizer assembly  130  and ionizer assembly  131  is that electrical contact  204  of ionizer assembly  131  is attached to framework  170  at side member  174  of ionizer assembly  131 , in which case electrical contact  196  projects outwardly relative to side member  174  of ionizer assembly  131 .  FIG. 34  illustrates this point showing side member  174  of framework  170  of ionizer assembly  131 , electrical contact  204  mounted to framework  170  at side member  174  of framework  170  of ionizer assembly  131  and electrical contact  196  integral with proximal end  204 A projecting outwardly relative to side member  174  of ionizer assembly  131 . 
     As previously mentioned, when filter apparatus  120  is assembled ionizer electrodes  150  of ionizer assembly  130  are electrically connected to ionizer electrodes  150  of ionizer assembly  131 . Electrical contacts  204  between ionizer assemblies  130  and  131  provide this electrical connection between ionizer assemblies  130  and  131 . In particular, when filter apparatus  120  is assembled ionizer assemblies  130  and  131  are mounted side-by-side and extend upright and together reside in a common vertical plane, in which side member  175  of ionizer assembly  130  faces and confronts side member  174  of ionizer assembly  131  as illustrated in  FIG. 34 . Electrical contacts  204  between ionizer assembly  130  and ionizer assembly  131  relate, whereby electrical contact  196  of ionizer assembly  130  contacts electrical contact  196  of ionizer assembly  131  thereby electrically connecting supply wires  201  and  202  of ionizer assembly  130  to supply wires  201  and  202  of ionizer assembly  131  thereby, in turn, electrically connecting ionizer electrodes  150  of ionizer assembly  130  to ionizer electrodes  150  of ionizer assembly  131 , in accordance with the principle of the invention. 
     Having described the structural details of ionizer assembly  130 , in which the discussion thereof applies equally to ionizer assembly  131  with the exception of the noted differences described above, the structural details of filter assemblies  132  and  133  will now be discussed. Filter assemblies  132  and  133  are substantially identical, both in size and in structure. Accordingly, only the structure of filter assembly  132  will be discussed in detail, with the understanding that the ensuing discussion of filter assembly  132  applies to filter assembly  133  in every respect with the exception of any noted differences. 
     Referring to  FIG. 6 , filter assembly  132  consists of a framework  210  formed of plastic, polyethylene or other nonconductive material or combination of nonconductive materials. Framework  210  receives filters  140 , and is the supporting structure for filters  140 . Framework  210  consists of a generally rectangular parametric frame  211  formed by opposed, elongate, parallel upper and lower members  212  and  213  interconnected at their opposed ends by opposed, elongate, parallel side members  214  and  215 . An elongate vertical support  216  is parallel to and disposed at an intermediate location between side members  214  and  215  and is secured to and interconnects upper member  212  with lower member  213 . An elongate, horizontal support  217  is parallel to and disposed at an intermediate location between upper and lower members  211  and  212  and is secured to and interconnects side member  214  with side member  215 . Vertical support  216  and horizontal support  217  intersect and are joined at their respective midpoints, and cooperate with parametric frame  211  to form receiving areas or compartments  218  for filters  140 . In the present embodiment, framework  210  incorporates four compartments  218 , including two upper compartments  218  disposed side-by-side on either side of vertical support  216 , and two lower compartments  218  disposed side-by-side on either side of vertical support  216 . Compartments  218  are substantially equal in size and shape. For reference purposes it is to be understood that framework  210  has an upstream side denoted at  210 A, and an opposed downstream side denoted at  210 B, and that parametric frame  211  is open from upstream side  210 A to downstream side  210 B as illustrated. 
     Compartments  218  each receive and hold a filter  140 , in accordance with the principle of the invention. The size and shape of each filter  140  relates to the size and shape of each corresponding compartment  218 . In the present embodiment, the size and shape of each filter  140  and each corresponding compartment  218  is generally rectangular, although other corresponding shapes can be implemented if so desired. The size of each compartment  218  is only somewhat greater than the size of the corresponding filter  140  ensuring a relatively close fit, yet not so close making it easy to install and remove filters  140  relative to compartments  218 . 
     Filters  140  are substantially identical, both in size and in structure, as are each of compartments  218 . Accordingly, only the structure of one filter  140  will be discussed in detail, with the understanding that the ensuing discussion of one filter  140  applies in every respect to each one of filters  140 . For ease of discussion, the filter to be discussed in detail is denoted at  140 ′. 
     Referencing  FIG. 15 , filter  140 ′ is illustrated, which is representative of each of filters  140  and which consists of a broad pleated body  220  formed by opposed, parallel upper and lower ends  221  and  222 , opposed parallel sides  223  and  224 , and pleats  225 . Equally spaced-apart pleats  225  extend vertically from upper end  221  to lower end  222 , and are parallel relative to sides  223  and  224  and extend between sides  223  and  224 . As seen in  FIG. 22 , which is a sectional view taken along line  22 - 22  of  FIG. 15 , and  FIG. 26 , which is a fragmented top horizontal sectional view of filter assembly  132  illustrating filter  140 ′ shown installed relative to framework  210 , pleats  235  are clearly illustrated, and define and are separated by equally spaced-apart spaces  236  formed by and between pleats  235 . Pleats  235  can, if desired, be constructed to extend horizontally from side  223  to side  224 . In shape, pleats  235  and spaces  236  formed by and between pleats  235  are each an elongate, triangular shape. 
     The broad, pleated characteristics of filter  140 ′ provides an increased surface area allowing for capture of a greater quantity of contaminants, including clusters of particles. Filter  140 ′ is formed of dielectric material, such as glass or other plastic fiber material having a low dielectric and low conductivity. According to the preferred embodiment set forth herein, filter  140 ′ is preferably fashioned of fiberglass with approximately 6-10% binder material incorporated to bond the fiberglass together in the formation of filter  140 ′. Filter  140 ′ neither contains nor incorporates conductive material. As a matter of illustration and reference,  FIG. 16  is a front elevational view of filter  140 ′,  FIG. 17  is a side elevational view of filter  140 ′,  FIG. 18  is a rear elevational view of the filter  140 ′, and  FIG. 19  is a side elevational view of the filter  140 ′ with portions thereof shown in vertical cross section for illustrative purposes. In the present embodiment, filter  54  is approximately 18-22 inches in width, approximately 24-30 inches in height, approximately 4-6 inches deep, and is formed of dielectric material that is approximately 0.22 inches thick. 
     Referencing  FIG. 15 , filter  140 ′ has a front or upstream face  140 A, and an opposed parallel rear or downstream face  140 B. Downstream electrode  143  is constructed of porous conductive material, typically a flattened and expanded aluminum grid, screen or mesh defining an array of equally-sized openings  144 . Downstream electrode  143  is applied against downstream face  140 B of filter  140 , and relates to the size of downstream face  140 B thereby completely covering downstream face  140 B. In other words, downstream electrode  143  is coextensive relative to downstream face  140 B. Preferably, the parametric edge of downstream electrode  143  is adhered to the perimeter edge of filter  140  formed by the downstream edges of upper and lower ends  221  and  222  and sides  223  and  224  at downstream face  140 B of filter  140 ′ with a non-conductive adhesive. Downstream electrode  143  is in full contact with downstream face  140 B of filter  140 ′. 
     In the preferred embodiment set forth herein, downstream electrode  143  is formed of a single sheet of flattened and expanded aluminum grid, screen or mesh. If desired, downstream electrode  143  may be formed of a plurality of sheets of flattened and expanded aluminum grids, screens or meshes. 
     Referencing  FIG. 15 , filter  140  incorporates a plurality of spacer elements  240 . Spacer elements  240  are applied to filter  140 ′ in a direction toward downstream electrode  143 , and extend into pleated body  220  through openings  144  formed by downstream electrode  143 , in accordance with the principle of the invention. In the preferred embodiment disclosed herein, spacer elements  240  are parallel relative to each other and relative to upper and lower ends  221  and  222  of pleated body  220 , extend along substantially the entire width of pleated body  220  from side  223  to side  224 , and are disposed at substantially equal spaced intervals between upper and lower ends  221  and  222 . Spacer elements  240  function to maintain the shape of pleated body  220 , namely, the shape pleats  235  from upper end  221  of pleated body  220  to lower end  222  of pleated body  220  preventing pleats  235  from collapsing and moving relate to each other in response to an air stream passing through pleated body  220  in a direction from upstream face  140 A to downstream face  140 B which could otherwise alter the shape of pleats  235  and the shape and size of spaces  236  formed by and between pleats  235  and, thus, the filtering efficiency of filter  140 ′. As illustrated in  FIGS. 15 and 18 , filter  140 ′ incorporates six spacer elements  240  between upper end  221  of pleated body  220  and lower end  222  of pleated body  220 , although less or more may be utilized as so desired or as so needed. 
     Spacer elements  240  are substantially identical in size, structure, and function, and are each formed of non-conductive material, such as polyethylene, polypropylene, or other selected plastic or plastic-like material. One spacer element  240  is detached and removed from filter  140 ′ in  FIG. 15  for illustrative purposes, in which the illustrated spacer element  240  consists of a straight, elongate body  241  having opposed ends  242  and  243 , and a plurality of equally spaced-apart and equally-sized fingers  244  extending in a parallel row from elongate body  241  from end  242  to end  243 . Fingers  244  each have an elongate, triangular shape. Moreover, the size and shape of fingers  244  each generally relate to the cross sectional size and shape of each space  236  formed by and between pleats  235 . 
     Spacer elements  240  are each applied to filter  140 ′ and form part of filter  140 ′. Referencing  FIG. 22 , which is a sectional view taken along line  22 - 22  of  FIG. 15 , a spacer element  240  is illustrated applied to filter  140 ′. Applied to filter  140 ′ in accordance with the principle of the invention, fingers  244  are applied through openings  144  formed in downstream electrode  143  and elongate body  241  is applied exteriorly against downstream electrode  143 , whereby fingers  244  extend into and through openings  144  formed in downstream electrode  143  from elongate body  241  into alternating ones of spaces  236  as illustrated toward upstream face  140 A of filter body  220 . In other words, every other one of spaces  236  facing downstream electrode  143  is occupied by one finger  244 , whereby pleats  235  are thereby inhibited from collapsing and moving relative to each other in response to an air stream passing through pleated body  220  in a direction from upstream face  140 A to downstream face which could otherwise alter the shape of pleats  235  and the shape and size of spaces  236  formed by and between pleats  235 . As a matter of illustration and reference,  FIG. 19  is a side elevational view of filter  140 ′ with portions thereof shown in vertical cross section illustrating one finger  244  from adjacent spacer elements  240  received in space  236  formed along pleat  235 , in which fingers  244  are parallel relative to one another and also relative to upper and lower ends  221  and  222  of pleated body  220 , and extend into pleated body  220  from downstream electrode  143  at downstream face  140 A of pleated body  220  toward upstream face  140 A of pleated body  220 . In this regard, it is to be understood that the parallel rows of fingers  244  of the plurality of spacer elements  240  are parallel relative to each other and relative to upper and lower ends  221  and  222  of pleated body  220  in accordance with the principle of the invention. 
     To secure spacer elements  240  in place after applying them to filter  140 ′ as herein specifically described, a non-conductive adhesive is applied adhering the elongate body  241  of each spacer element  240  to downstream electrode  143  and downstream face  140 B of pleated body  220 . Preferably, the non-conductive adhesive is applied along the entire length of the elongate body  241  of each spacer element  240  from end  242  to end  243  in the form of one or more beads of the non-conductive adhesive. As a matter of illustration and reference,  FIG. 20  is a sectional view taken along line  20 - 20  illustrating beads  250  of non-conductive adhesive applied between the elongate body  241  of the illustrated spacer element  240 , the downstream electrode  143  and the downstream face  140 B of pleated body  220  of filter  140 ′. In  FIG. 20 , two beads  250  of the non-conductive adhesive are applied, one bead  250  formed on one side of the elongate body  241  and the second of the two beads  250  formed on the opposed side of the elongate body  241 .  FIG. 21  is an enlarged fragmented perspective view illustrating the spacer element  240  of  FIG. 20  applied to filter  140 ′ and one of the beads  250  of non-conductive adhesive applied to one side of the elongate body  241  and interacting between the elongate body  241 , the downstream electrode  143 , and the downstream face  140 B of pleated body  220  of filter  140 ′. The application of spacer elements  240  to filter  140 ′ not only inhibits or prevents pleats  235  from collapsing and moving relative to each other in response to an air stream passing through pleated body  220  in a direction from upstream face  140 A to downstream face  140 B which could otherwise alter the shape of pleats  235  and the shape and size of spaces  236  formed by and between pleats  235 , but also applies downstream electrode  143  into intimate contact against downstream face  140 B of pleated body  220 , in accordance with the principle of the invention. More particularly, the adhesion formed between the elongate bodies  241  of spacer elements  240  applies downstream electrode  143  against downstream face  140 B. 
     As with each filter  140 , filter  140 ′ is received by one of the compartments  218  formed in framework  210  as illustrated in  FIGS. 23 and 26 . In  FIGS. 23 and 26 , filter  140 ′ shown received in a compartment  218  of framework  210 , whereby downstream face  140 B ( FIG. 26 ) of filter  140 ′ and downstream electrode  143  ( FIG. 26 ) of filter  140 ′ face downstream side  210 B of framework  210  and upstream face  140 A of filter  140 ′ faces upstream side  210 A of framework  210 .  FIG. 23  clearly shows how the shape of filter  140 ′ relates to the shape of the compartment  218  receiving and maintaining filter  140 ′.  FIG. 25  is an enlarged rear perspective view of filter  140 ′ shown received in a compartment  218  of framework  210  viewed from downstream side  210 B of framework  210 , whereby downstream face  140 B of filter  140 ′ and downstream electrode  143  of filter  140 ′ face downstream side  210 B of framework  210  and upstream face  140 A of filter  140 ′ faces upstream side  210 A of framework  210 . 
       FIG. 28  is a rear elevational view of filter assembly  132  illustrating filters  140 , including filter  140 ′, received in compartments  218  formed by framework  210 , and  FIG. 30  is a front elevational view of filter assembly  132  illustrating filters  140 , including filter  140 ′, disposed in compartments  218  formed by framework  210 . As seen in  FIG. 28 , widened strips  255  of material are applied to the downstream edges of upper, lower, and side members  211 - 214  of parametric frame  210 , and to the downstream edges of vertical and horizontal supports  216  and  217 , which cooperate to form parametric rims each directed inwardly relative to a corresponding compartment  218 . The outer perimeter of each filter  140  is received against the corresponding parametric rim formed at the corresponding compartment  218  by widened strips  255 , which prevents filters  140  from simply falling outwardly through the downstream side  210 B of framework  210  from compartments  218 . 
     In  FIG. 25 , widened strips  255  are shown formed on the parametric rim formed by framework  210  relating to compartment  218  in which filter  140 ′ is received, and which is the case with each compartment  218  formed by framework  210 . As clearly seen in  FIG. 25 , the perimeter of filter  140 ′ along downstream face  140 B is received against the corresponding parametric frame formed by widened strips  255  of framework  210  relating to the compartment  218  receiving filter  140 ′ thereby preventing filter  140 ′ from falling outwardly from compartment  218  from downstream side  210 B of framework  210 . Applied inwardly to widened strips  255  between the parametric frame defined by widened strips  255  relating to the compartment  218  receiving filter  140 ′ are strips  256  of foam rubber, which provide a certain amount of compliance between filter  140 ′ and the parametric frame and which form a seal inhibiting air from flowing between the perimeter of filter  140 ′ and framework  210 . Each filter  140  relates to a corresponding parametric frame as described in connection with filter  140 ′, and strips  256  of foam rubber are preferably applied between the perimeter of each filter  140  and the corresponding parametric frame formed along downstream side  210 A of framework  210 . 
     Referencing  FIG. 28 , framework  210  supports electrical contacts, which are received against downstream electrodes  143  of filters  140 , including filter  140 ′, which electrically connect the downstream electrodes  143  of the two uppermost filters  140 , one of which is filter  140 ′, and which electrically connect the downstream electrodes  143  of the two lowermost filters  140 . The electrical contacts electrically connecting the downstream electrodes  143  of the two uppermost filters  140  include opposed end electrical contacts  260  and  261  and an intermediate electrical contact  262 . End electrical contact  260  is affixed framework  210  at side member  214  and is received against the downstream electrode  143  of filter  140 ′ received in the uppermost compartment  218  formed between side member  214  and vertical support  216  and upper member  212  and horizontal support  217 . End electrical contact  261  is affixed to framework  210  at side member  215  and is received against the downstream electrode  143  of filter  140  received in the uppermost compartment  218  formed between side member  215  and vertical support  216  and upper member  212  and horizontal support  217 . Intermediate electrical contact  262  is affixed to framework  210  at vertical support  216  and is concurrently received against the downstream electrode  143  of filter  140 ′ received in the uppermost compartment  218  formed between side member  214  and vertical support  216  and upper member  212  and horizontal support  217 , and filter  140  received in the uppermost compartment  218  formed between side member  215  and vertical support  216  and upper member  212  and horizontal support  217 . Electrical contacts  260 ,  261 , and  262  provide the electrical contact between the respective downstream electrodes  143  of the uppermost filters. 
     With filter  140 ′ properly positioned in the corresponding compartment  218 , downstream electrode  143  of filter  140 ′ is concurrently applied against electrical contact  260  as seen in  FIGS. 25 and 26 , and against electrical contact  262  as seen in  FIGS. 26 and 29 . As illustrated in  FIGS. 25 and 26 , electrical contact  260  consists of an elongate member or spline formed of spring steel or other springy conductive metal having a proximal end  270 , an opposed distal end  271 , and an intermediate portion  272  between proximal and distal ends  270  and  271 . Intermediate portion  272  extends through, and is secured relative to, a sleeve  273  formed in framework  210  between side member  214  and the widened strip  255  attached to side member  214 . Proximal end  270  is connected to a ground wire  275 , and distal end  271  is received or otherwise abutted against downstream electrode  143  of filter  140 ′, and ground wire  275  is, in turn, electrically connected to an electrical contact or ground plug  276  formed in side member  214  as shown in  FIG. 23 . 
     The fit between intermediate portion  272  and sleeve  273  is relatively close and tight thereby providing a secure engagement of electrical contact  260  relative to side member  214  of framework  210 . If desired, the engagement between intermediate portion  272  and sleeve  273  may be enhanced with an adhesive, one or more rivets, screws, etc. 
     Looking to  FIGS. 26 and 29 , electrical contact  262  consists of an elongate member or spline formed of spring steel or other springy conductive metal having opposed free or distal ends  280  and  281  on either side of an intermediate portion  283 . Intermediate portion  282  extends through, and is secured relative to, a sleeve  283  formed in framework  210  between vertical support  216  and the widened strip  255  attached to vertical support  216 . Distal end  280  of electrical contact  262  is received or otherwise abutted against downstream electrode  143  of filter  140 ′, and the opposed distal end  281  of electrical contact  262  is received or otherwise abutted against downstream electrode  143  of the adjacent uppermost filter  140  received in the adjacent compartment  218 . The fit between intermediate portion  282  and sleeve  283  is relatively close and tight thereby providing a secure engagement of electrical contact  262  relative to vertical support  216 . If desired, the engagement between intermediate portion  282  and sleeve  283  may be enhanced with an adhesive, one or more rivets, screws, etc. 
     Referring to  FIG. 32 , electrical contact  261  consists of an elongate member or spline formed of spring steel or other springy conductive metal having a proximal end  290 , an opposed distal end  291 , and an intermediate portion  292  between proximal and distal ends  290  and  291 . Intermediate portion  292  extends through, and is secured relative to, a sleeve  293  formed in framework  210  between side member  215  and the widened strip  255  attached to side member  215  of framework  210 . Proximal end  290  is integral with an electrical contact  294  extending outwardly relative to side member  215  of framework  210 , and distal end  291  received or otherwise abutted against downstream electrode  143  of the corresponding uppermost filter  140  received in the corresponding compartment  218  adjacent to the other uppermost filter  140 ′ denoted in  FIG. 26 . The fit between intermediate portion  292  and sleeve  293  is relatively close and tight thereby providing a secure engagement of electrical contact  261  relative to side member  215  of framework  210 . If desired, the engagement between intermediate portion  292  and sleeve  293  may be enhanced with an adhesive, one or more rivets, screws, etc. 
     Referring to  FIG. 28 , the lowermost filters  140  also relate to corresponding electrical contacts  260 ,  261 , and  262  mounted to framework  210 , and it is to be understood that the foregoing discussion of electrical contacts  260 ,  261 , and  262  relating to the uppermost filters  140 , including filter  140 ′, of filter assembly  132  apply equally to electrical contacts  260 ,  261 , and  262  in connection with the lowermost filters  140  of filter assembly  132 . In response to applying filters  140  to compartments  218  formed by framework  210  of filter assembly  132 , the electrical contacts  260 ,  261 , and  262  attached to framework  210  along downstream side  210 B electrically interconnect the downstream electrodes  143  of the plurality of filters  140 . Proximal end  270  of electrical contact  260  associated with lowermost filters  140  is connected to a ground wire  275 , which is, in turn, electrically connected to electrical contact or ground plug  276  formed in side member  214  as shown in  FIG. 23 . 
     After installing filters  140  into the corresponding compartments  218  formed in framework  210  as seen in  FIG. 30 , abutments  300  are then attached to framework  210  which act against filters  140  thereby urging downstream electrodes  143  of filters  140  against electrical contacts  260 ,  261 , and  262  mounted to framework  210  along downstream side  210 B, in accordance with the principle of the invention, and which also prevent filters  140  from falling outwardly from compartments  218  from upstream side  210 A of framework  210 . In the present embodiment, abutments  300  are formed of plastic, polyethylene or other nonconductive material or combination of nonconductive materials, and each consist of an elongate rod  301  mounted to framework  210  along downstream side  210 A. Rods  301  are each received in corresponding slots  302  formed in the upstream edges of side members  214  and  214  and vertical support  216 . 
     Rods  301  are elongate, have opposed ends  303  and  304  and a length  305  therebetween, run parallel relative to each other and to upper and lower members  212  and  213  of framework  210 , are disposed at spaced intervals between upper member  212  and lower member  213 , and extend across upstream side  210 A of framework  210  from side member  214  to side member  215 . Two rods  301  are applied to each filter  140 , one adjacent to the upper end  221  thereof and the other rod  301  adjacent to the lower end  222  thereof. Each rod  301  extends across upstream side  210 A of framework  210  and is applied against the upstream face  140 A of two adjacent filters  140 . 
     Slots  302  are each identical. Looking to  FIG. 24 , one of the slots  302  formed in the upstream edge of side member  214  is illustrated. As seen in  FIG. 24 , slot  302  has an inwardly-directed portion  310  that leads to a down-turned portion  311 . Rod  301  is initially received in portion  310 , and is then applied downwardly into down-turned portion  311  of slot  302 . Rods  301  are received in the down-turned portions of corresponding ones of slots  302 , which maintains rods  301  in forcible engagement against the upstream faces  140 A of the filters  140  received in compartments  218  formed by framework  210  thereby urging downstream electrodes  143  of filters  140  of filter assembly  132  against electrical contacts  260 ,  261 , and  262  as previously discussed. Rods  301  are removed simply by reversing the operation used to install them, at which point filters  140  may be removed as needed for repair, cleaning, or replacement. 
       FIG. 27  is a fragmented side elevational view of filter assembly  132  with a portion thereof shown in vertical cross section showing rods  301  as they would appear received and maintained in down-turned portions  311  of corresponding slots  302 , and forcibly applied against the upstream faces  140 A of adjacent filters  140  thereby urging filters  140  toward downstream side  210 B of framework  210  away from upstream side  210 A thereby urging the corresponding downstream electrodes  143  against the electrical contacts formed on downstream side  210 A of framework  210 . In  FIG. 27 , free ends  280  of electrical contacts  262  are illustrated, one free end  280  of one electrical contact  262  contacting the downstream electrode  143  of uppermost filter  140 ′, and the free end  280  of the opposed electrical contact  262  contacting the downstream electrodes  143  of the corresponding lowermost filter  140  underlying filter  140 ′.  FIG. 23  illustrates opposed rods  301  received in corresponding slots  302  formed in the upstream edges of side member  214  and vertical support  216 , in which the lengths  305  of rods  301  are illustrated applied against upstream face  140 A of filter  140 ′.  FIG. 26  is an exemplary drawing illustrating a rod  301  received and maintained in slots  302  interacting against upstream faces  140 A of adjacent filters  140 ′ and  140  urging downstream electrodes  143  of filters  140 ′ and  140  against electrodes  260  and  262 . 
     Referencing  FIG. 30 , each rod  301  defines a longitudinal axis A extending from end  303  to end  304 . Structure is provided that interacts between each rod  301  and framework  210  preventing movement of each rod  301  relative to framework  210  along longitudinal axis A of each rod  301 . In the present embodiment, rods  301  support stops  306 . The stops  306  of each rod  301  interact with framework  210  preventing the rod  301  from moving relative to framework  210  along longitudinal axis A. In the present embodiment, stops  306  are enlargements carried by ends  303  and  304  of each rod  301 . Stop  303  is located outboard of side member  214 , and stop  215  is located outboard of side member  215 , and together stops  306  interact with side members  214  and  215 , respectively, preventing movement of the rod  301  along longitudinal axis A. If desired, one or more stops may be applied at an intermediate location so as to interact with vertical support  216 . 
     The structural details of filter assembly  132  have been described. As previously mentioned, filter assemblies  132  and  133  are substantially identical, and the discussion above relating to filter assembly  131  applies to filter assembly  133 . One difference between filter assembly  132  and filter assembly  133  is that electrical contacts  261 , and the corresponding electrical contacts  294  integral therewith, of filter assembly  133  are attached to framework  210  at side member  214 , in which case electrical contacts  294  project outwardly relative to side member  214  of framework  210  of filter assembly  133 .  FIG. 32  illustrates this aspect showing side member  214  of framework  210  of filter assembly  133 , electrical contact  261  mounted to framework  210  at side member  214  of filter assembly  133 , and electrical contact  294  integral with electrical contact  261  projecting outwardly relative to side member  214  of filter assembly  133 . 
     As previously mentioned, when filter apparatus  120  is assembled downstream electrodes  143  of filters of filter assembly  132  are electrically connected to downstream electrodes  143  of filters  140  of filter assembly  133 . Electrical contacts  261  between filter assemblies  132  and  133  provide this electrical connection. In particular, when filter apparatus  120  is assembled filter assemblies  132  and  133  are mounted side-by-side and extend upright and together reside in a common vertical plane, in which side member  215  of filter assembly  132  faces and confronts side member  214  of filter assembly  133  as illustrated in  FIGS. 32 and 31 . Electrical contacts  261 , and electrical contacts  294  integral therewith, between filter assembly  132  and filter assembly  133  relate, whereby electrical contacts  294  of filter assembly  132  contact electrical contacts  294  of filter assembly  133  thereby electrically connecting downstream electrodes  143  of filters  140  of filter assembly  132  to downstream electrodes  143  of filters  140  of filter assembly  133 , in accordance with the principle of the invention. 
     The structural details of ionizer assemblies  130  and  131  and filter assemblies  132  and  133  have been discussed in detail. The balance of this specification relates to the installation and implementation of the assembled filter apparatus  120  with air conditioning system  100  referenced in  FIGS. 1 and 3 . Referring to  FIG. 3 , to install filter apparatus  120  a portion of housing  102  is removed revealing air conditioning apparatus  108  disposed in air flow pathway  109  extending through housing  102  as specified  FIG. 3 . The installation of filter apparatus  120  begins first with the installation of supports  134  and  135  referenced in  FIG. 6 . 
     Supports  134  and  135  are tracks that are attached to housing  102  and which, in turn, receive and hold ionizer assemblies  130  and  131  and filter assemblies  132  and  133  forming filter apparatus  120 . Referring to  FIG. 6 , supports  134  and  135  are substantially coextensive, and are each formed of plastic, polyethylene, or other non-conductive material or combination of non-conductive materials. Support  134  consists of an elongate fixture  330  including a lower surface  331 , an opposed upper surface  332 , and opposed ends  333  and  334 . Formed in upper surface  331  are two, opposed parallel grooves  335  and  336 , which run along the entire length of fixture  330  from end  333  to end  334 . Support  135  consists of an elongate fixture  340  including an upper surface  341 , an opposed lower surface  342 , and opposed ends  343  and  344 . Formed in lower surface  342  are two, opposed parallel grooves  345  and  346 , which run along the entire length of fixture  340  from end  343  to end  344 . Upper and lower members  172  and  173  of frameworks  170  of ionizer assemblies  130  and  131  incorporate elongate tongues  350  and  351 , respectively, which relate to grooves  345  and  335  of supports  340  and  330 , respectively. Upper and lower members  212  and  213  of frameworks  210  of filter assemblies  132  and  133  incorporate elongate tongues  352  and  353 , respectively, which relate to grooves  346  and  336  of supports  340  and  336 , respectively. 
     Looking to  FIG. 36  supports  134  and  135  are mounted interiorly to housing  102  and are directed toward, and reside in, air flow pathway  109  between air conditioning apparatus  108  and inlet  103 . Supports  134  and  135  are spaced upstream of and parallel to air conditioning apparatus  108 . Support  134  is the lower support and is mounted interiorly to the floor  102 A of housing, and support  135  is the upper support and is mounted interiorly to ceiling  102 B of housing  102 . Lower surface  331  of support  134  is flat and is applied against floor  102 A of housing  102 , and is secured in place with adhesive, rivets, screws, or the like. Upper surface  341  of support  135  is flat and is applied against ceiling  102 B of housing  102 , and is secured in place with adhesive, rivets, screws, or the like. At this point, an end plate  360  referenced in  FIGS. 6 and 36  may be affixed between ends  334  and  344  (end  344  not shown in  FIG. 36 ). Having installed supports  134  and  135 , ionizer assemblies  130  and  131  and filter assemblies  132  and  133  may now be installed, in accordance with the principle of the invention. 
     To install ionizer assemblies  130  and  131 , ionizer assembly  131  is taken up and held upright with upstream electrode  151  facing away from air conditioning apparatus  108  toward inlet  103 , ionizer electrodes  150  facing toward air conditioning apparatus  108 , upper member  172  facing lower surface  342  of support  135  and lower member  173  facing upper surface  332  of support  134 . Tongues  350  and  351  are applied to grooves  345  and  335  at ends  343  and  333  of supports  135  and  134 , and ionizer assembly  131  is then simply slide inwardly along supports  135  and  134  until side member  175  is applied against end plate  360  connected between ends  344  and  334  of supports  135  and  134  as illustrated in  FIG. 37 . In  FIG. 37 , electrical contacts  207  electrically connected to upstream electrode  151  of ionizer assembly  131 , and electrical contact  196  electrically connected to ionizer electrodes  150  (not illustrated in  FIG. 37 ) are each illustrated extending away from side member  174  of framework  170  of ionizer assembly  131 . As a matter of illustration,  FIG. 35  illustrates support  134  and ionizer assembly  131  disposed atop upper surface  332  of support  134  as ionizer assembly  131  would appear being slide along support  134  in the installation of filter apparatus  120 . After ionizer assembly  131  is installed, ionizer assembly  130  may then be installed. 
     To install ionizer assembly  130 , ionizer assembly  130  is taken up and held upright with upstream electrode  151  facing away from air conditioning apparatus  108  toward inlet  103 , ionizer electrodes  150  facing toward air conditioning apparatus  108 , upper member  172  facing lower surface  342  of support  135  and lower member  173  facing upper surface  332  of support  134 . Tongues  350  and  351  of ionizer assembly  130  are applied to grooves  345  and  335  at ends  343  and  333  of supports  135  and  134 , and ionizer assembly  130  is then simply slide inwardly along supports  135  and  134  until side member  175  is juxtaposed relative to side member  174  of ionizer assembly  131  and electrical contacts  207  disposed along side member  175  of ionizer assembly  130  engage and thereby electrically contact the corresponding electrical contacts  207  disposed along side member  174  of ionizer assembly  131 , and electrical contact  196  disposed along side member  175  of ionizer assembly  130  engages and thereby electrically contacts the corresponding electrical contact  196  disposed along side member  174  of ionizer assembly  131 . In response to electrical contacts  207  disposed along side member  175  of ionizer assembly  130  engaging and thereby electrically contacting the corresponding electrical contacts  207  disposed along side member  174  of ionizer assembly  131 , upstream electrodes  151  of ionizer assembly  130  is electrically connected to upstream electrode  151  of ionizer assembly  131 , in accordance with the principle of the invention. In response to electrical contact  196  disposed along side member  175  of ionizer assembly  130  engaging and thereby electrically contacting the corresponding electrical contact  196  disposed along side member  174  of ionizer assembly  131 , ionizer electrodes  150  of ionizer assembly  130  are electrically connected to ionizer electrodes  150  and ionizer assembly  131 , in accordance with the principle of the invention. 
     To install filter assemblies  132  and  133 , filter assembly  133  is taken up and held upright with upstream face  141  of filters  140  facing away from air conditioning apparatus  108  toward ionizing electrodes  150  of ionizer assemblies  130  and  131 , downstream electrodes  143  of filters  140  facing toward air conditioning apparatus  108 , upper member  212  facing lower surface  342  of support  135  and lower member  213  facing upper surface  332  of support  134 . Tongues  352  and  353  are applied to grooves  345  and  335  at ends  343  and  333  of supports  135  and  134 , and filter assembly  133  is then simply slide inwardly along supports  135  and  134  until side member  215  is applied against end plate  360  connected between ends  344  and  334  of supports  135  and  134  as illustrated in  FIG. 31 . In  FIG. 31 , electrical contacts  294  electrically connected to downstream electrodes  143  of filter assembly  133  are each illustrated extending away from side member  214  of framework  210  of filter assembly  133 . As a matter of illustration,  FIG. 35  illustrates support  134  and filter assembly  133  disposed atop upper surface  332  of support  134  as filter assembly  133  would appear being slide along support  134  in the installation of filter apparatus  120 . After filter assembly  133  is installed, filter assembly  132  may then be installed. 
     To install filter assembly  132 , filter assembly  132  is taken up and held upright upstream face  141  of filters  140  of filter assembly  132  facing away from air conditioning apparatus  108  toward ionizing electrodes  150  of ionizer assemblies  130  and  131 , downstream electrodes  143  of filters  140  of filter assembly  132  facing toward air conditioning apparatus  108 , upper member  212  facing lower surface  342  of support  135  and lower member  213  facing upper surface  332  of support  134 . Tongues  352  and  353  of filter assembly  132  are applied to grooves  345  and  335  at ends  343  and  333  of supports  135  and  134 , and filter assembly  132  is then simply slide inwardly along supports  135  and  134  toward filter assembly  133  until side member  215  is juxtaposed relative to side member  214  of filter assembly  133  and electrical contacts  294  disposed along side member  215  of filter assembly  132  engage and thereby electrically contact the corresponding electrical contacts  294  disposed along side member  214  of filter assembly  133 . In response to electrical contacts  294  disposed along side member  215  of filter assembly  132  engaging and thereby electrically contacting the corresponding electrical contacts  294  disposed along side member  214  of filter assembly  133 , downstream electrodes  143  of filter assembly  132  are electrically connected to downstream electrodes  143  of filter assembly  133 , in accordance with the principle of the invention. Upon installation of ionizer assemblies  130  and  131  and filter assemblies  132  and  133  with respect to supports  134  and  135  as herein explained, filter apparatus  120  is formed and installed in air flow pathway  109  as illustrated in  FIG. 4  between inlet  103  and air conditioning apparatus  108  (not shown in  FIG. 4 ). At this point, end plate  361  may be secured to side members  174  and  214  of ionizer and filter assemblies  130  and  132 , respectively as illustrated in  FIG. 8 . After making the required electrical connections grounding downstream electrodes  143  of filter assemblies  132  and  133 , and electrically connecting ionizer electrodes  150  of ionizer assemblies  130  and  131  to a direct current power supply for supplying the required potential to ionizer electrodes  150  of ionizer assemblies  130  and  131 , cover  110  referenced in  FIG. 2  may be secured to housing  102  completing the installation of filter apparatus  120 . 
     Upon completion of the installation of ionizer assemblies  130  and  131  and filter assemblies  132  and  133  as herein described, ionizer assemblies  130  and  131  are mounted side-by-side relative to air stream A passing along air flow pathway  109 , filter assemblies  132  and  133  are mounted side-by-side relative to air stream A passing through air flow pathway  109  opposing and downstream of ionizer assemblies  130  and  131 , ionizer electrodes  150  of ionizer assembly  130  are electrically connected to ionizer electrodes  150  of ionizer assembly  131 , upstream electrode  151  of ionizer assembly  130  is electrically connected to ionizer electrode  151  of ionizer assembly  131 , and downstream electrodes  143  of filters  140  of filter assembly  132  are electrically connected to downstream electrodes  143  of filters  140  of filter assembly  133 . Ionizer assemblies  130  and  131  extend upright and together reside in a common vertical plane, and filter assemblies  132  and  133  are upright and together reside in a common vertical plane opposing and parallel to the common vertical plane in which ionizer assemblies  130  and  131  reside. The vertical planes defined by ionizer assemblies  130  and  131 , and filter assemblies  132  and  133  are substantially perpendicular relative to oncoming air stream A which flows first through ionizer assemblies  130  and  131  and then through filter assemblies  132  and  133 . 
     As previously discussed, and which is again discussed here for clarity, ionizer assemblies  130  and  131  each supportionizer electrodes  150 , and an upstream electrode  151 . Ionizer electrodes  150  are supported in a common vertical plane denoted at P 2  in  FIG. 2  in air stream A upstream of, and parallel to, upstream face  141  of filters  140  and plane P 1  defined by downstream electrodes  143 . Ionizer electrodes  150  are substantially equally sized and identical in structure, the details of which will be discussed later in this specification. Ionizer electrodes  150  of ionizer assembly  130  are electrically connected, ionizer electrodes  150  of ionizer assembly  131  are electrically connected, and ionizer electrodes  150  of ionizer assembly  130  are electrically connected to ionizer electrodes  150  of ionizer assembly  131 . It is to be understood that upstream electrodes  151  of ionizer assemblies  130  and  131  are supported in vertical plane denoted at P 3 , ionizer electrodes  150  of ionizer assemblies  130  and  131  are supported in vertical plane P 2 , and downstream electrodes  143  of filters  140  of filter assemblies  132  and  133  are supported in vertical plane P 1 . Planes P 1 -P 3  are parallel relative to each other and preferably to air conditioning apparatus  108 , whereby distance D 1  separates plane P 3  from plane P 2 , and distance D 2  separates plane P 2  from plane P 1 . 
     In operation, and with reference to  FIG. 8 , a potential is applied to ionizer electrodes  150  of ionizer assemblies  130  and  131 . The potential applied to ionizer electrodes  150  imparts through induction a potential to upstream electrodes  151  of ionizer assemblies  130  and  131  forming ionizing field  160  between upstream electrodes  151  and ionizer electrodes  150  in juxtaposition along upstream electrodes  151 , and a potential to downstream electrodes  143  forming ionizing field  161  between downstream electrodes  143  and ionizer electrodes  150  in juxtaposition along downstream electrodes  143 . The engagement of each downstream electrode  143  against a corresponding filter  140  imparts ionizing field  161  to filters  140  and maintains ionizing field  161  with filters  140 , according to the principle of the invention. 
     The potential applied to ionizing electrodes  150  is substantially uniformly dispersed across ionizer electrodes  150  of ionizer assemblies  130  and  131  because, as herein described, ionizer electrodes  150  of ionizer assembly  130  are electrically connected, ionizer electrodes  150  of ionizer assembly  131  are electrically connected, and ionizer electrodes  150  of ionizer assemblies  130  and  131  are electrically connected. Moreover, the induced potential formed in upstream electrodes  151  of ionizer assemblies  130  and  131  is also substantially uniformly dispersed across upstream electrodes  151  because upstream electrodes  151  of ionizer assemblies  130  and  131  are electrically connected as herein described. Because the potential applied to ionizer electrodes  150  is substantially uniformly dispersed across ionizer electrodes  150  and because the induced potential across upstream electrodes  151  is also substantially uniformly dispersed across upstream electrodes  151 , ionizing field  160  formed along upstream electrodes  151  between upstream electrodes  151  and ionizer electrodes  150  is, thereby, substantially uniform, in accordance with the principle of the invention. 
     Again, the induced potential formed in downstream electrodes  143  is substantially uniformly dispersed across downstream electrodes  143  of filters  140  of filter assemblies  132  and  133  because, as herein specifically described, downstream electrodes  143  of filter assembly  132  are electrically connected, downstream electrodes  143  of filter assembly  133  are electrically connected, and downstream electrodes  143  of filter assembly  132  are electrically connected to downstream electrodes  143  of filter assembly  133 . Because the potential applied to ionizer electrodes  150  is substantially uniformly dispersed across ionizer electrodes  150 , as discussed above, and because the induced potential across downstream electrodes  143  is also substantially uniformly dispersed across downstream electrodes  143 , ionizing field  161  formed along downstream electrodes  143  between downstream electrodes  143  and ionizer electrodes  150  is, thereby, substantially uniform. 
     Again, the potential across ionizer electrodes  150  is positive, and the potentials across upstream electrodes  151  and downstream electrodes  143  are each also positive but lesser in magnitude in comparison to the potential across ionizer electrodes  150 . Because the positive potentials across upstream electrodes  151  and downstream electrodes  143  are each lesser in magnitude than the positive potential applied across ionizer electrodes  150 , upstream electrodes  151  and downstream electrodes  143  are net negatively charged as compared to the potential across ionizer electrodes  150 . 
     Through induction, positively charged electrons flow or otherwise migrate from ionizer electrodes  150  across distance D 1  to upstream electrodes  151  and to downstream electrodes  143 , thereby forming the induced potential in upstream electrodes  151  and the induced potential in downstream electrodes  143 , according to the principle of the invention. As the positively charged electrons generated by ionizer electrodes  150  reach upstream electrodes  151  and induce the potential in upstream electrodes  151 , ionizing field  160  is formed along upstream electrodes  151  between upstream electrodes  151  and ionizer electrodes  150 . Ionizing field  160  is positive, but is lesser in magnitude in comparison to the potential across ionizer electrodes  150  and therefore has a net negative charge as compared to the potential across ionizer electrodes  150 . As the positively charged electrons generated by ionizer electrodes  150  reach downstream electrodes  143  and induce the potential in downstream electrodes  143 , ionizing field  161  is formed along downstream electrodes  143  between downstream electrodes  143  and ionizer electrodes  150 . Ionizing field  161  is positive, but is lesser in magnitude in comparison to the potential across ionizer electrodes  150  and therefore has a net negative charge as compared to the potential across ionizer electrodes  150 . According to the principle of the invention as previously indicated, the contact or engagement of each downstream electrode  143  against a corresponding filter  140  imparts and maintains ionizing field  161  in filters  140 , thereby imparting or otherwise inducing a positive charge to filters  54 , which is lesser in magnitude than the positive charge across ionizer electrode  55 . 
     Air stream A passes through filter apparatus  120  along air flow pathway  109  from inlet in a direction from upstream electrodes  151  of ionizer assemblies  130  and  131  to downstream electrodes  143  of filter assemblies  132  and  133  and then to air conditioning apparatus  108 . As air stream A passes through filter apparatus  120 , air stream A passes first through upstream electrodes  151  and then through ionizing field  160 . As particles conveyed by air stream A, such as dust particles, mold particles, microbial particles, smoke particles, and other air-borne particles, encounter ionizing field  160 , ionizing field  160  imparts or otherwise induces a potential or electric charge to the particles suspended in air stream A causing the particles to become attracted to each other forming clusters of the particles, which are then conveyed by air stream A downstream through ionizer electrodes  150  to filters  143 , which entraps the clusters of particles thereby removing the clusters of particles from air stream A. The clusters of particles formed by the interaction of the particles with ionizing field  160  are positively charged. The positive charge to the clusters is imparted to the clusters by ionizing field  160 , and is lesser in magnitude than the positive charge of ionizing field  161  applied across filters  140 . Accordingly, as the clusters of particles reach filters  140 , the net negative charge applied to the clusters as compared to the net positive charge applied across filters  140  by ionizing field  161  causes the clusters to be electrically attracted to filters  140  thereby producing an aggressive and comprehensive removal of the clusters of particles from air stream A by filters  140  and a highly efficient and effective filtration efficiency, according to the principle of the invention. 
     When particles pass through ionizing field  160 , not only do the particles become attracted to one another to form clusters, a churning motion caused by the Van Der Walls Effect is imparted to the particles, which helps the particles impact one another and group together to form clusters of particles. The potential imparted to filters  140  by ionizing field  161  attracts and adheres the clusters of particles to filters  140 , according to the principle of the invention. 
     Ionizer electrodes  150  are energized by a high voltage direct current power supply  400  illustrated in  FIG. 5 . Preferably, ionizer electrodes  150  are electrically connected to a power supply  400  before cover  110  is attached to enclose housing  102  after the installation of filter apparatus  120 . In the present embodiment, plug  200 , illustrated in  FIGS. 4 and 37 , is electrically connected to receive power from power supply  400 , whereby plug  200  conveys the supplied power to ionizer electrodes  150  via supply wires  201  and  202  of ionizer assemblies  130  and  131 . A plug  401 A of electrical wiring  401  is electrically connected to plug  200  thereby electrically connecting power supply  400  to plug  200 , which is referenced in  FIGS. 4 and 37 . The electrical connection of plug  200  to power supply  400  is made before cover  110  is applied to enclose the installed filter apparatus  120  in air flow pathway  109  through housing  102 . When energized, power supply  400  imparts a potential, namely, a positive potential, to ionizer electrodes  150  of ionizer assemblies  130  and  131 . 
     In the present embodiment, power supply  400  is disposed exteriorly of air flow pathway  109 , and is mounted in housing  122  forming part of control system  121 . As seen in  FIG. 2 , control system  121  including housing  122  is mounted to a large duct coupling the interior of building an air communication with inlet  103  leading to air flow pathway  109  through housing  102 , although control system  121  may be mounted at any suitable location. Power supply  400  supplies ionizer electrodes  150  of ionizer assemblies  130  and  131  with power and thereby controls the operation of filter apparatus  120 . 
     Power supply  400  is an AC to DC high voltage power supply, which provides high voltage to ionizer electrodes  150  of ionizer assemblies  130  and  131  forming the potential thereacross. For filter apparatus  120  to operate according to desired specifications as disclosed herein, preferably power supply  400  provides a voltage of approximately 14-30 KVDC, with a preferred operating voltage being approximately 15.5 KVDC. Again, because ionizer electrodes  150  of ionizer assemblies  130  and  131  are electrically connected, the potential applied to ionizer electrodes  150  of ionizer assemblies  130  and  131  from power supply  400  is substantially uniformly dispersed across ionizer electrodes  150  of ionizer assemblies  130  and  131 . Based on the operating voltage range provided by power supply  400 , distance D 1  between ionizer electrodes  150  and upstream electrodes  151  is preferably 1-3 inches, with a preferred distance D 1  being approximately 1.8 inches based on the preferred operating voltage of approximately 15.5 KVDC. Distance D 2  between ionizer electrodes  150  and downstream electrode  143  is not overly critical to the function of filter apparatus  120  according to the structure of filter apparatus  120  herein disclosed. According to the preferred embodiment disclosed herein, distance D 2  is preferably is approximately 5-10 inches. 
     As previously explained, the magnitude of ionizing fields  160  and  161  is determined principally by the voltage provided by power supply  400  across ionizer electrodes  150 , in addition to the magnitude of distances D 1  and D 2 . Accordingly, the operating or filtering characteristics may be selectively determined by selecting the power applied by power supply  400 . The selected intensity of ionizing fields  160  and  161 , and more importantly ionizing field  160 , is largely dependent on specific needs and applications. 
     Downstream electrodes  143  are preferably grounded, preferably before cover  110  is attached to enclose housing  102  after the installation of filter apparatus  120 . Downstream electrodes  143  may be grounded directly to an earth ground and/or to the negative side of power supply  400 . As a matter of example, a plug  277  of ground electrical wiring  275 A ( FIG. 37 ) is plugged into plug  276  wired to proximal ends  270  of electrical contacts  260  of filter assembly  132  and the negative side of power supply  400  as illustrated in  FIG. 5 , which provides the grounding of downstream electrodes  143  of filter assemblies  132  and  133 . The electrical connection grounding downstream electrodes  143  is made before cover  110  is applied to enclose the installed filter apparatus  120  in air flow pathway  109  through housing  102 . 
     At a fixed or predetermined voltage of power supply  400  as previously mentioned, the operating or filtering characteristics of filter apparatus  120  may be determined by selecting the voltage applied by power supply  400 . Again, the selected intensity of ionizing fields  60  and  61 , and more importantly ionizing field  60 , is largely dependent on specific needs and applications. Alternatively, power supply  400  may be a variable voltage power supply, in which the applied voltage may be increased or decreased so as to maintain the same level of current across filter apparatus  120 . The voltage provided by power supply  400  across ionizer electrodes  150  may be required to float up or down depending on the loading of filters  140  over time, as well as independent factors such as humidity and/or temperature so as to maintain the predetermined current level across filter apparatus  120 . This predetermined level of current is directly proportional to the effectiveness of filter apparatus  120  and may require the voltage to be floating and variable according to a various factors that may impact the operational characteristics of filter apparatus  120 . 
     In a particular embodiment, upstream electrodes  151  are connected to a resistor used to control the induced potential applied across upstream electrodes for reducing the incidence of arcing and to reduce excess production of ozone. Upstream electrodes  151  are electrically connected to a resistor, preferably before cover  110  is attached to enclose housing  102  after the installation of filter apparatus  120 .  FIG. 8  illustrates an electrical plug  405 , such as a banana plug or other suitable electrical plug, formed in side member  174  of framework  210  of ionizer assembly  130 , which is electrically connected to upstream electrode  151  of ionizer assembly  140  with a wire  406 . Plug  405  is, in turn, electrically coupled to a corresponding plug  409  that, in turn, is coupled to a resistor  407  mounted in housing  122  with electrical wire  408 . Resistor  407  is grounded and may be set to a predetermined voltage value to achieve a selected magnitude of the potential across upstream electrodes  151  of ionizer assemblies  130  and  131  and thus a selected magnitude of ionizing field  160 . Resistor  407  may be set to any selected voltage value for establishing a selected magnitude of the potential across upstream electrodes  151  of ionizer assemblies  130  and  131  for establishing a selected magnitude of ionizing field  160  and for reducing arcing and for reducing excess production of ozone. 
     Those having regard for the art will readily appreciate that a highly efficient modular electrically stimulated air filter apparatus is disclosed, which is easy to construct, easy to assemble, and easy to install in conjunction with a large-scale air conditioning system as herein described. Although filter apparatus  120  is discussed herein in connection with a 20-ton air conditioning apparatus  108 , filter apparatus  120  may be employed in connection with air conditioning systems of varying sizes. Furthermore, the various elements of filter apparatus  120  may be scaled or multiplied as needed for meeting specific needs. For instance, although filter apparatus  120  incorporates two ionizer assemblies  130  and  131 , less or more may be utilized. Although filter apparatus  120  incorporates two filter assemblies  132  and  133 , less or more may be utilized. Furthermore, although filter assemblies  132  and  133  each utilize four filters  140 , less ore more may be utilized. Still further, the sizes of the various components of the invention may be selected for meeting any desired need or implementation. To ensure complete air filtering, strips  256  of foam rubber may be applied to frameworks  170  and  210  of ionizer assemblies  130  and  131  and filter assemblies  132  and  133  for interacting between frameworks  170  of ionizer assemblies  130  and  131  for preventing air from flowing therebetween, for interacting between frameworks  210  of filter assemblies  132  and  133  for preventing air from flowing therebetween, for interacting between frameworks  170  of ionizer assemblies  130  and  131  for preventing air from flowing between frameworks  170  and supports  134  and  135  and also end plates  360  and  361 , and for interacting between frameworks  210  of filter assemblies  132  and  133  for preventing air from flowing between frameworks  210  and supports  134  and  135  and also end plates  360  and  361 . Strips  256  of foam rubber may be applied between ionizer assemblies  130  and  131 , between filter assemblies  132  and  133 , and between assemblies  130 - 133  and supports  145  and  134  and end plates  360  and  360  in any desired manner for limiting air flow along the regions of the applied strips  256  of foam rubber. Strips  256  of foam rubber are referenced throughout the various figures for illustration and reference. 
     Filter apparatus  120  is exemplary for removing particles from air stream A upstream of air conditioning apparatus  108  for providing clean, conditioned air to the interior spaces of a building. The particles filter apparatus  120  can remove include such particles as dust particles, mold particles, microbial particles, smoke particles, and other air-borne particles. Ionizer assemblies  130  and  131  and filter assemblies  132  and  133  are easy to construct offsite, easy to transport to a given installation, and easy to install in connection with an existing large-scale air conditioning system as herein discussed. Filter apparatus  120  is useful in that filter apparatus  120  provides for the efficient and exemplary removal of particles from an air stream, provides for the suppression of odors in odoriferous air caused by particles that impart undesired odors, such as air contaminated with cigarette smoke, and is capable of removing particles such as germs and other microbial agents from an air stream, including contagious airborne pathogen particles, legionella particles, sars particles,  bacillus subtilis  particles,  serratia merescens  particles,  aspergillus versicolor  particles, etc. Also, tests conducted with filter apparatus  120  show that exposure of germs and microbial particles, such as  bacillus subtilis, serratia merescens, aspergillus versicolor , and the like, trapped in filters  140  to the electrostatic fields generated by filter apparatus  120  kill or otherwise neutralize such particles, according to the principle of the invention. 
     In the preferred embodiment herein described, ionizer assemblies  130  and  131  extend upright and together reside in a common vertical plane, and filter assemblies  132  and  133  are upright and together reside in a common vertical plane opposing and parallel to the common vertical plane in which ionizer assemblies  130  and  131  reside. It is to be understood that ionizer assemblies  130  and  131  and filter assemblies  132  and  133 , which together form filter apparatus  120 , may be disposed substantially horizontally or at other selected angle relating to an oncoming air stream without departing from the invention. 
     The invention has been described above with reference to a preferred embodiment. However, those skilled in the art will recognize that changes and modifications may be made to the embodiment without departing from the nature and scope of the invention. Various changes and modifications to the embodiment herein chosen for purposes of illustration will readily occur to those skilled in the art. To the extent that such modifications and variations do not depart from the spirit of the invention, they are intended to be included within the scope thereof. 
     Having fully described the invention in such clear and concise terms as to enable those skilled in the art to understand and practice the same, the invention claimed is: