Patent Publication Number: US-2022233983-A1

Title: Multi-Piece HVAC Air Filter Housing, Filter Assembly And Methods

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This US utility patent application claims priority benefit to U.S. provisional patent application Ser. No. 63/140,368 filed Jan. 22, 2021, the entire contents of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to air filter devices for heating, ventilation and air conditioning (HVAC) systems and other forced air flow products and devices. 
     BACKGROUND 
     Air quality inside of commercial and residential buildings has long been important and a priority to providing a healthy work or living environment for occupants. With the rise of a world-wide viral pandemic which easily spreads through the air, healthy air quality is increasingly important in commercial buildings where large numbers of occupants work in close proximity and spend a significant amount of time in the enclosed environment. In other commercial buildings, for example municipal and federal office buildings, law enforcement and defense facilities, public and private schools, retail stores, restaurants and other services establishments, a high volume of daily foot or people traffic enter and exit the buildings each day which increases the opportunity to compromise the air quality. 
     Conventional air filters used in large commercial buildings are typically positioned in large heating, ventilation and air conditioning (HVAC) systems on the roofs of the buildings near the fan blower motors which are out of sight of the occupants and require service or maintenance by professionals or building maintenance staff. As these filters are out of sight, there is a tendency or likelihood that the filters will not be maintained or replaced regularly or as recommended by the filter manufacturers. There is further a concern with these conventional HVAC systems in that since the filter media is positioned at the front or upstream end of the air flow path, the filters may unduly restrict the air flow into the working spaces and/or cause the large blower motors to work harder to maintain circulation causing premature wear of the costly circulation motors and other system components. Another disadvantage to conventional HVAC systems is that inevitably over time, dust and other air debris or particles accumulate on the visible exhaust vents which are largely overlooked by typical cleaning procedures. These dusty, partially clogged vents are unsightly and further the opportunity for germs or other unhealthy conditions to develop negatively impacting air quality. 
     Other conventional air filter devices have been used on the interior of commercial or residential buildings. In commercial buildings with suspended ceilings, conventional devices have been placed above the suspended ceilings, out of sight of occupants and maintenance personnel, and are subject to the same disadvantages as the roof top filtration systems discussed above. Other conventional air filter devices include a housing or frame which holds a filter media have been used to attach to the floor or wall vent or louver structures and extend into the working or living space. These devices suffer from significant disadvantages of not being able to be used with high quality commercially-available filter cartridges needed for high air quality. These devices further have been designed to be large, single piece structures which are not economical to ship or store in large quantities. Due to the single-piece, often irregular sized components, low quantities can be packaged in boxes for shipment which reduces efficiency and increases costs to manufacturers. Once onsite, the conventional and/or single piece frames or components take up a large amount of storage space which is often very limited. 
     There is a need in conventional air filter devices and systems to resolve or greatly improve on these many disadvantages. There is a further need to provide an air filter device and method which is easy to use and maintain, economical to manufacture, transport and store, and that is visible to occupants to provide a level of confidence in air quality and health security, and that improves air filtration and air quality in working and living spaces. 
     SUMMARY 
     Disclosed herein is a multi-piece filter housing, filter assembly, and methods of assembly and installation useful in forced-air HVAC systems and other forced-air or air circulation devices. The invention is particularly, but not exclusively, useful in commercial buildings with common suspended ceilings with forced air passage openings or vents which exhaust or blow air into, or remove air from, interior working spaces. The air filter housing, and in the form of an air filter assembly, is operable to accept commercially-available, standard-sized, high quality air filter media or cartridges and easily connects to the suspended ceiling support grid around the forced-air passage opening extending into the working space. The invention is also useful in many other applications including residential HVAC systems and other forced-air products or devices, for example standalone electric circulation fans commonly used in residential and commercial spaces. 
     In one example of the invention, a multi-piece air filter housing includes at least a first sidewall section and a second sidewall section each including a sidewall having a first end and a second end, an upper end, and a lower end and a filter media stop connected to at least one of the first sidewall section or the second sidewall section. A sidewall connector is operable to connect the at least first sidewall and the second sidewall together which define an interior cavity for receipt of the air filter media. The sidewall connector allows easy and secure connection of the first sidewall section and the second sidewall section together forming a rigid, or substantially rigid, air filter housing. A housing connector is used to secure the connected first sidewall section and the second sidewall section circumferentially around a forced-air passage opening. 
     In one example, the filter media stop is connected to each of the first sidewall section and the second sidewall section which extends inward from the sidewalls providing a support surface for the air filter media positioned in the interior cavity. Once an air filter media is installed in the interior cavity of the housing, the filter media stop supports the air filter media to direct forced-air passing through the air filter media either into a working space, or removing air from the working space. 
     In one example, the at least first sidewall section and the second sidewall section include a total of four modular sidewall sections of the same, or substantially the same, configuration, including a first sidewall section, a second sidewall section, a third sidewall section, and a fourth sidewall section. Each sidewall section having a sidewall including the first end and the second end, the upper end and the lower end, the filter media stop, the sidewall connector (to connect the four sidewall sections together to form the air filter housing and interior cavity), and the housing connector (to connect the assembled air filter housing and installed filter media around the forced air passage opening). The four modular sidewall sections when connected, form the rigid or substantially rigid air filter housing. When the four sidewall sections are not connected together, the four modular sidewall sections are highly compact and efficient to manufacture, ship, and store in contrast to conventional air filter housings and air filter assemblies described above, for example single piece frames or housings. In the field, the four modular sidewall sections are easily assembled to form the air filter housing, receive the air filter media, and be installed. 
     In one example, the sidewall connectors are integral with the sidewall sections and include a first sidewall connector and a complimentary second sidewall connector. In one example the first sidewall connector is an elongate angled tab on the first end of the sidewall, and the second sidewall connector is a complimentary elongate angled channel defining an angled slot on the second end of the sidewall. The complimentary angled tab and angled slot allow for secure, sliding and frictional engagement of the sidewall sections to form the interior cavity for receipt of the air filter media. 
     In one example, the filter media stop includes a lower flange extending inward from the lower end of the sidewall and defines a housing air passage opening allowing forced air to pass through the filter media and through the housing air passage opening into the working space. Alternately, in a forced air return example, the drawn air passes through the housing air passage opening and the through the filter media. In one example, the housing air passage opening is defined by distal ends of the lower flanges and is unobstructed by the air filter housing between the lower flange distal ends allowing substantially all of the filter media to be visibly seen through the housing air passage opening from the working space. 
     In one example, the at least first and second sidewall sections also include an upper flange that extends outward from the sidewalls. In one example, the housing connector is a plurality of magnets that are connected to the upper flange. In one example, the forced-air passage opening is defined by a frame including a suspended ceiling support grid made from a ferrous metal material. The magnets provide a removable but secure connection for the air filter housing, or air filter assembly including the installed air filter media, to the suspended ceiling support grid circumferentially surrounding the HVAC forced-air passage opening or vent. In one example, a seal is connected to the upper flange which is operable to further direct the forced-air to pass through the air filter media, and through the housing air passage opening. 
     In one example of an air filter assembly, the air filter housing is operable to receive the air filter media in an interior cavity of the air filter housing. A housing connector is used to secure the air filter housing and installed air filter media circumferentially around the forced-air passage opening. In one example, the air filter media consists of a standard-sized, high quality, commercially-available air filter cartridge that is easily installed in the assembled air filter housing and replaced when needed. 
     In an exemplary method for assembling an air filter housing, at least a first sidewall section and a second sidewall section are provided which each include a sidewall having a first end, a second end, an upper end, a lower end, and a filter media stop. In one example four modular sidewall sections are used including these same features. A sidewall connector is aligned with the at least first sidewall section and the second sidewall section and is used to connect the first sidewall section and second sidewall section together defining the interior cavity operable to receive an air filter media. In one example, a housing connector is attached to the assembled air filter housing and is operable to connect the assembled air filter housing (and when installed, a filter media) around a forced air passage opening to filter the air flow. 
     In one example of a method for installing an air filter assembly, the air filter housing is assembled by connecting the at least first sidewall section and the second sidewall section together through use of the sidewall connectors. In one example, the air filter housing includes four modular sidewall sections including integral sidewall connectors. An air filter media or cartridge is installed in the assembled air filter housing interior cavity and the air filter housing and installed air filter media is positioned circumferentially around a forced air passage opening. The housing connector is used to connect the air filter assembly around the forced air passage opening. In one example, the forced air passage opening is in a suspended ceiling and defined by a frame of a suspended ceiling support grid. 
     The inventions described herein provide numerous and significant advantages over conventional air filter housings and air filter assembly designs. The multi-piece air filter housing with connecting sidewall sections minimizes the space needed for shipping and storage in all stages of manufacturing and in the field, while providing a rigid structure and an interior cavity for receipt of high quality, commercial-grade, commonly available air filter media for improved air quality. The design of the sidewall sections provides for easy assembly (and disassembly) with minimal, or reduced, air leakage. Use in the form of an air filter assembly with a commercial-grade air filter media cartridge has shown to provide significant improvements in filtered air quality in working and living spaces. In one application, the inventive air filter housing and air filter assembly provides for easy, secure, and removable connection to a suspended ceiling or forced-air opening frame while providing easy access to the filter media for replacement. The inventive air filter housing and installed air filter media provide high visibility of the air filter media through the housing air passage opening which is unobstructed by the housing itself providing comfort and peace of mind for building occupants as well as easy visibility of substantially all of the air filter media from within the working space to indicate when an air filter cartridge needs to be replaced. The inventive air filter housing is also very economical to manufacture, and easy to use and maintain in the field by building occupants without particular HVAC experience or a need for tools. 
     These and other aspects of the present disclosure are disclosed in the following detailed description of the embodiments, the appended claims, and the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is best understood from the following detailed description when read in conjunction with the accompanying drawings. It is emphasized that, according to common practice, the various features of the drawings are not to-scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. 
         FIG. 1  is an exploded perspective view of one example of an air filter assembly including an air filter housing and air filter media cartridge in an exemplary application with a suspended ceiling HVAC exhaust vent. 
         FIG. 2  is a top perspective view of the air filter housing shown in  FIG. 1 . 
         FIG. 3  is a top perspective view of the air filter housing in  FIG. 2  shown with an installed exemplary air filter media cartridge. 
         FIG. 4  is a bottom perspective view of the air filter housing of  FIG. 3 . 
         FIG. 5  is a bottom perspective view of the air filter housing shown in  FIG. 2 . 
         FIG. 6  is an exploded perspective view of the air filter housing shown in  FIG. 5  showing two of the sidewall sections disassembled from the remaining two sidewall sections. 
         FIG. 7  is a bottom outer perspective view of an example of the air filter housing sidewall section shown in  FIG. 5 . 
         FIG. 8  is a bottom inner perspective view of the air filter housing sidewall section shown in  FIG. 7 . 
         FIG. 9  is a top view of the inverted sidewall section shown in  FIG. 7 . 
         FIG. 10  is an enlarged view of a portion of  FIG. 9  identified as “A.” 
         FIG. 10A  is a rotated left end view of the sidewall section in  FIG. 7 . 
         FIG. 10B  is a rear view taken in the direction of C of the sidewall section in  FIG. 10A . 
         FIG. 11  is an enlarged view of a portion of  FIG. 9  identified as “B.” 
         FIG. 11A  is a rotated rear perspective view taken in the direction of D of a portion of the sidewall section in  FIG. 8 . 
         FIG. 12  is an enlarged perspective view of a portion of  FIG. 2 . 
         FIG. 13  is a bottom perspective view of a portion of  FIG. 12 . 
         FIG. 14  is an inner perspective view of  FIG. 12 . 
         FIG. 15  is an outer front view of an example of the air filter housing sidewall section. 
         FIG. 16  is an enlarged right side view of  FIG. 15 . 
         FIG. 17  is an enlarged perspective view of an example of a housing connector including a recessed socket shown with an installed magnet (in phantom line). 
         FIGS. 18A-18E  are schematic, alternate example configurations of an air filter housing and sidewall sections. 
         FIG. 19  is a schematic flow chart of an example of a method for assembling a multi-piece air filter housing. 
         FIG. 20  is a schematic flow chart of an example of a method for installing an air filter assembly. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1-20 , examples of an air filter housing, an air filter assembly, and methods of assembly and installation are shown. The exemplary air filter housing, air filter assembly, and methods of assembly and installation are useful for a wide variety of applications where a forced-air HVAC system or device is used to circulate air into, or from, a working or living space, for example the interior of a commercial office building or structure, as well as residential structures. Examples of the invention may also be used on forced air devices, for example stand-alone electric air circulation fans, for example square or box-shaped circulation fans, used to circulate air into or around the interior of commercial or residential spaces. A particularly useful, but not exclusive, application of the invention is in the interior of a commercial office building or structure that includes a suspended ceiling supported by a metallic or ferrous material grid structure and exhaust vents common in most office buildings. There are numerous additional applications where an air filter is desired to increase the air quality in a working or living space known by those skilled in the art. 
     Referring to  FIG. 1  an example of the inventive air filter assembly  10  is shown. The air filter assembly  10  includes a multi-piece air filter housing  14  (shown assembled) and an insertable air filter media  18  (shown in the exemplary form of a commercially-available air filter cartridge  20 ). In the form of an air filter assembly  10 , the exemplary housing  14  with inserted filter media  18  are removably connected to a suspended ceiling  24  (shown in dashed line in  FIG. 1 ) circumferentially around a forced-air passage opening  26  as further discussed below. 
     Exemplary application suspended ceiling  24  includes a plurality of forced-air passage through openings  26  (one shown) defined by an air passage frame or support grid  28  which generally defines or surrounds the forced-air passage opening  26 . In one example, the frame  28  is a support frame or grid commonly used to support suspended ceiling tiles or panels, and is made from a ferrous metal material, or a ferrous or iron-infused material, which is engageable by permanent magnets. The air passage openings  26  are in communication with a HVAC forced air circulation system operable to forcibly generate an air flow  30  into a working or living space  32 . In the example suspended ceiling  24  application shown, the air passage openings  26  extend in a coordinate horizontal X-direction  34  and Y-direction  36 , and the air flow  30  generally passes through the air passage opening  26  along a vertical Z-direction  38  (e.g., downward into the working space  32  for an exhaust vent or upward toward the air passage opening  26  for an air return or intake vent). It is understood that frame  28  may be on structures other than suspended ceilings, for example the square frame of an electric box-type circulation fan, the frame of an exhaust vent of a portable air conditioner, and other forced air devices known by those skilled in the art. 
     It is understood that the described suspended ceiling  24  air passage through openings  26 , and frame  28  may take different sizes, constructions, configurations, geometries, and orientations as known by those skilled in the art. It is also understood that although air flow  30  is shown in one application as flowing through the air passage opening  26  downward into the working space  32 , air flow  30  may also act to in the opposite or upward Z-direction  38  (not shown), for example as a cold air return removing air from the working space  32 . It is further understood that coordinate directions X  34 , Y  36  and Z  38  can take other orientations, for example where air filter assembly  10  and housing  14  are connected to an air passage opening  26  positioned through a vertically-oriented wall or other angled surface (not shown). 
     Referring to  FIG. 2 , an example of the inventive multi-piece air filter housing  14  is shown assembled without a filter media  18  installed. As assembled, the housing  14  is operable to receive and support a filter media  18 , for example an air filter cartridge  20 , and be connected to an air passage opening frame  28  ( FIG. 1 ) for filtering air produced by a forced air source, for example a HVAC system shown in  FIG. 1 , an electric circulation fan, or other forced air source device. Referring to  FIGS. 3 and 4 , the assembled air filter housing  14  is shown with a filter media  18  in the form of installed filter cartridge  20  forms the air filter assembly  10 . 
     Referring to  FIGS. 2 and 5-8 , an exemplary multi-piece air filter housing  14  is shown in an assembled state ( FIGS. 2 and 5 ) and a disassembled state ( FIG. 6 ). It is noted that in  FIGS. 5-8 , the upper end of the housing  14  (for example toward upper flange  70 ) which receives the filter media  18 , which is normally oriented to face upward when in use (as shown in  FIG. 1 ) is illustrated positioned or facing downward. As best seen in  FIG. 5 , housing  14  includes a multi-piece design (four pieces shown) which includes at least a first sidewall section  44  (two shown) and a second sidewall section  44 A (two shown). 
     In one example of housing  14 , the housing  14  includes only two sidewall sections  44  and  44 A. In this example, each of the first sidewall section  44  and the second sidewall section  44 A include two integral portions or pieces, for example each portion forming a 90 degree angle. In the two-piece example, the first sidewall section  44  is a single, integral piece or sidewall section (i.e., the two adjacent sidewall sections  46  (the two 44 pieces) forming a 90 degree angle are molded as a single, integral piece  44 ), and the second sidewall section  44 A is a single, integral piece or sidewall section (i.e., two adjacent sidewall sections  46  molded or formed as a single, integral piece  44 A forming a 90 degree angle as described for first sidewall section  44 ). In other words, in the example housing  14  having at least a first sidewall section  44  and a second sidewall section  44 A, the multi-piece housing  14  includes a total of two sidewall sections ( 44  and  44 A) which are connected together as further described below to form the housing  14  defining an interior cavity  68  for receipt and support of the filter media  18 . Alternate examples of a housing  14  including only two sidewall sections  46  are shown in  FIGS. 18A, 18B, and 18C . 
     In a particularly useful, but not exclusive, example of air filter housing  14  shown in  FIGS. 1-8 , air filter housing  14  includes four separate, modular sidewall sections  46  each having the same construction or configuration as further discussed and illustrated below (i.e., housing  14  includes four separate and independent sidewall sections  46  which are connected together to form housing  14  and define the interior cavity  68  to receive and support the filter media  18 ). For purposes of simplicity alone, housing  14  will be described and illustrated in the example of four modular sidewall sections  46 , although it is understood that housing  14  can alternately be a two-piece design including a first sidewall section and a second sidewall section, for example shown in  FIGS. 18A-18C . 
     Referring to  FIGS. 6-8 , in the exemplary common suspended ceiling  24  application having a square-shaped air passage opening  26  and/or frame  28  shown in  FIG. 1 , exemplary housing  14  includes four modular sidewall sections  46  manufactured to be identical, or substantially the same (structural features and dimensions in the X  34 , Y  36  and Z  38  directions), including integral sidewall connectors discussed further below. In this example where the four sidewall sections  46  are the constructed or configured the same, the sidewall sections  46  are deemed to be modular in construction (i.e., each sidewall section  46  may be used in any of the four positions of the sidewalls  46  shown in  FIGS. 1 and 5-8  to define the interior cavity  68  to receive the filter media  18 ). Although examples of the air filter housing  14  are alternately described and illustrated as including two sidewall sections (two-piece design), or four sidewall sections  46  (best seen in  FIG. 6 ), it is understood that a fewer number, or greater number, of sidewall sections  46  may be used to suit the particular application. 
     In alternate examples (not shown), it is further understood that the individual sidewall sections  46  used to form housing  14  may not be modular (i.e., the sidewall sections  46  used to form housing  14  may include one or more alternately constructed sidewall sections  46  having different constructions, dimensions, features and/or orientations from other sidewall sections  46 ) to suit the particular application and performance specifications as known by those skilled in the art. In one example (not shown), where the forced air passage opening  26  or frame  28  is rectangular in dimensions, two of the four sidewall sections  46  will have a longer length than the two adjacent sidewall sections  46 . 
     Referring to the multi-piece housing  14  example including four modular sidewall sections  46  in  FIGS. 6-8 , as best seen in  FIG. 7 , exemplary sidewall section  46  includes a sidewall  50  having a lower end  54 , and an upper end  58  defining a sidewall height  56 . As best seen in  FIGS. 7 and 10A , sidewall  50  further includes a first end  60  having a corner portion  62 , and a second end  64  separated or positioned distant in the X  34  or Y  36  direction from the first end  60 , defining a sidewall length  66 . In one example, the sidewall length  66 , or alternately the length of the entire sidewall section  46 , is longer than the respective length or dimension of the air passage opening  26  ( FIG. 1 ) such that the connected sidewall sections  46  extend beyond, and circumferentially surround, a perimeter of the air passage opening  26  (e.g., the inner perimeter edge of the frame  28  defining the opening  26 ). In the example of the air passage opening  26  being an HVAC exhaust vent ( FIG. 1 ), this results in the housing  14 , and filter assembly  10 , capturing and/or maximizing the amount of forced-air, and the direction of the airflow  30 , through the interior cavity  68  of the housing  14  and the filter media  18 , for example filter cartridge  20 . 
     In one example, the sidewall section  44 ,  44 A,  46  is made of a polymer material, for example polyethylene, which may be molded and formed by common manufacturing processes, for example injection molding or vacuum forming, into a thin cross-section having good rigidity, stiffness, resilience, and impact resistance. Other polymers, elastomers, or composites, as well as light weight ferrous and non-ferrous metals, may be used to suit the particular application and performance requirements. 
     As best seen in  FIG. 1 , on connection of the sidewall sections  46 , the interior surfaces of the respective sidewalls  50  define an interior cavity  68  for receipt of the filter media  18  as further described below. In one example, the height  56  of the sidewall  50  is about four (4) inches in length to accommodate use with a common filter media cartridge  20  having a height or depth of 4 inches. The example sidewall height  56  of about 4 inches would alternately accommodate a common filter media cartridge  20  having a height or depth of two (2) inches. In an alternate example, the height  56  of the sidewall  50  is about 2 inches, for example to accommodate a common air filter cartridge  20  height or thickness of about 2 inches. Alternate sidewall heights  56  may be used, longer or shorter in length, to accommodate a wide variety of commercially available, high quality air filter media  18  heights, for example filter cartridges  20 , and/or to suit the particular application, for example desired air quality, or working space  32  environment. In an alternate example, in a suspended ceiling  24  application having a vent or louvered structure positioned in the opening  26  ( FIG. 1 ), the sidewall height  56  may be longer than 4 inches (or alternately 2 inches) to accommodate the desired thickness of the filter cartridge  20  as well as the depth or height of the vent structure inside the internal cavity  68  allowing the housing to connect flush with the frame  28  as further described below. 
     In one example, the length  66  of sidewall  50  is about 24 inches in length to accommodate a common size of 24 inches square for the air passage openings  26  used for commercial suspended ceilings  24 . It is understood that alternate dimensions for sidewall  50  length  66 , both larger or smaller (for example 48 inches or 12 inches), may be used to suit the particular application, environment, and/or performance requirements as understood by those skilled in the field. 
     As best seen in the  FIGS. 2, 3 and 12  example, sidewall section  46  includes an upper flange  70  connected to the upper end  58  of the sidewall  50 , and extends outwardly from the sidewall  50  and corner portion  62  along the X  34  or Y  36  directions as generally shown. In one example, upper flange  70  is substantially horizontally oriented and extends continuously along the upper end  58  of sidewall  50  and corner portion  62 . In one example, a length of the flange  70  (or horizontal portion thereof), is sized to be the same as, or slightly smaller, than a width of the frame  28  so the entire length of the flange  70  contacts or sits flush with the frame  28  between suspended ceiling panels supported by the frame  28 . It is understood that the upper flange  70  may take other sizes, dimensions, constructions, configurations, and/or orientations to suit the particular application. In alternate examples, the upper flange  70  may be directed inward toward internal cavity  68 , may not be continuous, or may not be included at all, to suit the particular application or environment as known by those skilled in the art. 
     In one example of housing  14  (not shown), a seal is connected to an upper surface  162  ( FIG. 17 ) of the upper flange  70 . The seal is operable to decrease or eliminate air flow  30  from passing between the frame  28  and the upper surface  162  of the upper flange  70 . In one example, the seal may be an adhesive-backed foam or elastomer material. Other seal devices, constructions, configurations, or materials may be used as known by those skilled in the art. 
     Exemplary air filter housing  14  further includes a filter media stop  74  that extends inward in the X  34  or Y  36  directions into the interior cavity  68 . The filter media stop  74  is operable to abuttingly or frictionally engage and provide a support surface for filter media  18 , for example filter cartridge  20 , in the housing  14  (i.e., to support and prevent the filter media  18  from passing or falling through the housing  14  along the Z-direction  38 ). 
     As best seen in the  FIGS. 6-8  example, one example of the filter media stop  74  is in the form of a lower flange  76  connected to, or positioned adjacent or in proximity to, the sidewall  50  lower end  54  as generally shown. The lower flange  76  extends inward toward the interior cavity  68  in the X  34  or Y  26  direction. In one example, lower flange  76  is integrally formed in the sidewall  50 , is oriented horizontally, or substantially horizontal (e.g., orthogonal to the sidewall  50 ), and extends continuously along the lower end  58  of sidewall  50 . 
     In the example best seen in  FIG. 5 , the lower flange  76  includes a distal end  77  positioned inward from the lower end  54  of the sidewall  50 . On connection of the sidewall sections  46  as shown in  FIG. 5 , the distal ends  77  form a housing air passage opening  77 A. As best seen in the  FIG. 5  example, the assembled air filter housing  14  housing air passage opening  77 A is unobstructed by the housing  14  (i.e., there are no cross-bars, vent grids, louvers, ribs, or other structures extending between the connected sidewall sections  46 , sidewalls  50 , the distal ends  77 , or lower flanges  76 , and/or spanning across or through the housing air passage opening  77 A. As best seen in  FIG. 4 , this unobstructed or clear housing air passage opening  77 A is advantageous in that substantially all of the filter media  18  lower surface facing the working space  32  ( FIG. 1 ) is easily visibly seen by working space  32  occupants who can readily see and/or inspect whether the air filter media is dirty and needs to be replaced. This is comforting and reassuring to working space  32  occupants that the air filter media  18  is in good or fresh working condition assuring the occupants of high or clean air quality. 
     Conventional air filter devices common use of grids, louvers, or other functional or aesthetic structures positioned in front of the filter media obstruct the view of the filter media which is often neglected, forgotten about, and not replaced for months or years compromising the effectiveness of the filter media and reducing air quality. The conventional devices&#39; use of grids or louvers also promotes the collection of dust, dirt and other particulates on the grids which can harbor germs, viruses, organisms, and other potentially hazardous substances which reduce air quality and are potentially harmful to working space  32  occupants. The conventional device use of grids or louvers further reduces the amount of air flow through the housing air passage opening  77 A, thereby reducing air circulation in the working space  32 . 
     In one alternate example (not shown), the lower flange  76  may include one or more separate flanges discontinuously spaced from one another along sidewall  50 . In one alternate example (not shown), each sidewall section  46  may include a single lower flange  76  extending along only a portion of the length  66  of sidewall  50 , for example positioned midway between the first end  60  and the second end  64  of the sidewall  50 . In an alternate example where the sidewall sections  46  are not all configured the same (e.g., two sidewall sections  46  are longer than the other two sidewall sections  46 ), only two of the four sidewall sections may include a filter media stop  74  or lower flange  76 . It is understood that the filter media stop  74 , and the example lower flange  76 , may take other dimensions, sizes, constructions, configurations, number of flanges, or orientations, to suit the particular application and performance specifications as known by those skilled in the art. 
     As best seen in the  FIGS. 1 and 4  example, on connection of the sidewall sections  46  to form housing  14  defining interior cavity  68 , the filter media  18 , for example the filter cartridge  20 , is axially inserted or installed in the interior cavity  68  in abutting engagement with the lower flange  76 . The lower flange  76  provides a supporting surface for the filter media  18  in the housing  14 . In one example generally described above, the sidewall sections  46  are sized or dimensioned such that the respective sidewalls  50  are positioned in close proximity to the exterior dimensions of the filter media  18 , for example the outer surfaces of the filter cartridge  20 , to minimize or prevent air flow  30  from passing between the sidewalls  50  and the filter cartridge  20  thereby avoiding passing through the filter cartridge  20  (i.e., the filtering media of the cartridge). In one example (not shown), a seal may be provided on the inside surface of the sidewalls  50  to contact or abuttingly engage the exterior side surfaces of the filter cartridge  20  positioned in the interior cavity  68  to further minimize or prevent air flow  30  from passing between the sidewalls  50  and the exterior sides of the filter media  18 . 
     In an alternate example (not shown) filter media stop  74  may include one structure, or a plurality of alternate structures, connected to the inside surface of the sidewalls  50 , to serve as a support surface or stop to support the filter media  18  when positioned in the internal cavity  68  of the housing  14 . In one example, the filter media stop  74  may include a single, or multiple, integrally formed protrusions, barbs and/or structural formations extending inward into the internal cavity  68  from the inside surface of two or more of the sidewalls  50 . In one example, triangular-shaped barbs or formations are integrally molded into the inside surface of sidewall  50  and extend inwardly into the interior cavity  68  to engage the filter cartridge  20  on installation into housing  14  and prevent movement of the filter cartridge  20  relative to the housing  14  while in use. The example triangular formations provide a flat surface for the filter cartridge  20  to engage and support the filter cartridge  20 . 
     In one alternate example, a flange or extension similar to lower flange  76  may be positioned above the sidewall lower end  54 , between the upper end  58  and the lower end  54 . The alternate example filter media stop  74  may be integrally molded into the sidewall  50 . The location and/or position of the filter media stop  74  along the height  56  of the sidewall  50  may be determined by the anticipated thickness or height (in the Z-direction  38 ) of the filter media  18  so that the entire height of the filter media  18  is positioned below the upper end  58  of the sidewall  50  or the upper flange  70  (as shown in  FIG. 3 ). Additional space between the top surface of the filter media  18  and the upper end  58  may be included to leave adequate space for a HVAC vent ( FIG. 1 ), for example. 
     Still referring to the  FIGS. 6-8  example, air filter housing  14 , and more particularly at least first sidewall section  44  and second sidewall section  44 A, each further include a sidewall connector  78  operable to connect the sidewall  50  first end  60  to an adjacent sidewall  50  second end  64 , and the sidewall  50  second end  64  to an adjacent sidewall  50  first end  60 , to form the air filter housing  14  defining the interior cavity  68  operable to receive filter media  18  as generally described above. In one example as best seen in  FIGS. 7 and 9-11 , the sidewall connector  78  includes a first sidewall connector  80  positioned at the sidewall  50  first end  60  and a complimentary second sidewall connector  86  positioned at the sidewall  50  second end  64  as generally shown. In one example, the first sidewall connector  80  and the second sidewall connector  86  are integral to the sidewall  50  (e.g., integrally formed or molded in a single piece or component). 
     As best seen in the  FIGS. 7, 9-10, 10A, and 10B  example, first sidewall connector  80  includes an elongate angled tab  90  which extends in the Z direction  38  as shown. In one example, angled tab  90  is an integral part of the sidewall  50  (i.e., formed as a single piece or component). As best seen in the  FIGS. 10, 10A and 10B  example, angled tab  90  includes a first portion  94  having a length  96  extending generally aligned or parallel to sidewall  50 , and having a width  98 . Angled tab  90  includes a second portion  100  connected to the first portion  94  having a length  102  extending substantially transversely (orthogonally 90 degrees) from the first portion  94  as generally shown, and including a width  104 . As best seen in  FIGS. 7, 10A, and 10B , angled tab  90  extends substantially the entire height  56  of the sidewall  50 . 
     As best seen for the angled tab  90  in the example in  FIGS. 7, 10, and 10B , the length  96  and the width  98  of the first portion  94  remain substantially constant in dimension as the angled tab  90  extends in the Z direction  38  from the lower end  54  of the sidewall  50  (e.g., adjacent to the lower flange  76 ) toward the upper end  58  of the sidewall  50  (e.g., adjacent the upper flange  70 ). In one example, the length  102  and the width  104  of the angled tab second portion  100  also increase as the angled tab  90  extends in the Z direction  38  from the lower end  54  of the sidewall  50  toward the upper end  58  of the sidewall  50 . Although described as the first portion  94  length  96  and width  98  dimensions remain substantially constant from the lower end  54  toward to upper end  58 , and the second portion length  102  and the width  104  increase in dimension as the angled tab  90  extends in the Z direction  38  from the lower end  54  toward the upper end  58  of the sidewall  50 , it is understood that each of the first portion length  96  and/or width  98 , and each of the second portion length  102  and/or width  104 , may vary in dimension other than as described. In other words, each of these lengths or widths may remain substantially constant, may increase, or may decrease along the angled tab  90  between the lower end  54  and the upper end  58  to suit the particular application and performance requirements. 
     As best seen in the  FIGS. 7-9, 11, 11A, and 12  example, exemplary second sidewall connector  86  includes an elongate angled channel  110  which extends in the Z direction  38  as generally shown. In one example, angled channel  110  is an integral part of the sidewall  50  (i.e., formed as a single piece or component). As best seen in  FIGS. 7, 11, 11A and 12 , exemplary angled channel  110  includes a length  112  and a width  113 . In the example, the length  112  increases as the angled channel  110  extends in the Z direction  38  from the lower end  54  of the sidewall  50  (e.g., adjacent the lower flange  76 ) toward the upper end  58  of the sidewall  50  (e.g., adjacent upper flange  70 ). In one example, the width  113  of the channel  110  remains substantially constant in dimension as the angled channel  110  extends in the Z direction  38  from the lower end  54  of the sidewall  50  toward the upper end  58  of sidewall  50  as generally shown. In an alternate example, it is understood that only one of the length  112  or the width  113 , for example length  112 , may increase as the angled channel extends in the Z direction  38  from the sidewall  50  lower end  54  toward the upper end  58 . 
     As best seen in the  FIGS. 8, 11, and 11A  example, the angled channel  110  defines an elongate angled slot  116  having a first portion  120  extending generally transverse (orthogonally 90 degrees) relative to sidewall  50  having a length  122  and a width  124 . In one example, the first portion  120  length  122  remains substantially constant in dimension as the angled slot  116  extends in the angled channel  110  in the Z direction  38  from the lower end (adjacent the lower flange  76 ) of the sidewall  50  toward the upper end  58  of the sidewall  50  (adjacent the upper flange  76 ). In one example the first portion width  124  of the angled slot  116  increases as the angled slot  116  extends in the angled channel  110  in the Z direction  38  from the lower end  54  of the sidewall  50  toward the upper end  58  of the sidewall  50 . 
     The example angled slot  116  further includes a second portion  126  in communication with the first portion  120  extending substantially transversely (orthogonally 90 degrees) from the first portion  120  as generally shown. The angled slot second portion  126  includes a length  128  and a width  130 . In one example of the angled slot  116 , the angled slot length  128  and the width  130  of the second portion  126  increase as the angled slot  116  extends in the angled channel  110  in the Z direction  38  from the lower end  54  of the sidewall  50  toward the upper end  58  of the sidewall  50 . Although described as the angled slot  116  first portion  120  length  122  remains of substantially constant dimension, and the first portion  120  width  124 , and the second portion  126  length  128  and width  130  increase as the angled slot  116  extends from the lower end  54  toward the upper end  58  of the sidewall  50 , it is understood that each of these dimensions may vary from as described. In other words, each of these lengths or widths may remain substantially constant, may increase, or may decrease along the angled slot  116  between the lower end  54  and the upper end  58  to suit the particular application and performance requirements. The tapered or angled geometries of the angled tab  90 , the angled channel  110 , and the angled slot  116  are functionally useful and advantageous for secure and removable connection of adjacent sidewall sections  46 , and further advantageous in the efficient and economical manufacture of the sidewall section  46  and housing  14  overall. 
     In an alternate example (not shown), the angled tab  90  and/or the angled channel  110  and defined slot  116 , may not be angled (i.e., the tab  90  and the channel  110  and defined slot  116  respective lengths and widths may be of constant, or substantially constant, dimension between the sidewall  50  lower end  54  and the upper end  58 ). In this example, the tab  90  lengths  96 ,  102 , and widths  98 ,  104  may be dimensioned to provide a sufficient interference or frictional fit with the channel  110  (having constant length and width dimensions) for a secure connection between the sidewall sections  46 . Alternately, another form or supplementary form of connection device as described herein may be used. It is understood that the angled tab  90 , angled channel  110  and angled slot  116  may be of different sizes, shapes, configurations and/or structures to suit the particular application and performance requirements as understood by those skilled in the field. 
     Referring to the  FIGS. 15 and 16  example, exemplary angled channel  110  is positioned or oriented at angles  142 ,  144  and  146  as generally shown. In one example, angles  142 ,  144  and  146  are 90.5 degrees as generally shown. Alternate angle value ranges for angles  142 ,  144  and/or  146  include 90-92 degrees (and any partial or fractional degree therebetween). Alternate angle values, both larger or smaller, for example 90-95 degrees (and any partial or fractional degree therebetween), for angles  142 ,  144  and/or  146  may be used to suit the particular application and environment. In one example, the above-described angles may also be used for first connector  80  elongate angled tab  90 . 
     In one example (not shown) the described respective increases in the lengths and widths of the angled tab  90 , the angled channel  110 , and the angled slot  116  as they extend from the sidewall  50  lower end  54  toward the upper end  58 , may be reversed (e.g., alternately, the angled tab  90 , the angled channel  110 , and the angled slot  116  lengths and widths may decrease from the lower end  54  toward the upper end  58  of the sidewalls  50 . In an alternate example (not shown), the angled tab  90  may be positioned at the sidewall  50  second end  64 , and the angled channel  110  may be positioned at the sidewall  50  first end  60 . 
     Referring to the example described and illustrated in  FIGS. 7-11 , in the first sidewall connector  80  in the form of the angled tab  90 , and the example second sidewall connector  86  in the form of the angled channel  110  and angled slot  116 , the angled tab  90  is sized to be complimentary to the angled slot  116 . In other words, the respective first portions  94  (angled tab),  120  (angled slot) and the respective second portions  100  (angled tab),  126  (angled slot) fit together in surrounding or coaxial orientation as shown in  FIG. 11  (angled tab  90  shown in dashed line). 
     As best seen in the  FIGS. 6 and 11  example, when adjacent sidewall sections  46  are to be connected, a sidewall section  46  is axially moved in the Z direction  38  to slidingly engage a first sidewall connector  80  (for example having an angled tab  90 ) of a sidewall section  46  to a second sidewall connector  86  (for example having an angled channel  110 ) of an adjacently positioned sidewall section  46 . As best seen in  FIG. 11 , the angled tab  90  is received in the angled slot  116 . In one example, the angled tab  90  and complimentary angled slot  116  are sized and/or dimensioned to provide a slight interference fit in one another over at least a portion of the tab  90  and angled channel  110  along the axial Z direction  38  for frictional engagement between angled tab  90  and the angled channel  110  providing for a secure, but removable connection between assembled adjacent sidewall sections  46  forming air filter housing  14  (space shown between angled tab  90  and angled channel  110  shown in  FIG. 11  for convenience of illustration only). As best seen in  FIG. 14 , connected adjacent sidewall sections form a joint  136 . In the example shown and described above, the abutting upper flanges  70  form a flush or substantially continuous and/or even surface, and the abutting lower flanges  76  form a flush or substantially continuous and/or even surface to support the filter media  18 , for example an air filter cartridge  20 . 
     In the example angled tab  90  and angled channel  110 , the described exemplary varying angled slot  116  and angled tab  90  lengths and widths are operable to begin the frictional engagement between the angled tab  90  and the angled channel  110  walls only when the angled tab  90  is engaged by the angled channel  110  walls defining slot  116  when the angled tab  90  is axially positioned about one-half of the way into the elongate slot  116  in the Z direction  38 . This example provides frictional engagement between the angled tab  90  and the channel  110  walls in about the last half of the insertion or installation stroke between the complimentary first sidewall connector  80  and the second sidewall  86  connector (e.g., frictional engagement or resistance first begins to occur when the angled tab  90  is about half of the way inserted or installed in the total length of the angled slot  116 ). Alternate examples may provide for the beginning of the frictional engagement at one-quarter of the insertion length along the Z direction  38 , or at three-quarters of the insertion length along the Z direction  38  (which would frictionally engage the adjoining sidewall sections  46  over only one quarter of the tab  90  and slot  116  length). Other examples of variations in sizes, shapes, forms, configurations, and orientations of the angled tab  90  and/or angled slot  116  (or angled channel  110  defining the angled slot  116 ), as well as the slight interference fit, and the frictional engagement by the first  80  and second  86  sidewall connectors, may be used to suit the particular application and performance requirements as known by those skilled in the art. 
     In one example, once the sidewall sections  46  are connected or assembled, the respective upper flanges  70  of the connected sidewall sections  46  are aligned, flush and/or are positioned in the same plane providing for an even, flat or planar surface along the top of housing  14  (e.g., at upper flange  70 ) to engage, for example, the air passage opening frame  28 . Similarly, once the adjacent sidewall sections  46  are connected, the respective lower flanges  76  are aligned, flush and/or are positioned in the same plane providing for an even, flat or planar surface along the bottom of the housing  14  (i.e., the inside surface of the lower flanges  76  facing the interior cavity  68  providing a support for the filter media  18 ). 
     In an alternate example (not shown) alternate structures or formations in the sidewall sections  46 , for example on tab  90  and/or channel  110  may be used to frictionally or otherwise engage adjacent sidewall sections  46  together. For example, one or more protrusions (e.g., a raised bump, dart or button) may be positioned on one of the tab  90  or channel  110  to engage an oppositely positioned and cooperative depression or hole in the other of the tab  90  or channel  110  to positively engage the sidewall section  46  together. Alternate structures and formations may be used as known by those skilled in the art. 
     Referring to the  FIG. 16  example, the position or angular orientation  140  of the sidewall  50  with respect to the upper flange  70  is 90.5 degrees (i.e., the sidewall  50  is oriented to be angled slightly outward from the vertical (for example Z direction  38 ) away from the interior cavity  68 ). This angle value is advantageous to eliminate or minimize the passage of air flow  30  between the housing  14  and filter cartridge  20  while maintaining use of efficient and economical manufacturing processes, for example injection molding or vacuum forming. Alternate angle value ranges for angle  140  include 90-92 degrees, 90-97 degrees, 90.5-92 degrees, or 90.5-97 degrees (and any specific angle or fractional angle within these ranges). In one example, angle  140  is 90 degrees. It is understood that different angles values for angles  140 ,  142 ,  144  and/or  146 , greater in value or lesser in value (and any factional angle therebetween), may be used to suit the particular application, to aid in manufacturing, and/or performance requirements as known by those skilled in the art. It is understood that the housing  14  configuration including the sidewall connector  78  in the form of the angled tab  90  and angled channel  110 , in the orientations and angles  140 ,  142 ,  144  and  146 , may be used with a housing  14  in the two-piece configuration, for example first sidewall section  44  and second sidewall section  44 A described herein. 
     Although air filter housing  14  is illustrated in  FIGS. 1-17  as including four (4) modular sidewall sections  46 , it is understood that the number and configuration of the sidewall sections  46  may vary. Referring to  FIGS. 18A-18E , schematic examples of alternate configurations of housing  14 , sidewall sections  46 , and sidewall connectors  78  are shown (spaces shown between the sidewall sections shown for convenience of illustration only, and the sidewall connectors shown schematically as lines). In one example where the air filter housing includes at least a first sidewall section  44  and a second sidewall section  44 A, it is contemplated that only two sidewall sections  46  may be used to form housing  14  which, when connected defines interior cavity  68 , and when installed, surrounds the forced air passage opening  26  as shown in  FIG. 1 . 
     Referring to the  FIGS. 18A, 18B and 18C  examples, alternately configured housing  14 A includes a first sidewall section and a second sidewall section similarly constructed and/or configured to the first sidewall section. In the  FIGS. 18A and 18B  examples, each of the first sidewall section  46 A and the second sidewall section  46 A are in the shape of a “C” or “U”. In the  FIG. 18A  example, the sidewall connector  78  may be in the form of the integral sidewall connector  78  described and best illustrated in  FIGS. 6-13 , or alternately may be any of the mechanical or chemical fasteners or methods described herein (e.g., screws, adhesive tapes, interlocking tabs, adhesives, and/or reclosable fastening devices and systems). Referring to the  FIG. 18A  example, the first and second sidewall sections  46 A are configured to overlap adjacent the respective ends which may be more suitable for the use of sidewall connector  78  in the form of mechanical or chemical fasteners described herein. 
     In the  FIG. 18B  example, the alternately configured housing  14 B first and second sidewall sections  46 A are oriented end-to-end and the sidewall connector  78 A is in an exemplary form of a separate and independent component, for example a flat or planar plate  82 . The plate  82  is connected to each of the sidewall sections  46 A by one or more mechanical or chemical fasteners described herein. 
     In the  FIG. 18C  example, the alternately configured housing  14 C first and second sidewall sections  46 B are in the form of a “J” shape. The first and second sidewall sections  46 B are connected by sidewall connector  78  in one of the many manners described for housing  14 A in  FIG. 18A  to suit the particular application. It is understood that the  FIGS. 18A-C  housing  14  examples using a two-piece sidewall section design, may have alternately configured sidewall sections  46  than described and illustrated to suit the particular application and performance requirements. 
     Referring to the  FIGS. 18D and 18  E examples, housing  14  is alternately configured using an alternate modular four-piece sidewall section  46  design. Referring to the  FIG. 18D  example, housing  14 D includes four sidewall sections  46 C which are configured as substantially straight or planar pieces of the same or similar construction (e.g., no corner portion  62  as shown in  FIG. 7 ). In the example, sidewall connector  78  is in the form of a separate and independent sidewall connector  78 B (not integral with the sidewall sections  46 ). In one example, alternate sidewall connector  78 B is in the form of an angled component or angle bracket  84  (four shown). In one example, the angle brackets  84  are connected to each of the adjacent sidewall sections  46 C through one or more of the mechanical or chemical fasteners described herein. 
     Referring to the  FIG. 18E  example, housing  14 E includes four modular sidewall sections  46 D, each configured in an “L” shape wherein portions of the sidewall sections overlap as generally described for  FIG. 18A . In one example, the sidewall connector  78  is in one of the forms as described for the housing  14  A in  FIG. 18A  (e.g., integral to sidewall section  46 D or one or more of the mechanical or chemical fasteners described). 
     Although the alternately configured housings  14 A- 14 E, and alternately configured sidewall sections  46 A- 46 D are illustrated schematically, it is understood that each of the variously described and illustrated sidewall sections  46 A- 46 D may include one or more of the sidewall section  46  constructions or features described above for sidewall section  46  and illustrated in  FIGS. 1-13 . For example, the alternately described sidewall sections  46 A- 46 D include the first and second ends, the upper and lower ends, and sidewall. The alternately described sidewall sections  46 A- 46 D may also include one or more of the variously described and illustrated filter media stop  74 , an upper flange  70 , a lower flange  76 , and/or housing connector  150 . Each of the alternate housings  14 A- 14 E when connected or assembled define an interior cavity  68  for receipt of the filter media  18  to form the air filter assembly  10  and are useful to connect to the air passage frame  28  to serve as an air filtration device as described and illustrated herein. 
     Referring to  FIGS. 3, 12, 14 and 17 , exemplary multi-piece air filter housing  14  includes a housing connector  150  operable to secure, connect, and/or engage the connected at least first sidewall section and second sidewall section (e.g., the air filter housing  14 ) circumferentially around the forced air passage opening  26 , for example to frame  28  ( FIG. 1 ). As described above, in one example, housing  14  includes four modular sidewall sections  46 . In the form of an air filter assembly  10 , the assembled housing  14  receives and supports an air filter media  18  prior to connection of the housing  14  to frame  28 . In the exemplary engaged position of the housing  14  to the air passage frame  28 , the housing completely, or substantially, circumferentially surrounds the air passage opening  26  and positions the air filter media  18  substantially transverse (orthogonally 90 degrees) to the airflow  30  as generally shown in  FIG. 1 . In a preferred example, housing connector  150  allows for secure, but removable connection or engagement of the housing  14 , or with air filter media  18  installed, air filter assembly  10 , to the air passage opening frame  28 . 
     As best seen in  FIGS. 2 and 3 , in one example application of housing  14  used in a commercial building suspended ceiling  24  frame  28 , the frame  28  is commonly made from a metallic or ferrous material including iron, for example light gauge steel. In this exemplary application, housing connector  150  includes at least one, or a plurality of, permanent magnets  152  (eight shown) spaced apart along upper flange  70  as generally shown. In the  FIGS. 2 and 3  example (showing use of a first, a second, a third, and a fourth sidewall section  46 ), each sidewall section  46  includes two round magnets recessed in the Z-direction  38  in the upper flange  70  as further described below. It is understood that different types of magnets, different numbers of magnets (in greater or lesser numbers), and different shapes or forms of magnets  152 , may be used to suit the particular application and performance specification as known by those skilled in the art. 
     As best seen in  FIGS. 12, 14 and 17 , the magnets  152  are spaced apart in the X  34  and Y  36  directions and mounted in recessed sockets  154  as generally shown. In one example, each recessed socket  154  is integrally formed in the sidewall section  46  upper flange  70  and sidewall  50  as best seen in  FIG. 17 . Each socket  154  includes an inner wall  158  and a bottom surface  160 . The sockets  154  are positioned and sized to receive the housing connector  150 , in the example shown an individual magnet  152 . In one example, each magnet  152  is permanently mounted in the recessed socket  154  with adhesive. Other devices and methods may be used to secure magnets  152  in the respective socket  154 . 
     In one example of housing connector  150  in the form of magnets  152 , each magnet  152  mounted in a recessed socket  154 , the bottom surface  160 , and/or height of the magnets  152 , are positioned or sized so that a top or upper surface of the magnets  152  is positioned adjacent to the sidewall upper end  58 . In one example, the magnet  152  upper surface is positioned substantially flush with an upper surface  162  of the upper flange  70 . This ensures that the upper flange  70  is placed in all-around abutting contact or engagement with the air passage frame  28  thereby eliminating or minimizing the passage of airflow  30  between the frame  28  and the housing  14 , avoiding passage through the filter media  18 . Alternately, the socket bottom surface  160  and/or the magnet  152  height are sized to position the upper surface of the magnet slightly below the upper surface  162  of the upper flange  70  to ensure the magnets  152  do not contact the air passage frame  28  prior to contact by the upper flange  70 . In an alternate example, the upper surface of the magnets  152  may be positioned to be slightly above the upper surface  162  of the flange  70  to ensure the magnets are in close proximity to the frame  28  to provide secure engagement of the housing  14  to the frame  28 . This position may also be beneficial if a seal (not shown) will be used between the flange  70  upper surface  162  and the frame  28 . 
     As best seen in the  FIG. 17  example, the housing connector  150  includes at least one tab  164  (two shown) which extend from the inner wall  158  inwardly into the recessed socket  154  and toward each other as generally shown. It has been determined that when mounting a magnet  152  in a recessed socket  154  with adhesive, the tabs  164  eliminate or reduce the occurrence of a vacuum air pocket forming between the magnet  152  and the bottom surface  160  and/or inner wall  158  which improves the permanent mounting of the magnets  152  to the sidewall section  46 . Other configurations, shapes, sizes, orientations and numbers of the tabs  164  may be used as known by those skilled in the art. 
     It is understood that different types of housing connectors  150  may be used to secure or removably connect the air filter housing  14  to the forced air device, for example, the HVAC forced air opening  26  or the frame  28 , or the housing of an electric circulation fan. It is understood that the numbers of housing connectors  150 , and/or the spacing and orientation of the housing connectors  150  relative to the housing  14 , may vary to suit the particular application. For example, housing connector  150  may alternately, or cooperatively, use interlocking or reclosable mechanical attachment devices, for example, hook and loop fasteners such as VELCRO®, Dual-Lock, adhesive tapes, and other similar devices which provide a secure, but low height or profile. The housing connector  150  may alternately, or cooperatively, use common mechanical fasteners such as screws, spring clips or clamps, or other known mechanical fastening devices. The described magnets  152  and alternate connectors may be connected to the upper flange  70 , or recessed in suitably sized and configured sockets or pockets as described for recessed sockets  154 . Other types of housing connectors  150  to suit the particular application or performance specifications known by those skilled in the art may be used. 
     It is further understood that different configurations of housing  14 ,  14 A-E, sidewall sections  46 ,  46 A-D (subsequently referred generally as sidewall  46  for convenience), and/or housing connectors  150  may be used to provide a secure, removable connection of the housing  14  (and air filter assembly  10 ) to the air passage opening frame  28 . In one example (not shown), the sidewall sections  46  may not include an upper flange  70  and the housing connectors  150 , for example magnets  152 , are connected to the sidewall  50  in an area, or adjacent to, the sidewall  50  upper end  58 . In another example (not shown), recessed sockets  154  may be eliminated and the housing connector  150 , for example magnets  152 , are mounted on the lower, or underside, of the upper flange  70  not in directly abutting contact with the air passage opening frame  28 . Other variations, configurations, formations, and components useful to removably connect housing  14  to air passage opening frame  28  allowing replacement of the filter media  18  from the housing  14  known by those skilled in the art may be used. 
     Although various examples of housings  14 , sidewall sections  46 , sidewall connectors  78 , and housing connectors  150  are described, it is understood that the variously described components and configurations may be interchanged with other of the described housing  14  components and configurations. For example, each of the various sidewall section  46  components, configurations, features and/or variations (e.g., sidewall  50 , first end  60 , second end second end  64 , corner portion  62 , and/or upper flange  70 ) may be used with any of the housing  14  configurations (e.g., housings  14 ,  14 A-E) described and/or illustrated herein. Equally, each of the variously described sidewall connectors  78  may be used with any of the housing  14  configurations described and/or illustrated herein. Also, the variously described filter media stops  74  (for example lower flange  76  or alternate protrusions as described) may be used with any of the housing  14  configurations described and/or illustrated herein. Equally, the variously described housing connectors  150  may be used with any of the housing  14  configurations described and/or illustrated herein. Also, the air filter assembly  10  including filter media  18  (for example filter cartridge  20 ) may be used with any of the various housing  14  configurations and variously described alternate components described and/or illustrated herein. 
     These singularly included, or combination, of structures and/or features to form the examples of housing  14  described and/or illustrated herein, each may include the variously described features and orientations of the angles  140 ,  142 ,  144  and/or  146 , and each may include the housing air passage opening  77 A which is unobstructed by the housing  14  providing the benefits and advantages as described herein. 
     Referring to  FIG. 19 , an example of a method  200  for assembling an air filter housing  14  is shown. Exemplary step  210  includes providing at least a first sidewall section  44  and a second sidewall section  44 A. In one example, the at least first sidewall section  44  and the second sidewall section  44 A include a total of four (4) modular sidewall sections  46 , a first sidewall section, a second sidewall section, a third sidewall section, and a fourth sidewall section  46  of the same, or substantially the same, dimensional, structural and functional features as described above and/or illustrated. 
     Step  215  includes aligning sidewall connectors  78  of adjacently-positioned sidewall segments  46 . In one example, each sidewall section  46  includes an integral first sidewall connector  80  positioned at a first end  60  of the sidewall  50 , and second sidewall connector  86  positioned at a second end  64  of the sidewall  50 . In one example the first sidewall connector  80  is the elongate angled tab  90 , and the second sidewall connector  86  is the elongate angled channel  110  defining angled slot  116  described above and/or illustrated. In alternate examples of sidewall connectors  78  described above, for example separate sidewall connectors, for example angle brackets, are used connect adjacently-positioned sidewalls  50 . These alternate, separate sidewall connectors are aligned or positioned with the respective sidewall  50 , or other structures of the sidewall sections  46 , and are operable to securely connect the adjacent sidewall sections  46  together to suit the particular configuration of sidewall  50 . 
     Step  220  includes connecting the at least first sidewall section  44  to the second sidewall section  44 A with the sidewall connector  78  forming a rigid, or semi-rigid, air filter housing  14  defining an internal cavity  68 . As describe above, in one example of housing  14 , four modular sidewall sections  46  are used. In one example, the first sidewall connector  80  is the integral angled tab  90 , and the second sidewall connector is the integral angled channel  110  defining an angled slot  116  as described above. The angled tab  90  is axially slidingly positioned in the angled slot  116  whereby the angled tab  90  is progressively frictionally engaged with the angled channel  110  to removably and securely connect the sidewall sections  46  together forming the assembled housing  14 . In the examples described and illustrated, the angled tab  90  of the first sidewall section  44  is aligned and received in the angled channel  110  angled slot  116  of the adjacently-positioned second sidewall section  44 A, and the angled tab  90  of the second sidewall section  44 A is aligned and axially received in the angled channel  110  and angled slot  116  of the adjacently-positioned first sidewall section  44 . In an alternate example, the at least first sidewall section  44  and the second sidewall section  44 A include four modular sidewall sections  46 , each of the four sidewall sections  46  angled tabs  90  and angled channels  110  are connected together to form the air filter housing  14  defining the internal cavity  68  as described above and/or illustrated. 
     In one optional step (not shown) a housing connector  150  is connected or attached to the at least first sidewall section  44  and the second sidewall section  44 A, for example each sidewall section  46  (e.g., where four modular sidewall sections  46  are used). In one example, the housing connector  150  includes at least one, or a plurality of, magnets  152  connected to the upper flange  70  of each sidewall section  46 . In another example described above, each magnet  152  is positioned in a recessed socket  154 . Alternate examples of housing connectors  150  and their operations are described above. When the sidewall sections are connected, the housing  14  is assembled and ready to receive a filter media  18  and be connected to a forced-air device, for example a HVAC system as shown and described for  FIG. 1 . 
     In an alternate step (not shown), when the housing  14  is not needed to filter the air and improve air quality in a working space  32 , the housing  14  can be disassembled and compactly stored through release of the sidewall connectors and disengagement of the sidewall sections  46  from each other. This is an advantage over conventional and/or one piece air filter designs which are large, bulky and take up considerable space when not in use and placed in storage. 
     Referring to  FIG. 20 , an example of a method  300  for assembling and installing an air filter assembly  10  to a forced air device, for example a HVAC forced air passage opening  26  defined by a suspended ceiling support grid frame  28 , or other air circulation device, for example an electric circulation fan frame, is shown. Exemplary step  310  includes assembling a multi-piece air filter air filter housing  14  having at least a first sidewall section  44  and a second sidewall section  44 A. In one example, four modular sidewall sections  46  are used and connected together as described above and/or illustrated. In one example, exemplary step  310  includes the method  200  for assembling the air filter housing  14  described and illustrated in  FIG. 18 . 
     In step  315 , a filter media  18  is installed in the assembled housing  14  interior cavity  68  in abutting engagement with the filter media stop  74  which supports the filter media  18  in the interior cavity  68  relative to the housing  14 . The assembled air filter housing  14  with the installed air filter media  18  forms the air filter assembly  10 . In one example, the filter media  18  includes a commercial air filter cartridge  20 . In one example, the filter media stop  74  is a lower flange  76  described above which supports the filter media  18  positioned in the internal cavity  68  as described above and/or illustrated. It is understood that the method step  315  may include the alternately described housing  14  configurations and alternate filter media stops  74  described herein. 
     Exemplary step  320  includes connecting or securing the assembled housing  14  and installed filter media  18  (as an air filter assembly  10 ) circumferentially surround a forced air passage opening  26 . In one example the forced air passage opening is defined by an air passage frame  28 . In one example, the frame  28  includes a suspended ceiling  24  support grid made from a metallic or ferrous material as described herein. In an alternate example, the frame  28  is a frame or housing of a forced air circulation device such as an electric circulation fan. In one example of step  320 , a housing connector  150  connected to the housing  14  is operable to connect the air filter assembly  10  to the frame  28 . Once connected to the frame  28  and circumferentially positioned around the air passage opening  26 , the connected air filter assembly  10  is operable to direct forced air  30  through the filter media  18  to either inside a working space  32 , or from a working space  32 . 
     In an optional step (not shown), on a need for replacement of the filter media  18  in the installed air filter assembly  10 , the housing  14  is disconnected from the frame  28  and from around the forced air passage opening  26 , the air filter media  18  is removed from the interior cavity  68 , and a new or refreshed air filter media  18  is installed in the housing  14  interior cavity  68  in engagement with the filter media stop  74  as describe and illustrated in the examples described herein. The air filter assembly  10  is then reconnected to the frame  28  circumferentially around the forced air passage opening  26  as described. 
     It is understood that additional method steps may be added, eliminated, and/or conducted in a different order than described for methods  200  and/or  300  to suit the particular application as known by those skilled in the art. 
     While the invention has been described in connection with certain embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.