Patent Publication Number: US-2019192721-A1

Title: Ultraviolet germicidal irradiation system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 15/184,150, flied Jun. 16, 2016; which is a continuation of U.S. application Ser. No. 14/538,471, filed Nov. 11, 2014, which is now U.S. Pat. No. 9,700,647; which is a continuation of U.S. application Ser. No. 13/742,035, filed Jan. 15, 2013, which is now U.S. Pat. No. 8,883,081; which is a continuation of U.S. application Ser. No. 13/229,293, flied Sep. 9, 2011, which is now U.S. Pat. No. 8,354,060, Issued Jan. 15, 2013; which is a continuation of U.S. patent application Ser. No. 10/932,997, filed Sep. 2, 2004, which is now U.S. Pat. No. 8,038,949, issued Oct. 11, 2011. The disclosure of each of the above-referenced applications is hereby incorporated herein by reference in its entirety. 
     The present invention relates generally to an ultraviolet germicidal irradiation system for sterilization of microorganisms in various applications. More specifically, the present invention relates to an ultraviolet germicidal irradiation system for use in residential, commercial, and industrial heating, ventilation, and air-conditioning (“HVAC”) applications. 
    
    
     BACKGROUND OF THE INVENTION 
     Contaminated air in buildings and homes is now an international issue. Certain airborne contaminants cause widespread discomfort and health problems, leading to absenteeism from school and work, as well as reduced productivity. Healthy and productive indoor environments would save billions of dollars in health care costs, lost work time, overall output and possible litigation. 
     Of the many contaminants found in indoor air, bioaerosols are regarded as the leading cause of allergies and other maladies referred to as SBS (Sick Building Syndrome) and BRI (Building-Related Illness). Bioaerosols are airborne products that include microorganisms, their fragments and spores, metabolic gases, and other toxins and waste products. Numerous studies have found high concentrations of these bioaerosols both in air handling equipment and the interiors they serve. 
     Airborne and surface microorganisms include pathogens, allergens, and toxins. Included in the category of pathogens are viruses, bacteria, and mold, which could cause measles, chicken pox, Legionnaires disease, aspergillosis, tuberculosis, and other infectious disease. Bacteria and mold are also classified as allergens because they can cause allergic rhinitis, asthma, humidifier fever and hypersensitivity pneumonitis. Toxins include mycotoxins and endotoxins, which can cause toxic and allergic reactions, irritations, and odors. Among allergens, mold and mold products are probably the most common worldwide. 
     Allergy tests universally bear out this phenomenon. In HVAC equipment, mold can proliferate year-round. With most individuals, prolonged exposure to mold and mold products initiates the release of histamines, causing inflammation of mucous membranes, which can be followed by congestion, breathing difficulties, asthma and other respiratory complications. 
     Conventional HVAC systems are an ideal source and conduit for the origin and/or spread of microorganisms. Their environments are especially conducive to amplifying molds and some bacteria. The fans of the HVAC system disseminate and/or recirculate system, space and occupant-generated microorganisms room to room and person to person. Conventional filtration assemblies of such HVAC systems are compromised because growth typically occurs downstream of filters, which allows microorganisms to seed in the ductwork and travel to and throughout the occupied space. Additionally, viruses and many bacteria are too small to be captured by a common air filter. 
     Traditional bioaerosol controls tend to be impractical, toxic, detrimental to equipment operation, and costly. Hence, the industry has turned to ultraviolet germicidal irradiation (“UVGI”) for the sterilization of microorganisms. In HVAC systems, the application of UVGI in the air handling unit cooling coil and filter assemblies is effective in reducing the number of microorganisms. Additionally, the constant irradiation exposure has been found to be effective at controlling fungal growth. 
     Microbes are uniquely vulnerable to the effects of light at wavelengths at or near 2537 Angstroms, due to the resonance of this wavelength with molecular structures. A quantum of energy of ultraviolet light at these wavelengths possesses an amount of energy sufficient to break organic molecular bonds, which damages the cellular structure of the microorganisms. 
     The ultraviolet component of sunlight is the main reason microbes die in the outdoor air. The die off rate in the outdoors varies from one pathogen to another, but can be anywhere from a few seconds to a few minutes in order to kill 90 to 99% of viruses and contagious bacteria. Spores and some environmental bacteria tend to be resistant and can survive much longer exposures. UVGI systems use much more concentrated levels of ultraviolet energy than are found in sunlight. 
     The kill rate of pathogens and other microorganisms using UVGI depends on several factors, including UVGI intensity, the number of microorganisms present, and the amount of time the microorganisms are present in the UVGI zone, or dwell time. Generally, kill rate increases as the UVGI intensity is increased and/or the dwell time is increased. 
     SUMMARY 
     The invention described herein is a germicidal light grid system. In one example, the light grid system is positioned inside a plenum. The light grid system can be positioned adjacent to a cooling apparatus, such as, for example, an evaporative cooling coil. One can appreciate that such a light grid system is not limited for use inside a plenum, nor is it limited when used inside of a plenum to being positioned adjacent to cooling apparatuses. For instance, the light grid system can be used in plenums adjacent to air filtration banks, air intake vents, air mixing junctions, and/or plenum transition areas. 
     The light grid system of the present invention comprises at least one elongate member, at least one lamp assembly, and at least one germicidal light source. The at least one elongate member is mounted within a plenum in which a stream of air is entrained therein. In one aspect, the at least one elongate member can be connected to a portion of the plenum. 
     In one example of the light grid system, the at least one lamp assembly is mounted at a predetermined position on a portion of one of the elongate members. The predetermined position is operator selectable and can include any portion of the elongate length of the elongate member. Each lamp assembly comprises a housing defining at least one socket that extends at an acute angle relative to a transverse axis of the housing. The linear light source has a longitudinal axis and a distal end that is constructed and arranged to releasably mount within one socket of the housing. In use, each light source extends therein the stream of air such that the longitudinal axis of the light source is positioned at an acute light angle relative to the direction of flow of the stream of air. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features of the preferred embodiments of the present invention will become more apparent in the detailed description in which reference is made to the appended drawings wherein: 
         FIG. 1  is a top elevational view of one embodiment of the germicidal irradiation system of the present invention mounted therein a plenum. 
         FIG. 2  is a front elevational view of the germicidal irradiation system of  FIG. 1 . 
         FIG. 3  is a side elevational view of the germicidal irradiation system of  FIG. 1 . 
         FIG. 4  is a perspective view of a portion of an exemplified elongate member of a support assembly of the present invention. 
         FIG. 5  is a cross-sectional view of the elongate member of  FIG. 4  taken across section 5-5. 
         FIG. 6  is a top elevational view of one embodiment of a lamp assembly of the germicidal irradiation system of the present invention spaced from a cross-sectional view of an exemplified elongate member, and showing a housing, at least one linear light source mounted therein sockets of the housing, the linear light source being angled at an acute angle α with respect to the transverse axis of the housing. 
         FIG. 7  is a front elevational view of the lamp assembly of  FIG. 6  showing a ballast device disposed therein an internal cavity of the housing. 
         FIG. 8  is a side elevational view of the lamp assembly of  FIG. 6 , showing a flange member adapted to mount within a portion of an exemplified elongate member. 
         FIG. 9  is a top elevational view of an alternative embodiment of a lamp assembly of the germicidal irradiation system of the present invention spaced from a cross-sectional view of an exemplified elongate member, and showing a housing, at least one linear light source mounted therein sockets of the housing, the linear light source being angled at an acute angle α with respect to the transverse axis of the housing. 
         FIG. 10  is a front elevational view of the lamp assembly of  FIG. 9  showing a ballast device disposed therein an internal cavity of the housing. 
         FIG. 11  is a side elevational view of the lamp assembly of  FIG. 9 , showing a flange member adapted to mount within a portion of an exemplified elongate member. 
         FIG. 12  is a top elevational view of an alternative embodiment of a lamp assembly of the germicidal irradiation system of the present invention spaced from a cross-sectional view of an exemplified elongate member, and showing a housing, a linear light source mounted therein a socket of the housing, the linear light source being angled at an acute angle α with respect to the transverse axis of the housing. 
         FIG. 13  is a side elevational view of the lamp assembly of  FIG. 12 , showing a flange member adapted to mount within a portion of an exemplified elongate member. 
         FIG. 14  is a front elevational view of the lamp assembly of  FIG. 12  showing a ballast device disposed therein an internal cavity of the housing. 
         FIGS. 15-20  are top, front, and side elevational views of exemplary constructions of the germicidal irradiation system of the present invention showing the linear light source being positioned an the acute angle α with respect to the transverse axis of the housing and showing the lamp assembly being mounted to the elongate member such that the longitudinal axis of the light source extends therein the stream of air at an acute light angle relative to the direction of the flow of the stream of air entrained in the plenum. In one aspect, the longitudinal axis of the light source is positioned at an acute light angle θ relative to the common plane formed by a first elongate member and a second elongate member of a support assembly. In one aspect, the common plane formed by the first and second elongate members is substantially transverse to the direction of the flow of the stream of air. 
         FIG. 21  are perspective views of an exemplary fastener and planar member for connecting the housing of the light assembly to an elongate member. 
         FIG. 22  is a perspective view of one embodiment of a mount for connecting a first elongate member of the support assembly to a portion of a second elongate member of the support assembly. 
         FIG. 23  is a perspective view of a flange member of a housing of the light assembly of the present invention. 
         FIG. 24  is a top elevational view of an alternative embodiment of a lamp assembly of the germicidal irradiation system of the present invention spaced from a cross-sectional view of an exemplified elongate member, and showing a first body, a second body, and an elongate conduit extending therebetween, and showing a linear light source mounted therein a socket of the second body of the housing, the linear light source being angled at an acute angle α with respect to the transverse axis of the housing. 
         FIG. 25  is a side elevational view of the lamp assembly of  FIG. 24 , showing a flange member adapted to mount within a portion of an exemplified elongate member. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is more particularly described in the following exemplary embodiments that are intended as illustrative only since numerous modifications and variations therein will be apparent to those skilled in the art. As used herein, “a,” “an,” or “the” can mean one or more, depending upon the context in which it is used. The preferred embodiments are now described with reference to the figures, in which like reference characters indicate like parts throughout the several views. 
     Ranges may be expressed herein as from “about” one particular value, and/or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment. 
       FIGS. 1-3  illustrate one embodiment of a modular germicidal light grid system  10 . This embodiment of the light grid system is designed for use inside a plenum  2  in which a stream of air  4  is entrained and flows in a predetermined direction. The light grid system  10  can be positioned adjacent to a cooling apparatus  6 , such as, for example, an evaporative cooling coil. One can appreciate that the light grid system  10  of the present invention is not limited for use inside a plenum, nor is it limited when used inside of a plenum to being positioned adjacent to cooling apparatuses. For instance, the light grid system  10  of the present invention can be used in plenums  2  adjacent to air filtration banks, air intake vents, air mixing junctions, and/or any plenum transition area. 
     In one aspect, the light grid system  10  comprises at least one elongate member  20 , at least one lamp assembly  50 , and at least one linear germicidal light source  70 . The elongate member  20  is positioned within the plenum  2 . Each lamp assembly  50  comprises a housing  52  having a transverse axis, as is shown in  FIGS. 6-14 . In one example of the light grid system  10 , the transverse axis of the housing  52  is substantially perpendicular to a plane transverse to the direction of flow of the stream of air  4 . However, the transverse axis of the housing  52  can be positioned in any desired relation to the direction of flow of the stream of air  4 . The housing  52  defines at least one socket  54  that extends at an acute angle α relative to the transverse axis of the housing. A portion of the housing  52  of each lamp assembly is constructed and arranged to mount to a portion of the at least one elongate member  20  at a predetermined position that is operator selected. The predetermined position can, as one will appreciate, be any portion of the elongate length of the elongate member, as desired. 
     Each linear light source  70  has a longitudinal axis and a distal end  72  constructed and arranged to mount within one socket  54  of the housing. As one will appreciate, it is contemplated that the light source can be removeably replaced as maintenance requires. In one aspect, the at least one lamp assembly  50  is mounted to the at least one elongate light member  20  such that the longitudinal axis of the at least one light source  70  extends therein the stream of air and is positioned at an acute light angle relative to the direction of the flow of the stream of air  4 . 
     In one aspect, the at least one elongate member forms  20  a part of a modular support assembly  22 . In use, the modular support assembly  22  of the present invention provides for the economical and efficient construction of a support structure that can be dimensioned as desired to fit within the particular physical dimensions of the plenum  2 . Prior germicidal light systems required a “custom fit” preparation of a support structure that increased the expense of the installed air treatment system and the lead time required for installation (for the actual physical construction of a “custom” structure). 
     In one example, the modular support assembly  22  of the present invention comprises at least one elongate first member  24  and at least one elongate second member  26  positioned substantially perpendicular to the elongate first member. One or more of the elongate first or second members  24 ,  26  can be connected to a portion of the plenum  2 . In one aspect, the at least one elongate first member  24  and the at least one elongate second member  26  are positioned within a common plane. In one aspect, the housing  52  of the light assembly  50  can be mounted to the elongate member  24 ,  26  such that the transverse axis of the housing  52  is substantially perpendicular to the common plane of the elongate first and second members. 
     In one embodiment, the elongate second member  26  can be constructed from 1⅝″ three walled strut type channel UL electrical raceway material. As one will appreciate, the elongate first member  24  can also be constructed from the same material. Using conventional raceways that can be mounted to each other with conventional fasteners and/or mounts allows for expedient construction of the support assembly. As one will appreciate, these are merely representative examples of construction materials and methodologies. For example, the elongate first and second members  24 ,  26  can be connected in any of a number of ways, such as, for example, with conventional fasteners. 
     In one aspect, the at least one linear germicidal light source  70  extends such that the longitudinal axis of the light source is positioned at an acute light angle θ, relative to the common plane formed by the first and second elongate members  24 ,  26 . In one aspect, the common plane formed by the first and second elongate members  24 ,  26  is substantially transverse to the direction of flow of the stream of air  4 . The linear light sources  70  can be, for example, 22″ double arc length 4-pin germicidal lamps, such as the TUV PL-L 55W/HF made by Philips™. However, as one skilled in the art will appreciate, any elongate ultraviolet germicidal lamp can be used. 
     In one example of the system, the preferred acute light angle θ is about 10° to less than about 90°. More preferably, the acute light angle θ is between about 20° to about 80°. Even more preferred, the acute light angle θ is between about 30° to about 70°. Still more preferred, the acute light angle θ is about 30°, or alternatively, about 45°. 
     In one example, at least one elongate first member  24  is spaced at predetermined distance from the cooling apparatus  6 . In another aspect, at least one elongate second member  26  can be positioned at the same predetermined distance from the cooling apparatus  6 , or, alternatively, can be at a different predetermined distance. In one example of the light grid system, the predetermined distance is preferably between about 3″ and about 24″. More preferably, the predetermined distance is between about 5″ and about 20″. Still more preferred, the predetermined distance is about 18″. Alternatively, the predetermined distance is about 12″. In still another alternative aspect, the predetermined distance is about 6″. 
     As is depicted in  FIG. 1 , in one example of the light grid system  10  each socket  54  of the housing  52  has a longitudinal axis that is oriented rearwardly away from the cooling apparatus  6 . In yet another example, each socket  54  of the housing  52  has a longitudinal axis that is oriented forwardly toward the cooling apparatus  6 . In still another example, the light grid system  10  has at least one socket  54  oriented rearwardly away from the cooling apparatus  6  and at least one socket  54  oriented forwardly toward the cooling apparatus  6 . 
     As shown in  FIGS. 10-13 , in one embodiment, the light grid system  10  of the present invention further comprises a power supply  80  and at least one ballast device  82  electrically coupled to the power supply and the at least one socket  54  of the housing. In one aspect, the housing of each light assembly can define an internal cavity  56  that is sized and shaped for the at least one ballast device  82  to be disposed therein. In another example, the ballast device  82  is located at a remote location spaced from the housing. The ballast device  82  can be electrically coupled to the power supply  80  conventionally, for example, by using conventional  3  or  6  stranded electrical wires. 
     One example of the ballast device  82  is a solid-state, non-potable, high frequency ballast operating at about either 120 or 277 volts AC and at about 50 to 60 Hz. For exemplary lamp assemblies  50  with two germicidal light sources, a single uniform ballast allows for subsequent simplicity for inventory and change requirements by the end user. In one aspect of the ballast device  82 , the ballast device is self-regulating with direct current output. In one aspect, the ballast device  82  for the exemplary two light source lamp assembly  50  can deliver up to about 110 watts to each lamp or about 220 watts total. In one aspect, the ballast device  82  for an exemplary one light source lamp assembly  50  can deliver up to about 140 watts to the lamp. 
     In practice, the housing that contains the ballast device  82  can be pre-wired for connection to the remote power supply  80 . In this example, the ballast device  82  can include a wiring assembly  84  that extends from the internal cavity  56  of the housing through a port  58  defined in the housing  52 . In this example, the support assembly  22  and the at least one lamp assembly  50  mounted thereto, can be constructed completely by the installer. Then, after the construction is complete, an electrician can electrically connect the wiring assembly  84  extending from the mounted lamp assemblies  50  to the power supply by coupling the wiring assembly  84  to the electrical wire  81  that extends to the power supply  80 . 
       FIGS. 6, 9 and 14  show an example of the lamp assembly in which the lamp assembly  70  is releasably mounted to the elongate member, for example, a second elongate member  26 , of the support assembly. As one will appreciate, having the lamp assembly  70  releasably attached to the elongate member  20  provides for convenient installation and disassembly. However, it will be appreciated that any number of attachment techniques including providing permanent attachments are contemplated. 
       FIGS. 4 and 5  illustrate an example of the support assembly  22  in which the elongate second member  26  and/or the elongate first member  24  defines a trough  30 . Further, a portion of the housing  52  is sized and shaped for disposition within a portion of the trough  30  of the elongate member  20 . In one example, the elongate second member  26  can have a substantially U-shape in cross-section. As one skilled in the art will note, the elongate member  20  can have any number of varied cross-sectional shapes, including, for example, a V-shape, a C-shape, and the like. In one aspect, a portion of the housing  52  is adapted for a friction fit within the portion of the trough  30  of the elongate member  20 . 
     In this embodiment, the trough  30  acts as a conduit that is adapted for disposition of wiring that couples the power supply  80  to the ballast device  82  and subsequently to the at least one socket  54  of the housing. Additionally, as exemplified in  FIG. 23 , a closure strip  29  can be provided to seal the open portion of the trough  30  after wiring of the light grid system  10  is complete to seal the inside of the trough from the ambient environment. Thus, the formed conduit acts as an electrical raceway that enables the system assembler to conceal any necessary electrical wires. 
       FIGS. 4 and 5  also show an example wherein the elongate second member  26  defines a trough  30  that has a pair of opposing, longitudinally extending, edges  32  that bend inwardly to form a pair of opposing male protrusions  34 . A portion of the housing  52  is sized and shaped for disposition within a portion of the trough  30 . In one aspect, the portion of the housing  52  defines an elongate flange member  60  having a pair of longitudinally extending, opposing male protrusions  62 . The opposing male protrusions  62  of the flange member  60  are sized and shaped for overlying registration within the portion of the trough  30  of the elongate second member  26 . As one will appreciate, the pair of opposing male protrusions  62  of the flange member  60  can be adapted for a friction fit with the portion of the trough  30 . 
     In one aspect, and as exemplified in the figures, the housing  52  is positioned on an elongate second member  26  using a snap-fit connection. This configuration allows the independent installation of the support assembly and lamp assembly to be constructed by non-electrically qualified personnel such as mechanical contractors. Once the support assembly  22  is constructed and the lamp assemblies  50  are mounted thereon, a second independent installation of the electrical components can be completed by qualified electrical contractors. Additionally, the snap in feature used in this example allows the electrical contractor to wire the lamp assembly without dismantling the housing  52 . It also enables the end user to quickly remove and replace the lamp assembly. 
     Another example of the light grid system  10  is shown in  FIGS. 4, 5 and 21 . Here, the pair of opposing male protrusions  34  of the trough  30  are spaced apart a predetermined distance. This predetermined distance, for example, preferably can be between about ½″ and 2″. More preferably, the predetermined distance is about ⅞″. In this example, the second elongate member  26  further comprises a fastener  35  coupled to the housing  52  of the light assembly and a planar member  36  that defines a bore  37 . The planar member  36  in this example has a dimension greater than the predetermined distance and is sized and shaped for positioning within a portion of the trough  30 . In this example, the fastener  35  and the bore  37  are complementarily sized and shaped so that, in use, the fastener engages the bore of the planar member to force a portion of the planar member into contact with a portion of the pair of opposing male protrusions  34 . This acts to secure the housing  52  of the light assembly  50  in the predetermined position on the elongate member. 
       FIG. 22  illustrates one embodiment of a light grid system  10  in which the elongate second member  26  is slidably mounted to the elongate first member  24 . This allows for rapid adjustment of the elongate second member with respect to the elongate first member should it be needed. It is contemplated that the second elongate member can be releasably fixed to the first elongate member when the respective elongate members are at their desired positions. 
     In an alternative embodiment of the lamp assembly  50 , as shown in  FIGS. 24 and 25 , the housing  52  of the lamp assembly comprises a first body member  51 , an opposed second body member  53 , and an extension conduit  55  connected to and extending there between the first and second body members. In one aspect of this embodiment, the extension conduit extends substantially coaxial to the transverse axis of the housing. The at least one socket  54  is defined on the second body member  53 . A portion of the first body member  51  of the housing  52  is constructed and arranged to mount to the portion of the elongate member as described above. In a further aspect, the first body defines the mutual cavity  56  sized and sloped for the at least one ballast device  82  to be disposed therein. 
     As noted above, the light grid system  10  of the present invention is constructed to be positioned inside of a plenum  2  in which a stream of air  4  is entrained. The stream of air has a direction of flow, in which contaminants and pathogens may exist. Positioning the light sources  70  at an acute light angle, θ, relative to the common plane formed by the two elongate members, wherein the plane is perpendicular to direction of flow, increases the distance the contaminants and or pathogens must travel inside of the UVGI zone. Thus, the microbial dwell time inside the UVGI zone is increased, providing for a higher kill rate of pathogens or contaminants as compared to a system in which θ is 0° or 90°. 
     In another aspect, the angle at which the lamps are positioned is determined by the acute angle α, at which the socket extends relative to the transverse axis of the housing. In one preferred example of the light grid system, the acute angle α, is about 10° to less than about 90°. More preferably, acute angle α is between about 20° to about 80°. Even more preferred, acute angle α is between about 30° to about 70°. Still more preferably, acute angle α is about 45°, or alternatively, is about 60°. 
     Also disclosed is a performance standard for the measuring UVGI in a germicidal light grid system. These UVGI factors are calculated using the Inverse Square Law, which can be written 
     
       
         
           
             
               I 
               = 
               
                 S 
                 
                   4 
                    
                   
                       
                   
                    
                   π 
                    
                   
                       
                   
                    
                   
                     r 
                     2 
                   
                 
               
             
             , 
           
         
       
     
     wherein I is the intensity of the influence, S is the source strength and r is the distance from the source. For convenience, four levels of performance capability are disclosed. They are as follows:
         Level 1: Minimum UVGI factor of 9.   Level 2: Minimum UVGI factor of 16.   Level 3: Minimum UVGI factor of 36.   Level 4: Minimum UVGI factor of 144.       

     The primary function of a system at Level 1 is the surface disinfection of stationary devices. The secondary function of Level 1 is for the deactivation of microbial agents in dynamic motion within a moving airstream. For the purpose of ease of discussion, in this and all of the following discussions regarding performance capabilities, we assume that there are two germicidal light sources  70  per lamp assembly  50  and that the light sources used are the aforementioned Philips™ germicidal lamps. As such, in one example, the spacing of the germicidal light sources  70  along the elongate second member  26  is about 48″ in order to maintain a UVGI factor of 9. Exemplary spacing between germicidal light sources  70  on separate elongate second members  26  is about 24″ in order to maintain a UVGI factor of 9. 
     The primary function of Level 2 capability is for the deactivation of microbial agents in dynamic motion within a moving airstream. The secondary function of Level 2 is for the disinfection of stationary sources, typically air-handling system components. In one example, vertical spacing of the germicidal light sources along the elongate second member is about 36″ in order to maintain a UVGI factor of 16. Exemplary spacing between germicidal light sources on separate elongate second members is about 18″ in order to maintain a UVGI factor of 16. 
     The primary function of Level 3 capability is for the deactivation of microbial and pathogenic agents in dynamic motion within a moving airstream. The secondary function of Level 3 is for surface disinfection of stationary devices, typically mission critical process filtration air-handling system components. For example, vertical spacing of the germicidal light sources along the elongate second member is about 24″ in order to maintain a UVGI factor of 36. Exemplary spacing between germicidal light sources on separate elongate second members is about 12″ in order to maintain a UVGI factor of 36. 
     The primary function of Level 4 capability is for the deactivation of microbial and pathogenic agents in dynamic motion within an airstream. The secondary function of Level 4 is for surface disinfection of stationary devices, typically mission critical process filtration air-handling system components. In one example, vertical spacing of the germicidal light sources along the elongate second member is about 12″ in order to maintain a UVGI factor of 144. Here, the germicidal lamps on separate elongate second members are crossed, with an example being between them of about 6″ in order to maintain a UVGI factor of 144. 
     Although several embodiments of the invention have been disclosed in the foregoing specification, it is understood by those skilled in the art that many modifications and other embodiments of the invention will come to mind to which the invention pertains, having the benefit of the teaching presented in the foregoing description and associated drawings. It is thus understood that the invention is not limited to the specific embodiments disclosed hereinabove, and that many modifications and other embodiments are intended to be included within the scope of the appended claims. Moreover, although specific terms are employed herein, as well as in the claims which follow, they are used only in a generic and descriptive sense, and not for the purposes of limiting the described invention, nor the claims which follow.