Abstract:
A fan filter unit for clean rooms has baffle structures sized and placed to limit the paths of entry of air flow from the unit motorized fan to the outlet ports, the baffle structures extending for a vertical height sufficient to avoid reversal of air flow within the enclosure for lower energy requirements in the unit while controlling noise levels and keeping BTU output low.

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Applications Ser. No. 60/097,695 filed Aug. 24, 1998, and Ser. No. 60/130,091 filed Apr. 20, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to fan filter units useful in clean rooms and like applications. More particularly, the invention relates to a fan filter unit that simultaneously achieves all the major objectives for such a unit: 
     1. Filtration efficiency of 99.999% at 0.12 micron particles, at 
     2. Air flows of about 90 FPM, 
     3. Energy usage of about 100 watts, and 
     4. Lower BTU output for reduced air conditioning load. 
     Fan filter units typically are suspended individually or in banks above a workspace, each individual fan filter unit combines a motorized fan, a fan enclosure supporting the fan, and filter media in a filter unit downstream from the fan enclosure all arranged to introduce, e.g. HEPA or ULPA filter-processed air into the workspace environment. The invention advantageously uses a filter pack of relatively increased depth, e.g. 5 inches of depth and greater, no metal separators, and increased pleat count, e.g. 5 to 7 pleats per inch, for maximum energy efficiency. Prior art fan filter units use more energy, are less efficient, and comprise, typically, less deep packs, e.g. 2-4 inches in depth. 
     2. Related Art 
     Known filter fan units are desirably improved in terms of filtration efficiency, quietness of operation and energy efficiency including both energy consumed directly by the filter units to drive the fans and energy consumed indirectly by the units through heat output into the air-conditioned room. Achieving the one should not detract from achieving the other. Presently popular fan filter units use trough-like transverse baffles to redirect the air flow from a first direction, generally radially outward from the fan, to a second, opposite direction, generally toward the fan and within the height of the filter fan unit enclosure, see generally U.S. Pat. No. 5,470,363 to Leader et al. Reversing flow will usually entail excess energy consumption and prevent achieving of the desired low energy consumption of about 100 watts or less. 
     SUMMARY OF THE INVENTION 
     The present invention uses linear, unidirectional flow of pressurized air from a motorized fan through perimetrically distributed outlet ports. The occurrence of backflows and the backpressure development common in reverse flow devices like that shown in U.S. Pat. No. 5,470,363 and the concomitant unnecessarily high energy consumption is avoided in the invention. Linear, unidirectional flow of pressurized air in the present invention derives from use of baffle structures in advance of the outlet ports, not within the ports, and the use of baffle structures that direct all air flow linearly through the fan enclosure outlet ports. Linear air flow is obtained by extending the baffle structures vertically from about 25% of the enclosure height to the full enclosure height, i.e. from the bottom wall to top wall of the enclosure, giving them a wedge shape that is conducive to smooth air flow, and extending them laterally for at least substantially the width of the outlet ports along their respective side walls. Thus avoided is a reverse flow of air within the height of the filter fan unit enclosure and within the port. Baffle structures extending at least about 25% of the enclosure height limit air flow to lateral (from the side) flows and “waterfall” flows over the baffle structure into the port, all linear flows, while baffles the full height of the enclosure limit air flow to paths extending laterally about the baffle structures. Both types of flow ensure the absence of reverse air flow within the fan surrounding enclosure. The baffles are suitably covered with sound-absorbing material such as foam and, with the walls of the enclosure, define a non-straight air flow path to control and absorb any noise generated within the enclosure. Typical of the prior art is the fan filter unit shown in the above-mentioned U.S. Pat. No. 5,470,363. There the fan filter unit has an integrated fan filter unit and filter. The pressurized air from the centrally located fan is redirected from its normal centrifugal path upward by a deflector to provide a separate path below the deflector for the air to flow to the filter. The air flow path is thus reversed within the fan enclosure and above the filter, and within the port since the trough-shaped baffle is within the outlet port for air flow from the fan. While the noted patent provides a curvilinear guide defined by the trough to ease the flow transition from one direction to another, the flow direction is undoubtedly reversed and this requires more energy than a linear, or non-reversed path. The industry desires lower energy costs and units using 100 watts or less have been a major goal in the industry. The present invention through creation of a linear, non-reversing air flow path that has the pressurized air enter the fan enclosure outlet ports only from directly above and/or the sides and other means to be described hereinafter reaches this goal, while maintaining a high filtering efficiency of 99.999% at 0.12 micron particle size, air flows of 90 FPM, and a reduced BTU output of approximately only 200 BTU/hr to lessen the refrigeration load in the clean room. 
     It is an object, therefore, of the present invention to provide an improved fan filter unit for filtering air entering a clean room, a surgery, or other meticulously controlled environment. It is a further object to provide fan filter units that are more filtering-efficient, more energy efficient to lower electrical costs, less demanding of cooling capacity, and less noise generating for a quieter workplace; and withal simply installed. A still further object is to provide a fan filter unit that uses a system of baffles arranged to conduct linear air flow laterally or vertically into outlet ports from the fan enclosure and to block reverse flows in the enclosure or in the outlet port where the air is returned in the direction whence it came. Another object is to provide a fan filter unit achieving higher filtering efficiency and increased energy efficiency through the use of separator-less filter media packs of increased pleat depth and greater pleat density. A further object is to provide a mating fan filter unit enclosure and filter media containing frame that are conjoined above the filter media to define a plenum, one or the other of the enclosure and frame carrying air flow distributors opposite the outlet ports. 
     These and other objects of the invention to become apparent hereinafter are realized in a higher filtering efficient, lower energy consuming, less heat generating, and lower noise generating fan filter unit for flowing air filtered through a higher efficiency particulate air filter into a clean room, the fan filter unit being normally horizontally disposed and comprising a longitudinally and laterally extended enclosure having an air inlet and an air outlet, a high efficiency particulate air filter unit in air-flow communication with the enclosure outlet across a plenum defined by the enclosure and the air filter unit, a motorized fan in air flow communication with the enclosure inlet and the outlet, the fan being supported centrally within the enclosure, the enclosure outlet comprising a longitudinally spaced ports and laterally spaced ports, the ports lying in a normally horizontal common port plane below the fan and collectively being of sufficient cross-sectional area to pass without substantial back pressure the air flow generated by the motorized fan, individual baffle structures extending substantially normal to the common port plane adjacently before each port and between the fan and the port, the baffle structures being arranged to block all direct air flow from the motorized fan into the ports, whereby air flow from the ports is linear and free of reversal in flow direction within the enclosure and within the ports. 
     In this and like embodiments, typically, the enclosure comprises side walls, a top wall defining the inlet and a bottom wall defining the outlet ports, the air filter unit comprising a frame attached to the fan unit, and a filter, the filter being spaced from the enclosure bottom wall in plenum-defining relation, the baffle structures extend from the enclosure bottom wall vertically a height sufficient to effect the blocking of all direct air flow from the motorized fan into the ports, the baffle structures extend from the enclosure bottom wall vertically a height of at least 25% of the distance between the bottom wall and the enclosure top wall, or the baffle structures extend from the enclosure bottom wall to the enclosure top wall, the laterally spaced ports have individual baffle structures of a V-shape in a plane parallel to the plane of the ports, the V-shape being open to the motorized fan, the longitudinally spaced baffle structures are triangular in cross-section in a plane parallel to the plane of the outlet ports, the baffle structure bases being immediately adjacent their respective ports, the laterally spaced ports have individual baffle structures of a V-shape in a plane parallel to the plane of the ports, the V-shape being open to the motorized fan, and the enclosure side walls are of substantially the same length, the longitudinally spaced baffle structures being triangular in cross section and having their bases immediately adjacent their respective ports. 
     In a further embodiment, the invention provides a high filtering efficiency, low energy, low noise fan filter unit for flowing air filtered through a high efficiency particulate air filter into a clean room comprising an enclosure having side walls, a top wall defining an air inlet and a bottom wall defining a plurality of laterally and longitudinally spaced outlet ports, the side walls being adapted to attach an air filter unit including a filter to be spaced from the enclosure bottom wall in plenum defining relation, and a plurality of air flow distributors supported between the filter unit bottom wall and the air filter, the air flow distributors being apertured and arranged to guide air flow from each outlet port to the filter. 
     In this and like embodiments, typically, there is further included an air filter unit, and the enclosure is separately formed from the air filter unit, the enclosure having a skirt continuation of the side walls beyond the bottom wall for enclosing the plenum, the air flow distributors being supported by the enclosure skirt within the plenum. Or, the air flow distributors are supported by the air filter unit within the plenum. Typically, an air filter unit is included that comprises a unit frame and a filter comprising a filter media pack sealably contained within said frame, said filter media pack having no separators, a pack depth of about 5 inches and a pleat density of about 5-7 pleats per inch. 
     The invention further provides a fan filter unit comprising an enclosure having side walls, a top wall defining an inlet and a bottom wall defining a plurality of laterally and longitudinally spaced outlet ports, the side walls being adapted to attach an air filter unit including a filter to be spaced from said enclosure bottom wall in plenum defining relation, and a plurality of air flow distributors supported between said filter unit bottom wall and the air filter said air flow distributors being apertured and arranged to guide air flow from each said outlet port to said filter, there is further included the air filter unit, and the enclosure is separately formed from the filter unit, and the enclosure has a skirt continuation of the side walls beyond the bottom wall for enclosing the plenum, the air flow distributors being supported by the enclosure skirt within the plenum, or the air flow distributors are supported by the air filter unit within the plenum. 
     In a further embodiment, the air filter unit comprises a unit frame and a filter media pack sealably contained within the frame, the filter comprising a filter media pack having no separators, a pack depth of about 5 inches and a pleat density of about 5-7 pleats per inch. 
     In a still further embodiment, the invention provides a high filtering efficiency, low energy, low noise fan filter unit for flowing air filtered through a high efficiency particulate air filter into a clean room, the fan filter unit comprising a longitudinally and laterally extended enclosure comprising four sides, a top wall and a bottom wall, a central air inlet in the top wall, a series of perimetrically distributed air outlet ports through the bottom wall, a skirt continuation of the enclosure side walls beyond the bottom wall, a high efficiency particulate air filter unit comprising a frame attached to the enclosure skirt continuation, a high efficiency particulate air filter sealably mounted within the frame and defining a plenum with the enclosure bottom wall, a motorized fan in air flow communication with the enclosure inlet and the plenum through the outlet ports, the fan being supported centrally within the enclosure, the outlet ports collectively being of sufficient cross-sectional area to pass without substantial back pressure the air flow generated by the motorized fan, an individual baffle structure adjacent each the outlet port, the baffle structures extending vertically a height equal to the distance between the enclosure bottom wall and the enclosure top wall, whereby the outlet ports are closed by adjacent baffle structure to all but lateral entry of air flow from the motorized fan, air flow from the ports thereby being linear and free of reversal in flow direction within the enclosure and within the ports. 
     In this and like embodiments, typically, the enclosure side, top and bottom walls and the baffle structures define air directing surfaces, the air directing surfaces being covered with sound-absorbing medium, the enclosure skirt continuation terminates in an inwardly turned flange, the filter unit frame having a shoulder abutting the flange, and including also a fastener attaching the filter unit shoulder to the skirt continuation flange in abutting relation, the outlet ports are sized and located to direct motorized fan pressurized air within the enclosure substantially uniformly to the plenum, there is also included air flow distributors within the plenum spaced from the air filter and opposite the outlet ports, the air flow distributors comprising a series of plates extending normal to the skirt continuation in skirt continuation supported relation or the air flow distributors comprise a series of plates extending normal to the air filter frame in air filter frame supported relation, the outlet ports include a pair of laterally spaced outlet ports and a pair of longitudinally spaced outlet ports, and the baffle structures include a pair of laterally opposed baffle structures that have a V-shape in a plane parallel to the plane of the outlet ports, the V-shape being open to the motorized fan, and the baffle structures include a pair of longitudinally opposed baffle structures that triangular in cross-section in a plane parallel to the plane of the outlet ports, the baffle structure bases being immediately adjacent their respective ports. 
     In a further embodiment wherein the fan filter unit is substantially even-sided, the invention provides a high filtering efficiency, low energy, low heat output, low noise fan filter unit in which the enclosure side walls are of substantially the same length, the baffle structures being triangular in cross section and having their bases immediately adjacent their respective ports. 
     In yet a further embodiment the invention provides a ceiling-suspendable, high filtering efficiency, low energy, low noise fan filter unit for flowing air filtered through a high efficiency particulate air filter into a room, 
     the filter fan unit comprising a generally horizontally disposed longitudinally and laterally extended enclosure for a centrally positioned motorized fan from which a supply of pressurized air is circularly distributed, 
     the enclosure having 
     a top wall blocking air ingress into the enclosure except via the motorized fan, 
     an air impervious side wall, and 
     a bottom wall defining the upper boundary of a plenum below the enclosure, the enclosure being adapted to sealably mount an air filter unit comprising an air filter pack sealably mounted in a frame to define the lower boundary of the plenum, 
     the bottom wall further defining 
     a first set of spaced outlet ports and a second set of spaced outlet ports disposed at right angles to the first set of outlet ports, 
     the outlet ports communicating the interior of the enclosure with the plenum, 
     the outlet ports being sized and distributed to allocate portions of the pressurized air supply to laterally opposite and longitudinally opposite locations in the plenum for substantially uniform pressure air flow into the plenum, 
     the enclosure having disposed therein a generally vertical baffle structure immediately adjacent each outlet port extending normal to the plane of the outlet port and horizontally spaced from the motorized fan, 
     each baffle structure extending from the enclosure bottom wall vertically a height of at least 25% of the distance between the bottom wall and the enclosure top wall for at least the transverse extent of its adjacent port along the side wall, 
     the enclosure walls and baffle structures having sound-deadening surfaces where contacted with flowing air, 
     whereby the pressurized air flows from the ports is linear and free of reversal in flow direction within the enclosure and within the ports. 
     In this and like embodiments, the enclosure can be rectangular or square with have four substantially equal length wall sections forming the side wall. Typically, one of the spaced ports is located at each wall section and substantially intermediate the ends thereof, the outlet port being generally rectangular and substantially abutting its wall section, at each outlet port the baffle structure is generally triangular in horizontal cross-section for the height of the baffle structure, with the base of the triangle substantially abutting its adjacent outlet port and at least equaling in its horizontal extent the horizontal extent of the adjacent outlet port, there is further included a filter pack having a pack of about 5 inches in depth at a density of about 5-7 pleats per inch, a ΔP of about 0.27 inch of water gauge at 100 FPM, and a filtering efficiency of about 99.999% at 0.12 micron particles, the fan filter unit having an energy consumption of about 100 watts, air flows of about 90 FPM through the filter pack, and a heat output of approximately 200 BTU/hour. 
     Further in this and like embodiments, a secondary baffle or air flow distributor can be disposed substantially opposite each outlet, the distributor having air passages comprising a plurality of air-passing apertures, such as slots or openings of circular, oblong or other polygonal shape. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be further described in conjunction with the attached drawings in which: 
     FIG. 1 is a top plan view of the fan filter unit with the top wall partially broken away to show the underlying parts; 
     FIG. 2 is a bottom plan view of the fan filter unit without the attachment of the filter unit; 
     FIG. 3 is a view in vertical cross-section along the long axis of the fan filter unit and attached filter unit; 
     FIG. 4 is a view taken on line  4 — 4  in FIG. 3; 
     FIG. 5 is a view like FIG. 3 of an alternate form of the invention; 
     FIG. 6 is a view taken on line  6 — 6  in FIG. 5; and, 
     FIG. 7 is a view like FIG. 5 of a further alternate form of the invention; 
     FIG. 8 is a view taken on line  8 — 8  in FIG. 7; and, 
     FIG. 9 is a top plan view of a further alternate form of the invention, the top wall having been removed. 
    
    
     DETAILED DESCRIPTION 
     With particular reference now primarily to FIGS.  1 - 4 , the invention fan filter unit  10  provides for flow of filtered air into a space or room (not shown) and comprises a generally rectangular enclosure  12  having a wall  14  with, in this embodiment, relatively shorter end portions  16 , relatively longer side portions  18  connecting the end portions, and an Intermediate portion  22  connected to and spaced from the end portions and the side portions. A fan and motor combination  24  is mounted in the enclosure  12  opposite the enclosure intermediate portion  22 . A bottom wall  26  is secured to the side wall, as is a top wall  28  that cooperates with the other walls in enclosing the enclosure  12 . Bottom wall  26  defines the upper wall of plenum  32  (FIG.  3 ). Bottom wall  26 , top wall  28  and side wall  14  define the enclosure  12  shown here as rectangular but which can be of another shape, see FIG.  9 . Enclosure  12  is of a predetermined height and generally encloses the fan and motor combination  24  mounted therein. There is an inlet  20  into the enclosure  12  formed centrally of the top wall  28  through which air is drawn to the motorized fan  24 , e.g. using an external rotor motor blower having a nominal 1 amp draw at 110 VAC/60 Hz, and over 750 CFM at zero static pressure. All walls are covered with sound-absorbing material  30  within the enclosure  12 . Corners  29  of the enclosure  12  are filled with sound-dampened wedges  31  to limit turbulence in the air flow and noise. 
     A plurality of perimetrically distributed outlet ports  34 ,  36 , are pierced through the enclosure bottom wall  26  from the enclosure  12  to the plenum  32  to provide for flow of pressurized air from the fan and motor combination  24  into the plenum. Laterally spaced ports  34  are provided at the longer side wall portions  18 , and longitudinally spaced ports  36  at the shorter end wall portions  16 . The ports  34 ,  36  are sized in depth (extent of opening from the adjacent wall portion into the enclosure) and width (extent of opening along the adjacent wall portion) to permit substantially untrammeled air flow free of back pressure attributable to the outlet port. The ports can have any configuration permitting free air flow. Air flows of a nominal 90 FPM are realized, with an energy consumption of about 100 watts, at a filtering efficiency of 99.999% at 0.12 micron particles using a 5 inch deep filter pack of 5-7 pleats per inch where the filter pack has a ΔP of 0.27 inch of water gauge at a velocity of 100 FPM. 
     Within the enclosure  12  and adjacent the respective outlet openings  34 ,  36  a series of baffle structures  48 ,  52  are provided. Baffle structures  48  comprise wedges of triangular horizontal cross-section, with the base  53  of the wedge substantially abutting the inwardmost edge  35  of the outlet port  36  opposite it. The baffle structure wedge base  53  extends at least the width of the outlet port  36  and preferably about 5 to 20% more than that width, evenly divided relative to the port. Baffle structures  48  covered with further sound damping material  30  such as a sound-absorbing foam, are arranged as shown with their leading narrow edge  49  facing the inward to cut the pressurized air driven centrifugally from the fan and motor combination  24  into two parts, left and right. The baffle structures  48  are of a height h to extend the full distance d between the bottom wall  26  and the top wall  28  of the enclosure  12  so that h=d. Thus there is no air flow space between the baffle structures  48  and the enclosure top wall  28  or bottom wall  26 . Air flow, accordingly, passes only around the baffle structures  48 , not over or under them. The air flow, once parted by the wedge leading edge  49 , is guided laterally along the wedging surfaces  47  of the baffle structures  48  and thence around the trailing edges  50  into the adjoining outlet port  36  from either side of the baffle structure; other air flows are blocked. It will be noted that the air flow is thus linear and free of reversal of flow direction within the enclosure  12  and within the outlet ports  34 ,  36 . 
     Baffle structures  52  are arcuate in horizontal cross-section and positioned such that their convex sides  55  abut the laterally spaced ports  36  and their concave sides  57  oppose the fan  24 . The baffle structures  52  extend a distance parallel to the side walls  18  greater than the like extent of the adjacent outlet ports  36  and preferably about 5 to 20% greater and are centered on the outlet port  36  center. Baffle structures  52  have a height h equal to the distance d between the enclosure  12  bottom wall  26  and top wall  28  and thus pass no air flow over or under themselves but only around them and laterally into the outlet ports  36 . Baffle structures  52  are also covered with a sound damping material  30  such as a sound-absorbing foam. As arranged, baffles  52  guide air flow from the motorized fan  24  along a linear flow along the baffle structure face  59  and around the structure corners  61  into the outlet ports  36 . 
     The just described fan filter unit  10  is coupled to a filter unit  60 . Filter unit  60  comprises a generally rectangular frame  62  formed of walls  64 , and a filter pack  66  comprised of filter media  68  sealably attached to the frame walls  64  to block flow of unfiltered air flow through the filter unit. The present invention for maximum filtering efficiency and optimum energy consumption uses a filter pack  66  comprised preferably of filter media pleats of about 5 inches in depth, with no separators between the successive pleats and a pleat density of about 5-7 pleats per inch. Other sizes, densities, styles and types of HEPA, UPLA or other high efficiency filter can be used with commensurate results. 
     Filter unit  60  has a perimetrical flange  72  (exaggerated in this view for clarity) inwardly turned around the top of its walls  64 . Fan filter unit  10  has a mating inwardly turned flange  74  (also exaggerated) on a skirt continuation  76  of the fan filter unit wall  14  that projects beyond the portion of wall  14  that encloses enclosure  12 . As shown in FIG. 3, fan filter unit  10  flange  74  overlies the upper flange  72  of the filter unit  60 . The fan filter unit  12  and filter unit  60  are fastened together by bolts or screws, or by a tape that doubles as a sealing tape  78  pressed over the joint  82  between the units and onto the edge margins  84 ,  86  of the joint. 
     The filter pack  66  upper surface  88  defines with the fan filter unit bottom wall  26  the plenum  32 . Air flow from the outlet ports  34 ,  36  enters the plenum  32  and encountering the lower flow rates of the filter pack  66  establishes an increased air pressure within the plenum. To better ensure the even flow of air in the plenum  32  to the filter pack upper surface  88 , a series of air flow distributors  92 ,  94  are provided. Air flow distributors  92  are flat plates, typically of aluminum, that are cantilevered or otherwise supported at the laterally opposed outlet ports  36  in the air flow stream through the ports  34  in position to deflect somewhat the downcoming air from immediately passing to the filter pack upper surface  88  in a manner that would unbalance the air pressure on that surface in favor of surface areas immediately opposite the outlets  34 ,  36 . Distributors  92  and  94  are similar in construction, support and function, but for the air flow downcoming from the longitudinally opposed outlet ports  34  in the case of distributor  94 . In FIGS. 3 and 4, the air flow distributors  92 ,  94  are shown attached to the fan filter unit wall skirt continuation  76  just above the inturned flange  74 , so that the fan filter unit  10  carries the air flow distributors  92 ,  94 . Preferably the air flow distributors  92 ,  94  are apertured with slots  93 ,  95  as shown FIG. 1 (viewed through outlet ports  34 ,  36 ). 
     In FIGS. 5 and 6, in which like parts are given like numerals, the air flow distributors  92 ,  94  are shown attached to the filter unit  60 , below the joint  82  between the fan filter unit  10  and the filter unit  60  so that the filter unit carries the air flow distributors as may be desirable in certain applications or for manufacturing reasons 
     In FIGS. 7 and 8, in which like parts are given like numerals, an embodiment is shown in which the baffle structures  148 ,  152  are of less than full height within the enclosure  12 , so that air flow is not only around the edges of the baffles, but also over the top, as a waterfall, into the outlet ports  34 ,  36 . Like the previous embodiments, the air flow in this embodiment is non-reversing within the enclosure  12  and the ports  34 ,  36 . More particularly, within the enclosure  12  and adjacent the respective outlet openings  34 ,  36  a series of baffle structures  148 ,  152  are provided. Baffle structures  148  comprise wedges of triangular horizontal cross-section, with the base  153  of the wedge substantially abutting the outlet port  36  opposite it. The baffle structure wedge base  153  extends at least the width of the outlet port  36  and preferably about 5 to 20% more than that width, evenly divided relative to the port. Baffle structures  148  covered with further sound damping material  30  such as a sound-absorbing foam, are arranged as shown with their leading narrow edge  149  facing the inward to cut the pressurized air driven centrifugally from the fan and motor combination  24  into two parts, left and right. The baffle structures  148  are of a height ht to extend about one-half the full distance d between the bottom wall  26  and the top wall  28  of the enclosure  12  so that ht=50%×d. The height ht can be from about 25% of d up to 75% or as shown in previous embodiments 100% of d (ht=h=d). In this embodiment there is more or less air flow space between the baffle structures  148  and the enclosure top wall  28 . Air flow, accordingly, passes not only around the baffle structures  148 , but also over them. The air flow parted by the wedge leading edge  149 , is guided laterally along the wedging surfaces of the baffle structures  148  and thence around the structure into the adjoining outlet port  36  from either side of the baffle structure. Air flow is also passed over the upper edges  109  of the baffle structures  148  and mixes with the lateral flow coming around the vertical edges. It will be noted that the air flow is thus linear and free of reversal of flow direction within the enclosure  12  and within the outlet ports  34 ,  36 . 
     Baffle structures  152  are arcuate in horizontal cross-section (Cf. Item  52  in FIG. 1) and positioned such that their convex sides  155  abut the laterally spaced ports  36  and their concave sides  157  oppose the fan  24 . The baffle structures  152  extend a distance parallel to the side walls  18  greater than the like extent of the adjacent outlet ports  36  and preferably about 5 to 20% greater and are centered on the outlet port  36  center. Baffle structures  152  too have a height ht equal to less than the distance d between the enclosure  12  bottom wall  26  and top wall  28 , ranging from a least about 25% of d to 75% or more up to 100% as in previous embodiments. It is not necessary that the height ht of the baffle structures  152  be equal to the height ht of the other baffle structures  148  within the same enclosure  12 . As described for baffle structures  148 , structures  152  pass air flow over themselves as well laterally into the outlet ports  36 . Baffle structures  152  are also covered with a sound damping material  30  such as a sound-absorbing foam. As arranged, baffles  152  guide air flows from the motorized fan  24  along a linear flow along the baffle structure and around the structure corners and laterally into the outlet ports  36 , as well as over the upper edges  111  and linearly into the ports  36 . 
     In FIG. 9, in which like parts have like numerals plus  200 , a square form of the invention fan filter unit  210  is shown. The motorized fan  224  is supported in the center of the enclosure  212  formed of top wall  228 , bottom wall  226 , and sidewalls  214 . Baffle structures  248 , all triangular in horizontal cross section, are used to divide and guide the air flow to enter outlet ports  234 ,  236  laterally only and to pass the air flow linearly along the baffle structure side walls  247  without reversal of direction within the enclosure  212  or the outlet ports  234 ,  236 . A filter unit (not shown) congruent with the fan filter unit  210  is attached to the fan filter unit as in previous embodiments. 
     The present invention thus provides improved fan filter units that are more filtering efficient, more energy efficient to lower electrical costs, less noise generating for a quieter workplace, and simply installed. The fan filter units have a system of baffles arranged to conduct linear air flow laterally and vertically into outlet ports from the fan enclosure and to block reverse flows in the enclosure and in the ports. The fan filter unit achieves increased filtering efficiency through the use of separator-less filter media packs of increased depth and greater pleat density, and more energy efficiency through the noted baffle design so that energy consumption is about 100 watts and heat output is low at about 200 BTU/hour. The fan filter units comprise a mating fan filter unit enclosure and filter media containing frame that are conjoined above the filter media to define a plenum, one or the other of the enclosure and filter frame carrying air flow distributors opposite the outlet ports. The foregoing objects are thus met.