a vacuum / filter apparatus is illustrated in fig1 and referred to generally as an evacuator 10 . a preferred embodiment of this apparatus is particularly adapted for the evacuation and filtration of surgical smoke . such smoke is typically developed when electrosurgical apparatus and lasers are used for cutting and cauterizing . the evacuator 10 is relatively small in size and light in weight to enhance its portability . this makes it particularly desirable for use in small rooms , such as doctor &# 39 ; s offices , and particularly easy to store when not in use . in the illustrated embodiment , the evacuator 10 includes an enclosure 12 which is formed from a base assembly and an overlying cover assembly 16 . the base assembly 14 includes a front panel 18 as well as a base frame 21 and rear panel 23 which are best shown in fig2 . the cover assembly 16 includes a top 25 and downwardly extending side panels 27 and 30 . a handle 32 facilitates carrying of the evacuator 10 when the cover assembly 16 is attached to the base assembly 14 . a power cord 34 enters the rear panel 23 and provides suitable electrical power , such as 110 volt ac to the evacuator 10 . a power switch 35 is provided on the front panel 18 to energize the evacuator 10 . a bracket 37 can be attached to the rear panel 23 to facilitate wrapping the cord 34 in a confined configuration thereby enhancing the portability of the evacuator 10 . an inlet port 36 is also provided in the front panel 18 and is configured to receive a front loaded filter 38 . an inlet hose 41 is , typically provided for connection to the filter 38 and extension to the operative site which is originating the surgical smoke . the hose 41 may have a length such as six feet and an internal diameter such as 7 / 8 inch . at the distal end of the hose 41 , a two foot section of quarter inch tubing may be added to facilitate desirable orientation of a suction tip 43 . interiorly of the evacuator 10 , an upstanding partition 45 is fixed to the base frame 21 and provides a support for an air pump motor 47 . the motor 47 is positioned to facilitate air flow through a primary air channel extending from the inlet port 36 to an outlet port 49 , best shown in fig3 . the outlet port 49 in a preferred embodiment consists of a plurality of louvers which facilitates the exhausting of filtered air from the evacuator 10 . between the ports 36 and 49 , a primary air flow channel extends though a filter housing 50 , a seal 52 and a mesh 53 which is of particular interest to the present invention . the primary channel extends rearwardly of the mesh 53 through an impeller housing 54 , and the motor 47 . between the motor 47 and the outlet port 50 , a series of baffles 56 are provided in the form of a torturous path defined by sheets of foam 58 . the baffles 56 are oriented in the conventional manner to direct air flow along the surface of the foam sheets 58 as illustrated generally by the arrows 60 in fig3 . these baffles 56 not only enhance the filter characteristics of the evacuator 10 but also greatly reduce the sound associated with its operation . in the illustrated embodiment , the primary channel is designated generally by the arrows 61 . in a preferred embodiment the filter 38 is specially configured for receipt through the port 36 into the filter housing 50 . the filter 38 has a case 62 , which is generally cylindrical in shape . at its forward end , the case 62 tapers conically to a friction fit which is configured to receive the distal end of inlet hose 41 . at its rearward end , the case 62 of the filter 38 is open . when the filter 38 is operatively inserted horizontally through the port 36 , the open end at the rearward end of the filter 38 seats against the seal 52 . this seal 52 has a generally toroidal configuration which defines a hole 63 along the primary channel 61 . in a preferred embodiment , the filter case 62 encloses an ultra low penetration air ( ulpa ) filter material 62a capable of filtering 99 . 999 % of particles greater than 0 . 1 micron in size . the filter material may also include charcoal which tends to adsorb noxious odors . although the filter 38 is much smaller than those associated with operating room evacuators , it nevertheless has a cumulative run time of approximately 20 minutes which is deemed to be sufficient for outpatient surgery . the motor 47 is energized by electrical power from the power cord 34 which is interrupted by the on / off switch 35 . when the filter 38 is inserted through the inlet port 36 , operation of the motor brings the rear end of the filter case 62 into sealing engagement with the foam 52 . an impeller ( not shown ) in the housing 54 creates a vacuum drawing air through the inlet hose 41 , the filter 38 , the hole 63 in the mesh 53 . this air in the primary channel is cleaned by the filter 38 and quieted by the baffles 56 before it is exhausted through the outlet port 50 . in a preferred embodiment the motor 47 creates a vacuum equivalent to 64 inches of water with a flow of 68 cubic feet per minute without load . when the load is applied , this flow drops to 3 cubic feet per minute . operation of the motor 47 under load creates considerable heat which , under normal conditions , is dissipated by air flowing through the primary channel . for purposes of safety , a thermostatic cut - out 70 can be provided to interrupt power to the motor 47 at an elevated temperature such as 235 ° f . as an alternative to driving the motor 47 to an overheated condition , provision is made in the present invention for bleed air to cool the motor when the primary air flow channel is clogged or blocked . this typically occurs when the filter 38 becomes blocked by filtered particles . this bleed air can be introduced into the evacuator 10 through any port extending to the outside . in a preferred embodiment the bleed air flows through a secondary channel illustrated by the arrows 72 . this secondary channel begins at the inlet port 36 and passes circumferentially of the filter 38 between the filter housing 50 and the inside of the case 62 . the bleed air exits this circumferential space thorough a hole 76 in the housing 50 and a hole 78 in silencing insulation 81 which surround the housing 50 . this insulation 81 can be held in place around the filter housing 50 by a strap 82 . in a preferred embodiment , the inside diameter of the housing 50 is 3 . 250 inches , and the outside diameter of the filter case 62 is 3 . 125 inches . it follows that the circumferential space between the filter 38 and the housing 50 which defines the initial portion of the secondary channel 72 has a radial dimension of 0 . 0625 or 1 / 16 inch . as the bleed air passes through the hole 78 in the insulation 81 , it moves into the large interior space defined by the enclosure 12 . from this location , the bleed air enters the primary channel 61 forwardly of the motor 47 . in this manner , the bleed air passes through the motor 47 to facilitate the dissipation of heat . in a preferred embodiment , the bleed air enters the primary channel 61 by way of the mesh 53 . in the mesh 53 the secondary channel 72 is characterized by a non - woven structure consisting of a first plurality of parallel fibers 85 which are individually attached to a second plurality of parallel fibers 87 . since the mesh 53 is non - woven , both the fibers 85 and 87 are straight and extend in respective parallel planes . the fibers 85 extend at a particular angle , such as 60 °, with respect to the fibers 87 . since one of the purposes of the second fibers 87 is to maintain the first fibers 85 in their generally parallel relationship , it may be desirable to maximize the points of contact between the fibers 85 and 87 . with this configuration , the mesh 53 defines a plurality of passages 90 which have a cross - sectional configuration similar to the dotted rectangle 92 illustrated in fig6 . these passages 90 extend generally parallel to each other between adjacent pairs of the fibers 85 . with the fibers 85 defining the passages 90 , the cross fibers 87 function primarily to hold the passage fibers 85 in a separated parallel relationship . the mesh 53 is representative of any structure which combines the first channel 61 and the secondary channel 72 at an intersection which precedes the motor 47 . although this combining means is provided int eh form of a non - woven mesh in the illustrated embodiment , it will be apparent that it can take other shapes indifferent embodiments . for example , the mesh may comprise a woven structure which would provide more torturous paths for the passages 90 . in general , it has been found that a structure providing multiple passages 90 is preferred over a structure providing only a single passage . it is also suggested that generally straight passages 90 are preferred to reduce the noise level of the evacuator 10 . in a preferred embodiment , the mesh 53 is formed of a polypropylene polycarbonate material . the fibers 85 , 87 have a diameter of about 0 . 040 inches so that the total thickness of the mesh 53 is approximately 0 . 080 inches . both the fibers 85 and the fibers 87 are separated by a distance of 0 . 032 inches . it follows that the cross - sectional dimensions of the passages 90 , the dimensions of the rectangle 92 , are approximately 0 . 040 inches by 0 . 132 inches . this mesh 53 is manufactured and marketed under the trademark naltex by nalle plastics , inc . of austin , tex . this particular mesh 53 is of advantage to the present invention because of its narrow thickness , and the multiplicity of passages which it provides at the intersection of the primary channel 61 and secondary channel 72 . providing a single hole at this intersection could increase air velocity , thereby dramatically increasing the noise associated with the flow of air . the multiplicity of passages greatly reduces this noise level in the evacuator 10 . thus the mesh 53 contributes greatly to the objectives of the evacuator 10 , namely small size and quiet operation . the mesh 53 also facilitates assembly of the evacuator 10 since it is merely sandwiched between the foam seal 52 and the partition 45 which supports the motor 47 . given the foregoing criteria , this miniature evacuator 10 is particularly adapted for use in small spaces such as a doctor &# 39 ; s office . of course it will be apparent that these criteria can be modified in other embodiments to accomplish the same objectives . for example , the mesh 53 can be configured with many different sizes and fiber orientations . the bleed air can be introduced into the enclosure 12 along many different channels . alternative channels may not begin at the inlet port 36 and may not extent circumferentially in the space between the housing 50 and the filter 38 . with the wide variety of variations available within this concept , one should not attempt to restrict the invention merely to those embodiments which are illustrated and disclosed but should ascertain the scope of the invention only with reference to the following claims .