Patent Publication Number: US-11662279-B2

Title: Portable air sampler

Description:
RELATED APPLICATIONS 
     This is a continuation-in-part of U.S. application Ser. No. 15/243,403, filed Aug. 22, 2016, which is a continuation of U.S. Design Application No. 29/574,405, filed Aug. 15, 2016, which claims priority to provisional Application No. 62/375,274, filed Aug. 15, 2016. This application also claims priority to provisional Application No. 62/627,502, filed Feb. 7, 2018. The entire contents of those applications are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a device and method for collecting and analyzing air samples in a controlled, indoor environment. In particular, the present invention relates to devices and methods for collecting, processing, and analyzing air samples in clean rooms and remotely monitoring, logging, and controlling the sampling device. 
     Background of the Related Art 
     Controlled environments such as hooded areas and clean rooms (collectively referred to as “clean rooms”) found in manufacturing, research, and other facilities are typically classified into two broad categories based on the static air pressure inside the rooms relative to atmospheric pressure and/or based on the air pressure in spaces adjacent the clean rooms. A positive air pressure room is maintained at an absolute air pressure greater than atmospheric pressure, greater than the air pressure in spaces adjacent the clean room, or both. The positive air pressure in such rooms is provided by pumping filtered and/or conditioned air into the rooms and controlling the flow of air out of the rooms. The adjacent spaces, which may be manufacturing facilities or offices, are typically maintained at or close to atmospheric pressure by heating, ventilation, and air conditioning (HVAC) systems, or by providing an opening to the environment that allows the adjacent spaces to equilibrate with atmospheric pressure. Thus, air flowing from the positive pressure clean room will flow toward the lower pressure in adjacent rooms or to the atmosphere. 
     When a positive air pressure clean room is breached, air flowing to adjacent spaces or the atmosphere is generally not a problem as long as airborne contaminants present in the clean room do not pose a potential adverse health effect to people in the adjacent spaces. Typically, the air inside clean rooms in which electronics, aerospace hardware, optical systems, military equipment, and defense-related research are manufactured or conducted may not contain airborne gases, vapors, and particulate matter at concentrations that present a safety or health concern to human health or the environment. However, that is not always the case, as other operations within those industries may generate contaminants that are above acceptable levels and, therefore, must be prevented from escaping the clean room without treatment. 
     A negative air pressure room is maintained at an absolute air pressure that is either less than atmospheric pressure, less than the air pressure in spaces adjacent the clean room, or both. The negative pressure is maintained by pumping air out of the room at a rate faster than that at which filtered and/or conditioned air is pumped into the room. Negative pressure rooms are often used when there is a concern that contaminants in the air in the room may pose a potential health threat to human health in adjacent spaces or the environment. 
     Notwithstanding the human health and environmental implications, certain types of manufacturing and research operations must be conducted within a positive air pressure clean room to satisfy regulatory requirements and industry-adopted good manufacturing and laboratory quality control standards. For example, state and federal regulations, including those promulgated by the National Institute for Occupational Safety and Health (NIOSH), may necessitate the use of positive or negative pressure clean rooms. 
     In particular, the U.S. Food &amp; Drug Administration (FDA) requires that pharmaceutical production be done within the confines of clean rooms that provide for the validation and certification that manufactured batches of pharmaceutical products are being produced in a sanitary environment. 
     Various FDA regulations and standards also specify requirements for air sampling and/or air monitoring equipment to be used inside clean rooms to verify or validate the cleanliness of the facility during certain drug manufacturing activities. The regulations also provide for electronic data recording, accuracy, precision, and record-keeping relating to monitoring the air quality within clean rooms. Similar requirements are imposed on other industries, such as the biotechnology industry. 
     A number of patents and published applications teach systems for air sampling and monitoring in clean rooms and for monitoring and controlling one or more air sampling devices from a central location, such as for instance U.S. Pat. Nos. 9,285,792, 9,063,040, 9,046,453, and U.S. Patent Publication No. 2016/0061796. 
     In addition, the Assignee Veltek Associates Inc. offers the portable sampling device shown in  FIG.  8   . As shown, air is drawn in through an atrium  50 , across an agar media plate  52 , and through an opening  54  at the bottom of the atrium rest. After passing through the hole  54 , the air is drawn through a large fan  56  and exhausted through the body of the unit across the electronics and out of the bottom  58 . The device is configured to operate at a constant fan speed that is proportional to the desired flow rate. 
     SUMMARY OF THE INVENTION 
     An air sampling device samples air in a controlled environment. The device includes a housing body having a top and a side. An opening is located at the top of the housing body. A retaining assembly retains a sampling device and atrium. The retaining assembly is located at the top of the housing body about the opening. A plenum has a top end and a bottom end, with the top end coupled to the top of the housing body about the opening so that the plenum is in flow communication with the opening. A mass flow meter has an input and an output, with the input coupled to the bottom end of the plenum and in flow communication with the bottom end of the plenum. A blower is located inside the plenum and is configured to draw air past the sampling device, through the opening, through the plenum, and through the mass flow meter. The mass flow meter detects a flow rate of air through the mass flow meter. And a controller receives the detected flow rate from the mass flow meter and controls a speed of the blower in response to the detected flow rate. The controller increases the speed of the blower if the detected flow rate is lower than a desired flow rate, and decreases the speed of the blower if the detected flow rate is higher than a desired flow rate. 
     An air sampling device for sampling air that comprises a housing body that has a top, a side, and an opening at the top; a retaining assembly configured to retain a sampling device, wherein the retaining assembly may be located at the top of the housing body about the opening; a plenum that has a top end, a bottom end, and a longitudinal length defined therebetween, wherein the top end may be coupled to the housing body about the opening such that the plenum is in flow communication with the opening, and the plenum may be configured for receiving air flow generally from the top end to the bottom end generally along the longitudinal length; a flow connection may be coupled to the bottom end of the plenum; a mass flow meter that has an input and an output, wherein the input may be coupled to the flow connection, and the mass flow meter may be in flow communication with the plenum via the flow connection; and a blower in association with the plenum. The blower may be configured to draw air past the sampling device, through the opening, and through the plenum, such that a measuring portion of the air in the plenum flows through the flow connection and through the mass flow meter, wherein the mass flow meter is configured to measure the flow rate of the measuring portion of the air drawn through the flow connection. 
     A method for sampling air, comprising to step of drawing air across a media plate located at an outside of a housing body and through a plenum inside of the housing body; diverting a measuring portion of the air in the plenum to a mass flow meter wherein the measuring portion of the air is proportional to the air in the plenum; and measuring at the mass flow meter, a detected flow rate of the measuring portion of the air. The method may further comprise the step of comparing the detected flow rate of the measuring portion of the air to a desired flow rate; controlling the speed of the flow of the air through the plenum based on the comparison between the detected flow rate and the desired flow rate; increasing the speed of the flow of the air of the detected flow rate if lower than the desired flow rate or decreasing the speed of the flow of air of the detected flow rate if higher than the desired flow rate. In certain embodiments, a flow connection may be coupled to the plenum which diverts the measuring portion of the air to the mass flow meter; and/or the method may further comprising step of exhausting the air through an exhaust in the housing body remote from the flow connection. 
     These and other objects of the invention, as well as many of the intended advantages thereof, will become more readily apparent when reference is made to the following description, taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying figures, wherein: 
         FIG.  1    is an exemplary embodiment of the invention, showing a bottom perspective external view of the air sampling device; 
         FIG.  2    is an exemplary embodiment of the invention, showing an internal cross-sectional view of the air sampling device; 
         FIG.  3 A  is an exemplary embodiment of the invention, showing an internal cross-sectional view of the upper chamber of the air sampling device, showing air entering the device; 
         FIG.  3 B  is an exemplary embodiment of the invention, showing an internal cross-sectional view of the upper chamber of the air sampling device, showing air impinging on the media plate; 
         FIG.  3 C  is an exemplary embodiment of the invention, showing an internal cross-sectional view of the upper chamber of the air sampling device, showing air moving past the fan, the mass flow meter, and exiting the device through ventilation slots; 
         FIG.  3 D  is an exemplary embodiment of the invention, showing an internal cross-sectional view of the upper chamber of the air sampling device, showing air moving past the fan, the mass flow meter, and exiting the device through the exhaust port; 
         FIG.  4 A  is an exemplary embodiment of the invention, showing a top external perspective view of the air sampling device; 
         FIG.  4 B  is an exemplary embodiment of the invention, showing an exploded top external perspective view of the air sampling device; 
         FIG.  5    is an exploded view of the retaining assembly; 
         FIG.  6 A  is a top view of the device showing the atrium and media plate retaining assembly in an inner position; 
         FIG.  6 B  is a top view of the device showing the atrium and media plate retaining assembly in an outer position; 
         FIG.  7 A  shows the device in a vertical position and installed on a tripod; 
         FIG.  7 B  shows the device in a horizontal position and installed on a tripod; 
         FIG.  8    is a conventional sampling device; 
         FIG.  9    is another exemplary embodiment of the invention, showing an internal cross-sectional view of the air sampling device; and 
         FIG.  10    is an internal cross-sectional view of the upper chamber of the air sampling device illustrated in  FIG.  9   , showing air entering the device, impinging on the media plate, moving through the plenum and past the fan to the mass flow meter via a flow connection, and exiting the device through an exhaust. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In describing a preferred embodiment of the invention illustrated in the drawings, specific terminology will be resorted to for the sake of clarity. However, the invention is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes all technical equivalents that operate in similar manner to accomplish a similar purpose. Several preferred embodiments of the invention are described for illustrative purposes, it being understood that the invention may be embodied in other forms not specifically shown in the drawings. 
       FIGS.  1 - 2    show an exemplary embodiment of the air sampling device  100  of the invention. The device  100  is portable so it can be carried and placed at various locations within a controlled environment. As used herein, “air” refers generically to any and all gases, vapors, and particulates, and is not intended to limit the invention to particular types. The air sampling device  100  is especially useful to test for microscopic particulates in a clean room. The device  100  generally includes a sampler housing unit and a main body or housing  102 . The sampler housing unit  110  can be any suitable device, such as a cover. In the embodiment shown is a Sterilizable Microbial Atrium (SMA)  110  that covers a media plate  114  that samples particulates in an air flow and can be autoclaved or otherwise sterilized. The atrium  110  protects the media plate  114 , but allows air to flow through the atrium  110  to contact the media plate  114 . The atrium  110  can be sterilized by heat or steam, and can be autoclaved. The sampling device  100  is configured for use in a clean environment such as a clean room. 
     The housing  102  is generally cylindrical in shape and has an upper body  120  and a lower body  130 . As best shown in  FIG.  2   , the upper body  120  defines an upper interior space or upper chamber  210  that houses a blower assembly  500 , and the lower body  130  defines a lower interior space or lower chamber  250  that houses certain electronic components  300 . A wall or partition  125  separates the upper chamber  210  from the lower chamber  250 . The entire main housing  102  is a single integral member. A handle  80  ( FIG.  2   ) can be provided to carry the portable device  100 . As shown, the handle  80  can connect from the bottom of the upper housing body  120  to the bottom of the lower housing body  130 . 
     Upper and Lower Chambers  210 ,  250   
     The upper chamber  210  has a top  212  ( FIGS.  4 A,  4 B ), front ( FIGS.  4 A,  4 B ), rear ( FIG.  1   ), and opposing sides that join the front and the rear. As best shown in  FIGS.  4 A,  4 B , the top  212  of the upper chamber  210  removably couples to the atrium  110 . Returning to  FIGS.  1 ,  2   , an elongated ventilation slot  121  and a support stand  122  are positioned at the rear of the upper chamber  210 . The support stand  122  is an elongated member that receives a screw to fasten the stand  122  to the upper chamber  210 . The stand  122  can be elongated and is configured to allow the device  100  to be level when in the substantially horizontal position, and to prevent the device  100  from inadvertently rolling or tipping to one side. In addition, a fastening mechanism such as an opening can be provided on the rear of the device  100  that is configured to mate with a tripod ( FIG.  7 B ) to allow the air sampling device  100  to stand in a horizontal configuration. The fastening mechanism can be a threaded opening that threadably mates with a screw of the tripod. 
     The lower chamber  250  has a controller access panel  131 , a plurality of vertical supports  132 , and a vertical tripod receiver  133  ( FIG.  7 A ). The access panel  131  provides access to the controller and may also provide an access point for a USB slot, and or a battery. The plurality of vertical supports  132  are situated along the bottom of the air sampling device  100  such that it is stable when free-standing. The vertical supports  132  may be coated with a high-friction material like rubber or a similar synthetic polymer in order to present the air sampling device  100  from sliding along a surface. The vertical tripod receiver  133  is configured to mate with a tripod (not shown) to allow the air sampling device  100  to stand in a vertical configuration. In certain embodiments, the vertical tripod receiver  133  is threaded, such that it will screw into the tripod. Thus, the device  100  can either stand vertically on supports  132  or be threaded to a tripod by the receiver  133 . The device  100  can also stand horizontally on support stand  122 , or be threaded to a tripod by a threaded receiver. 
     Retaining Assembly  400   
     Turning to  FIG.  4 B , a receiving or retaining assembly  400  is provided at the top  212  of the upper chamber (which is also the top of the sampling device  100 ). The retaining assembly  400  is fitted to a depressed section of the top  212  having a side wall  218  and a bottom. One or more projections  113  are formed in the side wall  218 . As best shown in  FIG.  5   , the retaining assembly  400  is shown having a central securing member  430 , a top plate or disk  420 , and a bottom or bottom plate  402 , and one or more clips  410 . 
     The bottom plate  402  has one or more curved elongated grooves or bottom channels  406  that are formed as slots in the bottom plate  402 . The bottom plate  402  is fixed at the top  212  of the housing  102 . The top plate  420  has one or more curved elongated grooves or top channels  422  that are formed as slots in the top plate  420 . The top plate  420  can rotate with respect to the bottom plate  402 , which remains fixed to the housing  102 . One or more handles  426  can be provided on the top surface of the top plate  420 . The handles  426  extend upward from the top surface of the top plate  420 , so that the user can grip or push on one or more (two in the embodiment of  FIG.  5   ) of the handles  426  to rotate the top plate  420 . Each one of the top channels  422  is aligned with and overlap with a respective one of the bottom channels  406 ; however the top channels  422  are flipped in orientation with respect to the bottom channels  406 , as best shown in  FIG.  6 A , to form a Longworth chuck configuration. The channels  406 ,  422  are each a curved arc that together form a spiral-like shape. Small plastic or silicon bumpers can optionally be provided on the clip  410  that grip the agar plate  114  so that the plate  114  is compressed between the clips  410 . The compression holds the agar plate  114  in position even when the device  100  is horizontal or inverted. 
     A clip  410  is positioned in each of the respective top and bottom channels  422 ,  406 . The clip  410  has a bottom and a side formed perpendicular to the bottom to generally form an L-shape. A peg or support member  412  extends outward from the bottom of the clip  410 . The support  412  has a neck and a head that forms an inverted T-shape, with the neck extending substantially perpendicular to the bottom of the clip  410  and the head is substantially perpendicular to the neck and parallel to the bottom of the clip  410 . The neck of the support  412  extends through the top channel  422  and through the bottom channel  406 . The head of the support  412  is wide and is positioned on the bottom side of the bottom channel  406 . That locks the top plate  420  to the bottom plate  402  and also locks each clip  410  to the housing  102  and to a respective pair of bottom and top channels  406 ,  422 . It is noted, however, that the head of the support member  412  need not sit on the opposite side of the bottom plate  402  and need not lock the plates  402 ,  420 . Instead, the head of the support member  412  can just be received in the bottom channel  406  without extending through the bottom channel  406 , so that the head can slide within the bottom channel  406 . 
     As illustrated, the bottom and top channels  406 ,  422  extend slightly outward from the center so that the clip  410  moves toward and away from the center as the clip  410  slides left/right within the channels  406 ,  422 . Each channel  406 ,  422  has an innermost position (closest to the central opening  119 ) and an outermost position (furthest from the central opening  119 ). As the clips  410  move in the channels  406 ,  422 , the clips  410  continue to face in the same direction. That is, the side of the clip  410  faces the center and is substantially concentric (or parallel) to the central opening  119 . As the top plate  420  rotates, all of the clips  410  move together simultaneously within their respective channels and are equidistant from the central opening  119 . This provides a desired minimum and maximum diameter for the clips  410 . Referring to  FIG.  6 A , the clips  410  are shown at an inner position where the clips  410  are situated in the innermost position of the respective channels  406 ,  422 . In  FIG.  6 B , the clips  410  are shown at the outer position where the clips  410  are situated in the outermost position of the respective channels  406 ,  422 . The clips  410  are moved between the inner and outer positions by rotating the top plate  420  with respect to the bottom plate  402 . In one embodiment, the inner position can provide a diameter of 85 mm, and the outer position can provide a diameter of about 100 mm, which are common sizes for media plates. 
     The securing member  430  has a neck  432 , wide head  434 , and is ring-shaped to form a central opening  436 . The bottom plate  402  and top plate  420  each have a respective central opening  404 ,  424 . The plates  402 ,  420  are circular, and form a donut-shape with the central openings  404 ,  424 . The bottom central opening  404  can be internally threaded. The neck  432  of the securing member  430  can be externally threaded to mate with the threaded central bottom opening  404 . 
     The neck  432  extends through the top plate central opening  424  and threadably engages the bottom plate central opening  404 , thereby locking the top plate  420  to the bottom plate  402 , but allowing the top plate  420  to rotate with respect to the bottom plate  402 . However, the securing member  430  sufficiently compresses the head of the support member  412  between the top plate  420  and the bottom plate  402  to provide enough friction so that the clips  410  stay in the position set by the user and grip the agar plate  114  without inadvertently sliding in the channels  406 ,  422  and thereby being locked in position. The securing member  430  can be curved to be ergonomic and tapered inward to facilitate the flow of air into the central opening  119  that extends through the securing member central opening  436 , top plate central opening  424 , and bottom plate central opening  404 . 
     As further shown in  FIG.  4 B , a test or sampling device such as a Petri dish or Agar media plate  114  is provided having a test medium contained therein. The media plate  114  is placed on the bottom portion of the clips  410 . The clips  410  hold the media plate  114  in place. The clips  410  slide in/out in the grooves  406 ,  422  so that the dish  114  snugly fits between the clips  410  and does not inadvertently come free from the clips  410 , such as when the device  100  is turned horizontally. The media plate  114  can, for example, contain agar media that is designed to capture particulates in the air entering the device  100 . The captured particulates can then be analyzed. 
     Thus, the adjustable clips  410  are configured to slide inwardly and outwardly along the diameter of the base of the atrium  110  to accommodate agar media plates  114  of varying diameters. Once the diameter is adjusted to match that of the agar media plate  114 , the pegs  414  of the adjustable clips  410  can be moved from an unlocked position to a locked position, securing the agar media plate  114 . The pegs  414  are positioned such that they grab the outer edge of the agar media plate  114 . The pegs  414  each have a slight angle which, when the pegs  414  are positioned at roughly the diameter of the plate, causes an inward force against the walls of the agar media plate  114 , securing it. Thus, the media plate  114  is press fit into the clips and is retained by the pegs  414 . 
     Atrium  110   
     Referring to  FIGS.  2 ,  4 A,  4 B , the atrium  110  is removably coupled to the top  212  of the sampling device  100  and is in direct air flow communication with the upper chamber  210 . The atrium  110  has a cover plate  111  with a flat top and downwardly extending sides that are wider than the clips  410 . A plurality of openings  112  are formed in the top of the cover plate  111 . Referring to  FIG.  4 B , one or more locking slots or channels  112  are formed in the side of the cover plate  111 . Each of the locking channels  112  is aligned with a respective projection  113  on the side wall  218  of the receiving portion  216 . The locking channel  112  has a vertical portion and a horizontal portion. 
     To attach the atrium  110  to the housing  102 , the user places the atrium  110  over the top of the media plate  114  so that the projection  113  enters the vertical portion of the locking channel  112 . Once the projection is fully received in the vertical portion of the locking channel  112 , the user can rotate the atrium  110  so that the projection  113  enters the horizontal portion of the locking channel  112 , thereby removably locking the atrium  110  to the main housing  102  ( FIG.  4 A ). The entire device  100  can be placed horizontally and the atrium  110  will continue to be fixed to the top  212  of the main housing  102 . The user can remove the atrium  110  by twisting the atrium  110  and pulling outward, so that the projection slides out along the horizontal portion and then pulls out from the vertical portion of the locking channel  112 . 
     Blower Assembly  500   
     Referring to  FIG.  2   , a blower assembly  500  is provided in the upper chamber  210  of the air sampling device  100 . The blower assembly  500  has a blower housing  502  and a fan  504 . The blower housing  502  is a plenum that conveys air. The plenum  502  has at least one wall and in the embodiment of  FIG.  2    is cylindrical in the form of a tube with two open ends. The blower housing  502  can be a single integral device, or multiple separate discrete housings that are coupled together by lips  503 ,  505  extending outward at the end of each respective housing. Thus the top lip  503  of the first housing can be coupled to the top  112  of the housing  102 , and the bottom lip  503  of the first housing can be coupled to the top lip  505  of the second housing, as shown. The bottom lip  505  of the second housing can be coupled to the mass flow detector or detector adapter. A gasket can optionally be provided between the lips  503 ,  505  and the respective connections to provide an airtight seal therebetween so air does not leak out of the plenum  502 . Thus, the plenum  502  has a top end and a bottom end opposite the top end. The top end of the plenum  502  is coupled to the top of the housing  102  about the central opening  119 , so that the plenum  502  is in air flow communication with the retaining assembly  400  and atrium  110 . The plenum  502  is substantially the same size as the central opening  119 , and perhaps slightly larger. Thus, the fan  504  to pull air directly through the atrium  110  and retaining assembly  400  via the central opening  119 . 
     A fan  504  is located inside the plenum  502 . The fan  504  has a center support rod and fan blades  506 . The center rod has a longitudinal axis that extends substantially parallel to the longitudinal axis of the sampling device  100 . The fan blades  506  extend outward from the center rod and are configured to draw air down (in the embodiment of  FIG.  2   , when the sampling device  100  is standing vertical or upright) through the plenum  502 . The upper chamber  210  is sized and shaped to accommodate and match standard sized and shaped agar media plates  114 , as well as the electronic components in the bottom chamber  250 . 
     Thus, the blower assembly  500  is elongated and has a longitudinal axis that is parallel to the longitudinal axis of the sampling device  100 . Accordingly, the longitudinal axis of the blower assembly  500  (including the fan  504  and plenum  502 ) is vertical when the sampling device  100  is vertical ( FIG.  7 A ), and is horizontal when the sampling  100  device is horizontal ( FIG.  7 B ). The plenum  502  and fan  504  can be smaller than the media plate  114  to create an air flow through the atrium  111  that provides reliable test results for the media plate  114 . As shown, the plenum  502  and fan  504  can be about half the size of the media plate  114 , and is centrally located with respect to the media plate  114 . 
     Referring to  FIGS.  9  and  10   , an alternative blower assembly  500 ′ is shown according to another exemplary embodiment of the invention. The blower assembly  500 ′ of this embodiment is similar to the blower assembly  500  of the above embodiment, except that a flow connection  900  is added to connect the blower assembly  500 ′ to a mass flow meter  600 ′ such that the mass flow meter  600 ′ is in flow communication with blower assembly  500 ′ via flow connection  900 . The blower assembly  500 ′ has a plenum  502 ′ and a blower or fan  504 ′ in association with plenum  502 ′. Like plenum  502  of the above embodiment, plenum  502 ′ of this embodiment can be a single integral device or multiple separate discrete housings that are coupled together. The plenum  502 ′ may have a top end  503 ′, a bottom end  505 ′, and a longitudinal side or length  507 ′ defined therebetween. The longitudinal length  507 ′ is preferably generally parallel to the longitudinal axis of the sampling device  100 . As such, the longitudinal length  507 ′ of plenum  502 ′ may be vertical when the sampling device  100  is vertical or horizontal when the sampling  100  device is horizontal. The top end  503 ′, which may have a lip, can be coupled to the top  112  of the housing  102  and the bottom end  505 ′, which may have a lip, can be coupled to the mass flow meter via the flow connection  900 . Plenum  502 ′ is configured to receive air from the retaining assembly  400  and atrium  110  through its top end  503 ′ and generally along its longitudinal length  507 ′. Fan  504 ′ may operate inside of plenum  502 ′ to pull air directly through the atrium  110  and retaining assembly  400  via the central opening  119 . 
     Flow connection  900  is preferably a conduit arranged between plenum  502 ′ and the mass flow meter  600 ′. The flow connection  900  has a central opening and is airtight, and for example can be a flexible plastic tube or plenum. The flow connection  900  can have any shape such as circular or square, though preferably has a circular cross-section and a circular central opening. Flow connection  900  is configured to divert a portion or percentage of the air flowing through the blower assembly  500 ′, namely a measuring portion of the air, to be measured by the mass flow meter  600 ′. The measuring portion of the air is proportional to the air flowing through the blower assembly  500 ′. Total flow through the plenum is proportional to the ratio of the cross-sectional area between flow connection  900  and the cross-sectional area of plenum end  505 , i.e. the cross-sectional area of the plenum  502  at the end of the flow connection  900  or at any location where the flow connection  900  is connected with or positioned with respect to the plenum  502 . Output from the mass flow meter is a voltage that is proportional to the flow through the meter, that voltage is electronically converted into a digital value and scaled to the desired units for display. 
     Flow connection  900  generally has a receiving end  902  adapted to couple with the bottom end  505 ′ of plenum  502 ′, an opposite exit end  904  adapted to couple with the mass flow meter  600 ′, and a conduit body  906  therebetween. The receiving end  902  may be mounted about or extend through a hole in the plenum&#39;s bottom end  505 ′, for example, to connect the flow connection  900  thereto such that the plenum  502 ′ is in fluid (i.e., flow) communication with conduit body  906 . The conduit body  906  may be shaped, e.g. a generally U-shape, such that the receiving and exit ends  902  and  904  are generally at the same height in the housing body, that is the ends are generally aligned with respect to an axis transverse to the longitudinal length  507 ′ of plenum  502 ′. Exit end  904  may also be mounted to the bottom end  505 ′ of plenum  502 ′ such that it is adjacent plenum  502 ′ and remote from, i.e. not near or adjacent to, the exhaust  121  in the housing. In a preferred embodiment, at least one portion  908  of the conduit body  906  extends below the plenum&#39;s bottom end  505 ′ in a direction generally parallel to the longitudinal length  507 ′ of the plenum  502 ′. Alternatively, the exit end  904  may be positioned near exhaust  121 . 
     The flow connection  900  is elongated and has a longitudinal axis. In one non-limiting embodiment of the invention, the longitudinal axis at the receiving end  902  can be substantially parallel to the longitudinal axis of the plenum  502 ′. In this manner, and as best shown in  FIG.  10   , at least a portion of the air flow exiting the plenum  502 ′ at the bottom end  505 ′ continues straight into the central opening of the flow connection  900  without any obstruction, and the remaining air flow exiting the plenum  502 ′ continues out through the exhaust  121  or port, as before. That enables the flow connection  900  to get a true and reliable reading of the flow rate through the plenum  502 ′. The flow connection  900  can have a bend, if needed to fit the mass flow meter  600 ′ in the interior space of the upper chamber  210 . Though the flow connection  900  is shown as having a U-shape, any suitable shape can be provided, including that the body  906  be straight without any bend. In addition, in one embodiment, the flow connection  900  can be positioned at the outer perimeter of the plenum  502 ′ just at the lower edge of the bottom end  505 ′ of the plenum  502 ′ (i.e., just inside the side wall of the plenum  502 ′). However, the flow connection  900  can be positioned at any suitable location at the opening of the plenum  502 ′, including for example inside the plenum  502 ′ or inset closer toward the center of the plenum  502 ′. In addition, though only a single flow connection  900  and mass flow meter  600 ′ is shown, more than one flow connection  900  and/or mass flow meter  600 ′ can be provided. 
     Mass Flow Meter  600   
     A mass flow meter  600  is also located in the upper chamber  210 , and is positioned immediately and directly below the blower assembly  500 . The mass flow meter has an input  602  at a top end and an output  604  at a bottom end. The input  602  is coupled to the bottom open end of the plenum  502  and is in unobstructed air communication with the plenum  502 . Thus, the mass flow meter  600  directly receives the air flow passing through the plenum  502 . If the bottom end of the plenum  502  is larger than the input  602  of the mass flow meter  600 , an adapter  603  can optionally be provided to maintain an airtight seal between the bottom of the plenum  502  and the input  602  of the mass flow meter  600 , as shown. 
     The mass flow meter  600  measures the rate of air flow coming into the sampling device  100  through the atrium  110 , striking the media plate  114 , through the plenum  502 , and into the input  602 . Once air exits the output  604  of the mass flow meter  600 , it enters the upper chamber  210  and exits via the vent  121  in the housing  102 . 
     As shown, the upper chamber  210  contains an operator display and/or control panel  302 , the blower assembly  500  and the mass flow meter  600 . The control panel  302  is an electronic touch display that enables the user to control operation of the sampling device  100 . The control panel  302  is affixed to the housing  102  and can optionally extend into the upper chamber  210 , for example. However, the control panel  302  forms an air and/or liquid tight seal with the housing  102  so that air does not leak out of the upper chamber  210 . 
     Referring to  FIGS.  9  and  10   , an alternative mass flow meter  600 ′ in accordance with another exemplary embodiment of the invention is shown. Mass flow meter  600 ′ is coupled to the exit end  904  of flow connection  900  and may be located anywhere in upper chamber  210 . In a preferred embodiment, mass flow meter  600 ′ is positioned near or adjacent to plenum  502 ′ and remote from, i.e. not near or adjacent to, the exhaust  121  of the device. Alternatively, mass flow meter  600 ′ may be positioned near exhaust  121 . Mass flow meter  600 ′ has an input  602 ′ and an output  604 ′. The input  602 ′ is configured to couple to exit end  904  of flow connection  900 , thereby providing flow communication with plenum  502 ′. Thus, air flows through plenum  502 ′, then through flow connection  900 , and into the input  602 ′ of mass flow meter  600 ′. 
     Similar to mass flow meter  600  of the above embodiment, mass flow meter  600 ′ measures the rate of air flow. In this embodiment, mass flow meter  600 ′ measures the rate of flow of the measured portion of the air coming through flow connection  900 . Because the measured portion of the air is proportional to the air coming through the device, i.e. into the atrium  110 , striking the media plate  114 , through the plenum  502 ′, the detected rate of flow of the measuring portion of the air by mass flow meter  600 ′ represents the rate of flow of the air coming through the sampling device  100 . In one non-limiting embodiment of the invention, output from the mass flow meter is a voltage that is proportional to the flow through the meter. That voltage is electronically converted into a digital value and scaled to the desired units for display. Once the measuring portion of the air exits the output  604 ′ of the mass flow meter  600 ′, it enters the upper chamber  210  and exits via the exhaust  121  in the housing  102 . 
     Electronic Component Assembly  300   
     All other electronic components  300  (besides the control panel  302 , blower assembly  500  and mass flow meter  600 ) are contained in the lower chamber  250 . That provides stability to the sampling device  100  and reduces the width/diameter of the sampling device  100 . The electronic component assembly  300  can include, for example, a controller  304 , power supply (batteries), and a motor  306 . In certain embodiments, the controller may be a computer or processing device such as a processor or ASIC. The controller  304  operates the fan  504 , mass flow meter  600 , and control panel  302 . It receives  304  operator control signals from the control panel  302 , such as to start and stop test, set test parameters (time, flow rate, etc.). The controller  304  also displays information about operation of the sampling device  100  on the control panel  302 , such as flow rate, testing time, and remaining test time. The controller  304  can also communicate with remote devices, such as controllers  304  in other sampling device  100  or a personal computer, network or smart phone, either by hard wire or wirelessly. 
     Thus, the controller  304  runs the fan  504  and the mass flow meter  600  of the air sampling device  100 . When the sampling process is engaged, the system attempts to generate the desired flow rate. The mass flow meter  600  continually reports the instantaneous flow rate through the system to the controller  304 . The controller  304  evaluates whether the measured flow rate is equal to the desired flow rate (usually 1 cfm). The difference between the desired flow rate and the measured flow rate is known as the error. If the desired flow rate is greater than the measured flow rate, the controller  304  will increase the frequency of fan  504  revolutions to generate a higher flow rate. If the desired flow rate is less than the measured flow rate, the controller  304  will decrease the frequency of the fan  504  revolutions to generate a smaller flow rate. This process may be repeated continuously (many times per second or nonstop) or at regular intervals. The process of evaluating a system&#39;s output and modifying the systems input provides a closed-loop control. A proportional-integral-differential (“PID”) control algorithm is used by the controller  304  to minimize and maintain a low system error. The air sampling device  100  preferably uses this control method to adjust the fan speed based on the instantaneous flow rate. Accordingly, controller  304  controls the fan  504  speed in real time without delay or manual interaction, based on the real time feedback provided by the mass flow meter  600 . 
     In one exemplary embodiment, the controller  304  can be networked and connected to the Internet via TCP/IP networking using IEEE 802.3 (wired), IEEE 802.11 (wireless), and IEEE 802.15.4 (wireless for Bluetooth) physical and data link standards. In alternative embodiments, the controller  304  may receive and send commands remotely through the network. Through the network, the air sampling device  100  can be monitored and controlled remotely using networked devices and applications, such as a processing device (smart phone, computer, etc.). The air sampling device  100  can also export event history to a removable USB flash drive. The flash drive and USB connection terminal can be accessed through a controller access panel  131  ( FIG.  1   ) that is flat and supports the device  100  in a horizontal position. Event history includes sampling events, calibration events, and administrative events. In one embodiment, the device  100  can be integrated with the networks and central processing device to facilitate monitoring and control from a central location, such as those shown in U.S. Pat. Nos. 9,285,792, 9,063,040, 9,046,453, and U.S. Patent Publication No. 2016/0061796. The content of those patents and applications is hereby incorporated by reference. 
     Ventilation Slots  121  and Port Adapter  650   
     Referring to  FIG.  1   , an elongated ventilation slot  121  is located at bottom rear of the upper housing body  120 . The ventilation slot  121  can have vertical members that are integrally formed with the housing  102  to create a plurality of slots and provide safety. An exhaust port adapter  650  can optionally be provided that mates with the ventilation slots  121 . The adapter  650  has a base  652  and a nozzle  654 . The base  652  has the same shape as the ventilation slot  121 . The base  652  covers and couples with the slot  121  in an airtight manner to prevent air from leaking out of the housing  102  except through the nozzle  654 . The nozzle  654  projects outward from the base  652  and has a center opening that extends through the nozzle  654  and base  652 . 
     A tube can be attached to the nozzle  654  to transport exhausted air to a remote location outside of the clean environment. Accordingly, air from the upper chamber  210  is exhausted through the nozzle  654  and into the tube. 
     The exhaust port adapter  650  removably mates with the ventilation slots  121  through an exhaust mating mechanism  656 . The exhaust mating mechanism  656  can male members (such as spring-biased arms or the like) which slide into and couple with the female ventilation slots  121  and grip the vertical supports. The exhaust nozzle  654  is exemplarily shown as a substantially cylindrical output nozzle, but may be of any shape that allows for the attachment of tubing. In certain embodiments, the exhaust nozzle  654  may allow for the use of clamps to secure tubing and create an airtight seal. In other embodiments, the outside of the exhaust nozzle  654  may be ribbed and tapered to allow for tubing to form an airtight seal by being pushed against it. 
     In yet another alternative embodiment of the invention, the ventilation slot  121  can be an opening in the housing  102  and a separate grill can be provided that is fastened into the slot  121  (such as by a fastening mechanism or friction fit) and can be removed and replaced with an exhaust adapter  650 . 
     Accordingly, the ventilation opening or slot  121  and/or the exhaust port adapter  650  allow for air passing through the air sampling device  100  to exit to the external environment. The air enters through openings in the atrium  110  at the top of the upper body  120 , and exits through the ventilation slot  121  at the rear of the upper body  120 . The ventilation slot  121  can be positioned at the bottom part at the rear of the upper body  120 , to provide a direct and continuous air flow through the sampling device  100 . 
     Operation—Air Flow 
     The operation of the air sampling device  100  will now be discussed with respect to  FIGS.  2 ,  3 A- 3 D, and  10   . Operation begins when an operator sets a sampling test parameter and presses start, or when a previously set test is programmed to begin (such as every 4 hours). At that point, the controller  304  starts the fan  504  or  504 ′ to operate. The fan  504  or  504 ′ pulls air into the sampling device  100  via the atrium openings  112 , as shown by the arrows showing the air flow  10  ( FIGS.  3 A and  10   ), and draws air across the agar media plate  114 , air flow arrows  12  ( FIGS.  3 B and  10   ). The air strikes the media plate  114  and passes around the plate  114 , underneath the plate  114  (as shown in  FIG.  2   , there is a space between the bottom of the media plate  114  and the bottom  402  and also between the bottom of the media plate  114  and the top of the securing member  430 ) and exits through the central opening  119  in the retaining assembly  400 , as shown by air flow arrows  14  ( FIGS.  3 C and  10   ). 
     It is noted that the speed of the air entering the system through each opening  112  is a function of the speed of the fan  504  or  504 ′ as well as the diameter and number of openings  112  in the atrium  110 . As air enters the region below the openings  112  (air flow  12 ,  FIGS.  3 B and  10   ), it is redirected toward the nearest vacuum source, the central opening  119 . The initial direction of air flow  10  ( FIGS.  3 A and  10   ), and the new direction of the air flow  12  ( FIGS.  3 B and  10   ), are nearly perpendicular. When the air is redirected, many fast-moving particles within the air cannot be redirected so abruptly due to their inertia. These particles roughly continue their initial direction and impinge the agar media plate  114  where the individual particles remain. The focus of this process is to accumulate these particles within the agar, where they can be analyzed at a later time. The redirected air is drawn laterally outward across the agar-side of the agar media plate  114 , over its edges, down the outside of its exterior walls, and laterally inward across the bottom-side of the plate  114  until it is drawn through the central opening  119 . 
     Once the air flow passes through the atrium  110  (air flow  10 ) and retaining assembly  400  through the central opening  119  (air flow  14 ), it enters into the plenum  502  or  502 ′ situated inside the upper chamber  210  of the air sampling device  100 , as shown by the arrows for air flow  16  ( FIGS.  3 C and  10   ). The air enters directly from the central opening  119  into the open top end of the plenum  502  or  502 ′ (air flow  14 ). The fan  504  or  504 ′ pushes the air through the plenum  502  or  502 ′ (air flow  16 ) until it exits the open bottom end of the plenum  502  or  502 ′ (air flow  18 ). The air continues through the adapter  603  (if one is used) to the input  602  of the mass flow meter  600 . Alternatively, the measuring portion of the air is diverted through flow connection  900  to the input  602 ′ of the mass flow meter  600 ′. The mass flow meter  600  or  600 ′ constantly measures the rate of the air flow  18  and provides a measured air flow rate signal with the detected air flow rate to the controller  304 . The controller  304  will continuously read the measurement signal and adjust the speed of the fan  504  or  504 ′ to account for any difference between the measured air flow rate and a desired air flow rate. 
     The air flow continues through the mass flow meter  600  or  600 ′ and exits through the output  604  or  604 ′, as shown by the arrows for air flow. As shown in  FIGS.  3 C and  10   , the air flow exits the mass flow meter  600  or  600 ′ into the upper chamber  210 . As the upper chamber  210  becomes pressurized (relative to ambient pressure), air is exhausted through the exhaust, e.g. ventilation slot  121  to the exterior of the device  100 . The optional partition wall  125  prevents air from entering the lower chamber  250  so that the lower chamber  250  and electronics  300  do not interfere with the air flow. Since the motor  306  is part of the fan assembly  504 , it does not need to be cooled. The exhausted air exits the air sampling device  100  substantially parallel to the orientation at which it entered in order to maintain laminar flow within the environment. It is exhausted outside of the sampling device  100  and the housing  102  through the ventilation slot  121  at the rear of the upper chamber  210 . In an alternative embodiment, a plenum or tube can connect the output  604  or  604 ′ of the mass flow meter  600  or  600 ′ to the ventilation slot  121 . 
     As shown in the alternative exemplary embodiment of  FIG.  3 D , an exhaust plug can replace or be attached to the ventilation slot  121  so that the air flow  20  is exhausted through the port adapter  650 . A tube can be connected to the nozzle  654  of the port adapter  650  to transport the air to a remote location outside the clean environment, where it is finally disposed or exhausted. Thus, air passes through the ventilation slot  121  and/or the port adapter  650  and is redirected into the attached tubing. 
     It is noted that the sampling device  100  and its various components, are shown to have a generally cylindrical shape. For instance, the atrium  110 , retaining assembly  400 , top plate  420 , bottom plate  402 , media plate  114 , securing member  430 , and blower assembly  212  are all cylindrical. It will be appreciated that the invention does not need to be configured to be cylindrical or circular, and that other shapes can be provided within the spirit and scope of the invention. 
     The description uses several geometric or relational terms, such as circular, rounded, tapered, parallel, perpendicular, concentric, arc, and flat. In addition, the description uses several directional or positioning terms and the like, such as top, bottom, left, right, up, down, inner, and outer. Those terms are merely for convenience to facilitate the description based on the embodiments shown in the figures. Those terms are not intended to limit the invention. Thus, it should be recognized that the invention can be described in other ways without those geometric, relational, directional or positioning terms. In addition, the geometric or relational terms may not be exact. For instance, walls may not be exactly perpendicular or parallel to one another but still be considered to be substantially perpendicular or parallel because of, for example, roughness of surfaces, tolerances allowed in manufacturing, etc. And, other suitable geometries and relationships can be provided without departing from the spirit and scope of the invention. 
     In addition, the sampling device  100  includes operation by a one or more processing devices, such as the controller  304 . It is noted that the processing device can be any suitable device, such as a processor, microprocessor, PC, tablet, smartphone, or the like. The processing devices can be used in combination with other suitable components, such as a display device (monitor, LED screen, digital screen, etc.), memory or storage device, input device (touchscreen, keyboard, pointing device such as a mouse), wireless module (for RF, Bluetooth, infrared, WiFi, Zigbee, etc.). Information operated on or output by the processing device may be stored on a hard drive, flash drive, on a CD ROM disk or on any other appropriate data storage device, which can be located at or in communication with the processing device. The entire process is conducted automatically by the processing device, and without any manual interaction. Accordingly, unless indicated otherwise the process can occur substantially in real time without any delays or manual action. 
     Within this specification, the terms “substantially” and “about” mean plus or minus 20%, more preferably plus or minus 10%, even more preferably plus or minus 5%, most preferably plus or minus 2%. 
     Within this specification embodiments have been described in a way which enables a clear and concise specification to be written, but it is intended and will be appreciated that embodiments may be variously combined or separated without departing from spirit and scope of the invention. For example, it will be appreciated that all preferred features described herein are applicable to all aspects of the invention described herein. 
     The air sampling device  100  is especially useful for use in a controlled environment. It can be made of materials that are suitable for use in a controlled environment. However, the sampling device  100  can be utilized in other environments. 
     The foregoing description and drawings should be considered as illustrative only of the principles of the invention. The invention may be configured in a variety of shapes and sizes and is not intended to be limited by the preferred embodiment. Numerous applications of the invention will readily occur to those skilled in the art. Therefore, it is not desired to limit the invention to the specific examples disclosed or the exact construction and operation shown and described. Rather, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.