Abstract:
A fume hood is provided that can reduce emissions. The fume hood has a work chamber with a front side and an exhaust opening. The front side has an upper shield and a sash below the upper shield. The sash comprises at least one sash shield, wherein the at least one sash shield at least partially defines at least one sash opening in the front side to allow access to the work chamber.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The subject matter disclosed herein relates to fume hoods, and more particularly to reduced-emission fume hoods. 
         [0002]    A fume hood is a type of local ventilation device that is designed to limit the user&#39;s exposure to hazardous or noxious fumes, vapors or dusts. Fume hoods are commonly used in laboratories where hazardous or noxious chemicals are released during testing, research, development, or teaching. Fume hoods are also used in industrial applications or other activities where hazardous or noxious vapors, gases, or dusts are generated or released. 
         [0003]    A fume hood can enclose five sides of a work chamber, the bottom of the work chamber having a work surface, which is located at a work height for the user, whether sitting, standing, or otherwise. The front side of the work chamber has an opening, called a sash. The sash is open to the room occupied by the fume hood and the user so that the user can access the work chamber enclosed by the fume hood. Some sashes can be closed when the fume hood is not in use. 
         [0004]    The top side or one of the lateral sides near the top side of the work chamber, has a vent to expel contaminated air containing the hazardous or noxious fumes, vapors, or dusts. The contaminated air can be expelled, for example, through a duct to the outside of a building in which the fume hood is contained. While air is expelled through the vent, fresh air is drawn into the fume hood through the sash. 
         [0005]    The proper flow of fresh air into the fume hood through the sash and/or other inlet vents, and of contaminated air out of the fume hood from the work chamber through the vent, is essential to the proper functioning of the fume hood in expelling dangerous air and in protecting the user and/or other individuals in the room from inhaling contaminants. Fume hoods are intended to reduce, minimize, or prevent contaminated air from flowing or leaking into the room where a user or other individuals can be exposed. To reduce or prevent leaking through the sash, safety regulations and industry standards require a minimum velocity of air along the surface of the sash. This velocity is referred to as a face velocity. If the standard of ASHRAE 110 “Method of Testing Performance of Laboratory Fume Hoods” and NFPA 45 “Standard on fire protection for laboratories using chemicals” 2004 edition are met, then a face velocity between 80 ft/min and 120 ft/min (≈0.4 m/s to ≈0.6 m/s) can contain gases in the fume hood. 
         [0006]    In order to maintain a proper face velocity, a significant amount of air is circulated into and through the fume hood. In one example, a five foot long fume hood with a 14 inch by 56 inch sash (0.3556 meters by 1.4224 meters), and a face velocity of about 120 ft/min (≈0.6 m/s) at the sash, nominally exhausts about 800 cubic feet of air per minute (CFM) (22.64 cubic meters per minute) from the work surface and another 80 CFM (2.264 cubic meters per minute) from a connected storage cabinet. Large quantities of energy and money are required to run fans that move this air through the fume hood. Furthermore, the air that is circulated into the fume hood from the room or laboratory is conditioned to control humidity, temperature, and/or composition (e.g. cleanliness) as the air conditions are important in many laboratory environments or other environments where fume hoods are used. Often, many fume hoods are in use simultaneously in a room or laboratory, which multiplies the amount of conditioned air moved through the fume hood and exhausted from the room and/or building. Since conditioning air costs a significant amount of energy and money, moving less air through the fume hood while maintaining the face velocity can provide significant savings. 
         [0007]    One method that attempts to reduce the expense associated with moving conditioned air through the fume hood transfers air from outside the building through ducts, and outputs the air directly in front of the fume hood, where it can be drawn into the fume hood. This method increases the costs in ductwork, and delivers unconditioned air that can be too hot, too cold, or too humid, which is uncomfortable to a user and unacceptable for many procedures in the fume hood. 
         [0008]    Another method uses a variable air volume (VAV) system, which reduces the volume of the air exhausted as the fume hood sash is closed. The VAV system is often enhanced by an automatic sash closing device, which will close the fume hood sash when the user leaves the fume hood face. This fume hood attempts to minimize the exhaust volume whenever no one is actually working with hands in the fume hood through the sash. However, it does not minimize or reduce the exhaust during use. 
         [0009]    It would be advantageous to provide a fume hood that reduces the expenditure of energy during active use, without reducing the face velocity and without using unconditioned air. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0010]    In one embodiment, a fume hood comprises a work chamber with a front side and an exhaust opening. The front side has an upper shield and a sash below the upper shield. The sash comprises at least one sash shield, the at least one sash shield being slidable and at least partially defining at least one adjustable sash opening in the front side to allow access to the work chamber. 
         [0011]    In another embodiment, a fume hood comprises a work chamber partially enclosed by a bottom work surface, a first side panel, a second side panel, a top side panel, a back side panel, and a front side. The fume hood also comprises an exhaust opening in one of the first side panel, the second side panel, the top side panel, and the back side panel. The front side comprises an upper shield and a sash below the upper shield. The sash further comprises a first end sash shield, a second end sash shield, and at least one center sash shield between the first end sash shield and the second end sash shield. The first end sash shield and the at least one center sash shield at least partially define a first opening in the front side to allow manual access to the work chamber. The second end sash shield and the at least one center sash shield at least partially define a second sash opening in the front side to allow manual access to the work chamber. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    So that the manner in which the features of the invention can be understood, a detailed description of the invention may be had by reference to certain embodiments, some of which are illustrated in the accompanying drawings. It is to be noted, however, that the drawings illustrate only certain embodiments of this invention and are therefore not to be considered limiting of its scope, for the scope of the invention encompasses other equally effective embodiments. The drawings are not necessarily to scale, emphasis generally being placed upon illustrating the features of certain embodiments of invention. Thus, for further understanding of the invention, reference can be made to the following detailed description, read in connection with the drawings in which: 
           [0013]      FIG. 1  is a perspective view of a fume hood in one exemplary embodiment of the invention. 
           [0014]      FIG. 2  is a perspective view of a fume hood in another exemplary embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]      FIG. 1  is a perspective view of a fume hood  100  in one exemplary embodiment of the invention. The fume hood  100  can comprise a work chamber  102  defined by a first side panel  104 , a second side panel  106 , a top side panel  108 , a back side panel  110 , a bottom side panel  112 , and a front side  114 . The bottom side panel  112  can be used as, or can have, a work surface. The fume hood  100  can be supported by a base  120 . The base  120  can contain cabinets  122  for storage of solvents and/or other materials used in the hood&#39;s work chamber  102 . The cabinets  122  can be fluidly connected to the work chamber  102 , meaning gases and other fluids can flow between the cabinets  122  and the work chamber  102 . The cabinets  122  can have cabinet doors  124  with vents  126 . The fume hood  100  can be sized variously. Typical lengths of the fume hood  100  between the first side panel  104  and the second side panel  106  can be between 3 feet and 8 feet (0.9144 meters and 2.4484 meters) in length (e.g. distance between the first side panel  104  and the second side panel  106 ), but the fume hood  100  can also be shorter or longer. Typical depths of the fume hood  100  between the front side  114  and the back side panel  110  can be between 30 inches and 48 inches (0.762 meters and 1.2192 meters), although the fume hood can have smaller or larger depths. 
         [0016]    The fume hood  100  can comprise features to enhance the work chamber  102  and/or operator experience. For example, the fume hood can comprise lights  130 , light switches  132 , an exhaust monitor  134 , a sink  136 , and a faucet  138 . Temperature sensors, humidity sensors, and other gauges and sensors can also be used. Many other options can be incorporated as well. 
         [0017]    An exhaust opening  140  can be positioned in one of the panels  104 ,  106 ,  108 ,  110 . The exhaust opening  140  can connect the work chamber  102  to exhaust ducts (not shown), which allow air to flow from the work chamber  102  and cabinets  122  and be expelled or exhausted to a desired location, such as an area outside of a building in which the fume hood  100  is located. Air blowers (not shown) can provide the motive force to move the air in the proper direction out of the work chamber  102  through the exhaust opening  140 . 
         [0018]    The front side  114  can connect to the first side panel  104 , the second side panel  106 , the top side panel  108 , and the bottom side panel  112 . The front side  114  can comprise an upper safety shield  150  and a sash  152 . The upper safety shield  150  can be perpendicular to the top side panel  108 , or as shown in  FIG. 1 , the upper safety shield  150  can be angled nonperpendicularly with the top side panel  108 , such as at an angle between 30 degrees and 60 degrees. A nonperpendicularly angled upper safety shield  150  can enable an operator facing the work chamber  102  to lean the operator&#39;s upper body and/or head toward, and even over the work chamber  102 . Allowing the operator to lean forward can enable better access (e.g. longer reach into the work chamber  102 ) and/or better viewing of the work chamber  102 . 
         [0019]    The upper safety shield  150  can be substantially flat or planar, as shown in  FIG. 1 . Alternatively, as seen in  FIG. 2 , which is a perspective view of a fume hood in one exemplary embodiment of the invention, the upper safety shield  150  can curve from the sash  152  to the top side panel  108 . The curved shape of the upper safety shield  150  can be ergonomic, permitting an operator to lean forward toward the work chamber  102  and permitting easier reach into the work chamber  102 . Also, the upper safety shield  150  can extend parallel, or close to parallel (e.g. horizontally or close to horizontally) with the top side panel, which can enable an operator better viewing of the work area  102  from the operator&#39;s non-leaning position, or as the operator leans forward over the work chamber  102 . 
         [0020]    The upper safety shield  150  can be fixed in place and can be unmovable during normal operation, or the upper safety shield  150  can be configured to be moveable during normal operation. For example, the upper safety shield  150  can be hinged at the top edge near the top side panel  108 , so that the upper safety shield  150  can be opened outward and upward from the bottom edge near the sash  152 . The upper safety shield  150  can also be hinged on any of the other three edges of the upper safety shield  150 . A moveable (e.g. openable) upper safety shield  150  can allow the upper safety shield  150  to be closed a maximal amount of time, and/or while harmful fluids are in the work chamber  102 , and then opened to allow an operator easier access for tasks, such as cleaning or inserting or removing larger items that cannot fit through the sash  152 . A movable upper safety shield  150  can allow greater access to the work area  102  when it is not necessary to have the upper safety shield  150  closed to maintain adequate air flow and to protect an operator from dangerous solvent splashes or other hazards. 
         [0021]    The sash  152  can comprise two sash openings  154 , a first end lower safety shield  156 , a second end lower safety shield  158 , and a center lower safety shield  160 . The sash  152  can be bounded above by the upper safety shield  150 , on the sides by the first side panel  104  and the second side panel  106 , and below by the bottom side panel  112 , the base  120  and/or the cabinets  122 . The size of the sash  152  can vary, depending at least in part on the size of the fume hood  100 . For example, the length of the sash  152  can be up to the full length of the fume hood  100 . In one embodiment, the sash height is approximately 10 inches (0.254 meters). 
         [0022]    The first end lower safety shield  156  and the second end lower safety shield  158  can be fixed in place, while the center lower safety shield  160  can be movable. In one embodiment, the center lower safety shield  160  can slidably rest on a lower rail  163 , with the upper edge of the center lower safety shield  160  slidably engaging the upper safety shield  150  or an upper rail  164  that engages the upper safety shield  150 . Each lower safety shield  156 ,  158 ,  160  can be a panel of clear, solid material (e.g. glass or plexiglass). The sash openings  154 , which can be adjusted by the movement of the center lower safety shield  160 , are defined by the center lower safety shield  160  and each of the end lower safety shields  156 ,  158 . 
         [0023]    One sash opening  154  can be enlarged while the other sash opening  154  can be reduced, by moving the center lower safety shield  154  toward the first side panel  104  or toward the second side panel  106 . The center lower safety shield  160  can have a curved or semicircular cutout  161  on either or both of the laterally peripheral edges of the center lower safety shield  160 . Each end lower safety shield  156 ,  158  can also have a curved or semicircular cutout  157  on the edge facing the center lower safety shield  160 . When the lower safety shields  156 ,  158 ,  160  have cutouts  157 ,  161 , the center lower safety shield  160  and either of the end lower safety shields  156 ,  158  can be brought together while maintaining a sash opening  154  large enough to provide manual access to the work chamber  102 . For example, with a ten inch high sash and ten inch high lower safety shields  156 ,  158 ,  160 , the radius of the cutout  157 ,  161  can be 4.5 inches (0.1143 meters), and the cutout can be a half circle, leaving a straight edge 0.5 inches (0.0127 meters) long immediately above and immediately below the cutout. When the center lower safety shield  160  abuts either end lower safety shield  156 ,  158  at the 0.5 inch (0.0127 meters) long straight edge, then there is a 9 inch (0.2286 meters) circular opening  154  between the center lower safety shield  160  and the end lower safety shield  156 ,  158 . The circular opening  154  allows an operator equal freedom of movement in all directions. In other embodiments, the cutout  157 ,  161  is not a half circle. The cutouts  157 ,  161  can also have smaller radiuses than 4.5 inches (0.1143 meters), leaving longer straight edges than 0.5 inches (0.0127 meters); and the cutouts  157 ,  161  can have radiuses as large as half the sash height or larger with no straight edge immediately above or below the cutouts  157 ,  161 . The lower safety shields can have various lengths. In one embodiment, the end lower safety shields  156 ,  158  can be 10 inches long (0.254 meters), and the center lower safety shield can be 16 inches long (0.4064 meters). The particular size and shape of the lower safety shields  156 ,  158 ,  160  can be varied to accommodate various fume hood sizes and designs, in order to achieve the proper face velocity and air flow conditions. 
         [0024]    In one embodiment, the first end lower safety shield  156  and the second end lower safety shield  158  can be movable also. For example, the end lower safety shields  156 ,  158  can slidably rest on the lower rail  163 , with the upper edge of the end lower safety shields  156 ,  158 , slidably engaging the upper safety shield  150  or an upper rail  164  that engages the upper safety shield  150 . Having slidable end lower safety shields  156 ,  158  can provide an operator with more leeway in accessing the work chamber  102 . For example, slidable end lower safety shields  156 ,  158  can enable easier access to the work chamber  102  close to the first side panel  104  or the second side panel  106 . 
         [0025]    The lower safety shields  156 ,  158 ,  160 , lessen the total open area of the sash  152  while simultaneously allowing an operator to access and work in the work chamber  102  with the operator&#39;s hands and/or arms through the sash openings  154 . Because the total open area of the sash  152  is lessened, a lesser volume of air can be drawn into the fume hood  100  and exhausted from the fume hood  100 , while maintaining an adequate face velocity. For example, a 5 foot (1.524 meter) long fume hood  100  with a 4 inch by 12 inch (0.1016 meter by 0.3048 meter) exhaust opening  140 , a 30 inch deep by 60 inch long (0.762 meter deep by 1.524 meter long) work surface, a 35 inch deep by 36 inch high (0.889 meter deep by 0.9144 meter high) vented storage cabinet  122 , and a sash  152  10 inches high by 60 inches long (0.254 inches high by 1.524 meters long), with two end lower safety shields  156 ,  158  and one center lower safety shield  160 , where the end lower safety shields  156 ,  158  are 10 inches (0.254 meters) square with a 4.5 inch (0.1143 meter) radius cutout  157 , and where the center lower safety shield  160  is 16 inches (0.4064 meters) wide with two 4.5 inch (0.1143 meter) radius cutouts  161 , the face velocity can be maintained approximately at or above 80 ft/min to 120 ft/min (≈0.4 m/s to 0.6 m/s). In this example, the sash  152  has a total area of 600 square inches (≈0.387 square meters). The sash openings  154  account for approximately 367 square inches (≈0.237 square meters) and the lower safety shields  156 ,  158 ,  160  account for approximately 233 square inches (≈0.150 square meters) of area. At about 120 ft/min (≈0.6 m/s), the air exhausted from the work chamber  102  can be approximately 330 CFM (9.339 cubic meters per minute), while the air exhausted from the storage cabinets  122  can be approximately 15 CFM (0.4245 cubic meters per minute), for a total amount of air exhausted equal to about 345 CFM (≈9.763 cubic meters per minute). 
         [0026]    In addition to reducing the volume of air flowing through the fume hood  100 , the lower safety shields  156 ,  158 ,  160  act as physical barriers to protect an operator from dangerous fluid splashes or other physical harms. In particular, the center lower safety shield  160  and configuration with one sash opening  154  on each side of the center lower safety shield  160 , positions an operator in front of the center lower safety shield  160  while the operator places a hand through one or both sash openings  154 . Otherwise, an operator can stand to the side of the fume hood  100 , in front of either end lower safety shield  156 ,  158  and place one hand through only one sash opening  154 . In the latter case, the end lower safety shield  156 ,  158  can protect the operator. 
         [0027]    In some embodiments, there can be more than one center lower safety shield  160 . For example, in a relatively large fume hood, two or more center lower safety shields  160  can accommodate multiple operators working at the fume hood  100  and within the work chamber  102  simultaneously. 
         [0028]    This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.