Abstract:
A duct cleaning apparatus having one or more suction hose racks for storing straight lengths of suction tubing. Because the suction hose racks allow suction hose to be stored efficiently within the duct cleaning apparatus, the apparatus may include sufficient storage space for simultaneously storing multiple straight lengths of suction hose, a portable duct cleaning unit, a boroscope, and other tools. The duct cleaning apparatus may also have a plurality of air hoses which may be operated simultaneously to allow users to perform two or more air sweeps simultaneously on a duct.

Description:
TECHNICAL FIELD 
     This invention relates generally to duct cleaning equipment and relates, in particular, to a truck-mounted vacuum unit for cleaning the air ducts of houses and other structures. 
     BACKGROUND OF THE INVENTION 
     Houses and other buildings are commonly heated and cooled using a heating, ventilation, and air conditioning (HVAC) system. Such systems typically include a furnace for heating air. This furnace is attached at one end to a supply duct and at another end to a return duct. When the HVAC system is turned on, air moves from the interior of the house, through the supply duct, and into the furnace. The furnace then heats the air and returns the air to the interior of the house via a return duct. 
     Because, when activated, the HVAC system pumps dusty air from the interior of the house through the air ducts of the house, dust and other debris frequently accumulate on the interior of the air ducts. Such a buildup of debris can cause the quality of the air within the house to deteriorate because, as streams of air move through the ducts, debris from within the ducts may dislodge from the interior of the ducts and travel along with the air as the air flows through the ductwork and back into the house. This can adversely affect the health of those inhabiting the house. 
     To solve this problem, a technique has been developed for removing debris from within the air ducts of the HVAC system. This technique involves placing a suction source within the air ducts of the HVAC system, and then, while the suction source is activated, inserting a high-pressure air hose into the ducts upstream from the suction. The high-pressure air hose is then used to blow a stream of highly-compressed air within the ducts to dislodge debris from the interior surfaces of the ducts. The debris is then sucked into the suction source and removed from the interior of the duct. 
     To accomplish this technique, a duct-cleaning apparatus is generally used that has the following components: (1) a compressor; (2) an air hose for delivering compressed air from the compressor to the interior of the air ducts; (3) a suction source; (4) a suction hose for connecting the suction source to the interior of the air ducts; (5) a filtration system for filtering debris from the air that is removed from the air ducts; (6) a transportation platform for transporting the duct cleaning apparatus; and (7) a storage compartment for storing the air hose and suction hose during transportation. 
     To use the apparatus, a technician generally cuts a hole, sufficient to receive a suction hose, into one of the air ducts near the furnace. The technician then connects one end of the suction hose to the suction source and feeds the other end of the suction hose into the hole in the air duct. Next, the technician cuts one one-inch hole in the air duct approximately every ten feet upstream from the suction hose, and attaches a nozzle to the end of the air hose. The technician then turns the suction source on, which creates a suction within the duct, as will be discussed in more detail below. Next, the technician feeds the nozzle of the air hose through each of the one-inch holes and uses the air hose to dislodge debris from the interior of the air duct by spraying the interior of the duct with a stream of highly pressurized air. The airborne debris is then sucked into the suction source and removed from the interior of the duct. A filtration system then removes the debris from the air passing through the suction hose. 
     In order to use the air hose to remove debris from the interior of an air duct, a technician may perform either a forward or reverse “air sweep” within the duct. Before performing a reverse air sweep, the technician attaches a reverse air sweep nozzle to the end of the air hose. Such reverse air sweep nozzles include a series of jets that point back toward the air hose. After the suction source has been activated, the technician activates the air compressor and then feeds the air hose into one of the one-inch holes in the ductwork. The technician then gradually feeds the air hose upstream in the air duct in relation to the suction hose. As the air hose moves through the duct, the air hose blows air downstream against the sides of the duct and dislodges debris from the sides of the duct. 
     Before performing a forward air sweep, the technician attaches a forward air sweep nozzle to the end of the air hose. Such forward air sweep nozzles include a series of jets that point away from the air hose. After the suction source has been activated, the technician activates the air compressor and then feeds the air hose into one of the one-inch holes in the ductwork. The technician then gradually feeds the air hose downstream in the air duct in relation to the suction hose. As the air hose moves through the air duct, the air hose blows air downstream against the sides of the air ducts and dislodges debris from the sides of the duct. 
     Two different general types of duct cleaning apparatuses are currently known in the art. The first type of apparatus is a portable duct cleaner that comprises a small, portable gas-powered compressor and suction source that may be transported within the interior of a van to the building to be serviced. Once there, the portable duct cleaner is lifted from the van, wheeled into the building to be serviced and then used to clean the air ducts of the building. The disadvantage of these portable duct cleaners is that, because the duct cleaner must be small enough to fit into the back of a van, the size (and, therefore, power) of the portable compressor and suction source is limited. Also, because these portable duct cleaners tend to be heavy, two technicians are required to remove them from the transport van. A further disadvantage of these portable duct cleaners is that they are gas-powered, and therefore should not be operated within an enclosed space. One advantage of these portable duct cleaners is that, because they are small and capable of being moved within the interior of a building, they can be used to access hard-to-reach ducts. 
     A second type of prior art duct cleaning apparatus is a duct cleaning truck that comprises a large compressor and suction source mounted in a truck and powered by the power takeoff (PTO) of the truck. As shown in FIG. 7, the typical prior-art-duct cleaning truck has an array of inflatable cloth filters disposed beneath top doors that open to extend the air filters in operation. A storage compartment receives suction hose that must be coiled or bent to fit within the compartment. 
     This prior art duct cleaning truck has several disadvantages. First, because the prior art truck has a box-like storage space for storing long lengths of suction hose, a technician must bend or coil the suction hose before placing the suction hose into the storage space in order to fit the suction hose into the storage space. Over time, this may kink the suction hose and obstruct the air flow within the suction hose. Thus, the repeated coiling and bending of the suction hose over time may decrease the efficiency of the suction hose. 
     A second disadvantage of the prior art duct cleaning truck is that these trucks are only capable of storing 100-150 feet of suction hose. This is because storing the hose in a coiled position is not an efficient storage method. Also, because the coiled suction hose tends to take up a large portion of the storage space in the truck, the truck can not accommodate both 100-150 feet of suction hose and large tools, such as a boroscope or a portable duct cleaner, at the same time. 
     Another disadvantage of the prior art duct cleaning truck is that these trucks tend to fill with water when they are used in the rain. This is because, when a prior art truck is operated, the hinged top doors of the truck must be open to allow an array of inflatable cloth filters to expand above the truck, as shown in FIG.  7 . Because these filters are not waterproof, when a prior art truck is operated in the rain, rainwater tends to seep through the cloth filters and into the truck. Over time, this can cause the interior of the truck to rust. 
     Another disadvantage of prior art duct cleaning trucks is that they only contain one air hose. Because of this, it is not possible for technicians to use these trucks to simultaneously perform both a forward and a reverse air sweep on a given duct. 
     SUMMARY OF THE INVENTION 
     For ease of reference, the duct cleaning apparatus of the present invention is referred to as a “duct cleaning truck.” However, it should be understood that the duct cleaning apparatus of the present invention may also comprise a portable duct cleaning apparatus that does not include a truck base, or a stationary duct cleaning apparatus. 
     The duct cleaning truck of the present invention includes an array of horizontal racks configured to support several substantially straight lengths of suction hose. The present duct cleaning truck also includes an air inlet disposed on a rear portion of the truck, and a plurality of horizontally-disposed dry air filters that are mounted within the interior of a housing disposed on the truck. The duct cleaning truck may also include a plurality of air hoses that may be attached to an air compressor and configured to allow technicians to perform both a forward and a reverse air sweep at the same time. In addition, the duct cleaning truck may be configured to receive a boroscope and a portable air compressor within the housing of the truck. 
     Therefore, it is an object of present invention to provide an improved duct cleaning apparatus for cleaning the air ducts of houses and other structures. 
     It is a further object of the present invention to provide an improved duct cleaning apparatus that is configured to maximize space utilization within the apparatus. 
     It is a further object of the present invention to provide an improved duct cleaning apparatus that allows for the storage of one or more straight lengths of suction hose. 
     It is a further object of the present invention to provide an improved duct cleaning apparatus that allows suction hose to be stored within the truck without bending the suction hose. 
     It is a further object of the present invention to provide an improved duct cleaning apparatus that allows for the efficient storage of suction hose. 
     It is a further object of the present invention to provide an improved duct cleaning apparatus on which the doors of the suction hose storage compartment are on the same side of the truck as the air inlet. 
     It is a further object of the present invention to provide an improved duct cleaning apparatus that may be used to perform multiple air sweeps at the same time. 
     It is a further object of the present invention to provide an improved duct cleaning apparatus that may be used to clean ducts more quickly than prior art duct cleaning trucks. 
     It is a further object of the present invention to provide an improved duct cleaning apparatus with a filtration system that may be operated when the top portion of the truck is substantially closed. 
     It is a further object of the present invention to provide an improved duct cleaning apparatus that is rust-resistant. 
     Other objects, features, and advantages of the present invention will become apparent upon reading the following detailed description of the preferred embodiment of the invention, and upon considering this detailed description in conjunction with the appended drawings and claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a pictorial view of the rear of a duct cleaning truck according to a preferred embodiment of the present invention, in which the rear doors of the truck are shown open. 
     FIG. 2 is a pictorial view of the side and rear portions of the duct cleaning truck shown in FIG.  1 . This figure demonstrates the removal of suction hose from the suction hose compartment, and attachment of the hose to an air inlet on the back side of the truck. 
     FIG. 3 is a pictorial side view of the truck of FIG. 1 in which the side storage doors of the truck are shown open. 
     FIG. 4 is a cross-sectional side view of the filtration system in the truck of FIG.  1 . 
     FIG. 5 is an pictorial view of the pre-filter chamber of the truck of FIG.  1 . 
     FIG. 6 is a schematic diagram of a duct cleaning truck according to a preferred embodiment of the present invention as the truck is being used to clean a duct by simultaneously performing a forward and a reverse air sweep. 
     FIG. 7 is a pictorial view of a prior art duct cleaning truck having inflatable cloth air filters, a box-style storage space for storing coiled suction hoses, and an air inlet on a side of the truck. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Overall Structure 
     FIGS. 1-3 show the overall structure of a duct cleaning truck according to a preferred embodiment of the present invention. As shown in FIGS. 1-3, the body  41  of the duct cleaning truck has three compartments: a suction hose compartment  10 , a filter compartment  13 , and a storage compartment  30 . As shown in FIG. 1, the suction hose compartment  10  contains an array of suction hose racks  11  that are configured for storing a plurality of straight lengths of flexible suction hose  12 . As shown in FIGS. 1,  4 , and  5 , the filter compartment  13  also contains an air inlet  21  for receiving dirty air from a house or other structure, and air-filters  23  for filtering airborne particles out of the air. As shown in FIG. 3, the storage compartment  30  contains an air compressor  33 , a plurality of air reels  31 , a plurality of air hoses  32 , and has free space to receive auxiliary equipment such as a boroscope  34  and a portable duct cleaning unit  35 . The structure and contents of the duct cleaning truck  40  are discussed in more detail below. 
     Truck Body 
     The body  41  of a duct cleaning truck  40  according to a preferred embodiment of the invention includes a substantially planar back wall  42  that is partially defined by a first rear door  55  and a second rear door  56 , and a substantially planar front wall  43  parallel to the back wall  42 . A substantially planar first side wall  44  and second side wall  45  extend perpendicular to the back wall  42  and the front wall  43 , and extend between first and second side edges of the front wall  43  and the back wall  42 . A floor  46  extends perpendicular to a bottom edge of the back wall  42 , the front wall  43 , the first side wall  44 , and the second side wall  45 , and a substantially planar ceiling  47  parallel to and offset from the floor  46  extends between a top edge of the back wall  42 , the front wall  43 , the first side wall  44 , and the second side wall  45 . 
     The truck body  41  contains a vertical first compartment separator wall  48  that is parallel to, and offset from, the first side wall  44  and the second side wall  45 . This first compartment separator wall  48  is substantially planar and extends between the floor  46  and the ceiling  47  of the duct cleaning truck  40 . A rear side edge  51  of the first compartment separator wall  48  is adjacent to back wall  42  when the first and second rear doors  55 ,  56  are closed. The distance between the first compartment separator wall  48  and first side wall  44  is preferably shorter than the distance between the first compartment separator wall  48  and the second side wall  45 . 
     The truck body  41  also contains a vertical second compartment separator wall  52  that is parallel to, and offset from, the first side wall  44  and the second side wall  45 . Like the first compartment separator wall  48 , this second compartment separator wall  52  is substantially planar and extends between the floor  46  and the ceiling  47  of the duct cleaning truck  40 . A rear side edge of the second compartment separator wall  52  is adjacent to the back wall  42  of the duct cleaning truck  40 . The distance between the second compartment separator wall  52  and the first side wall  44  is preferably longer than the distance between the second compartment separator wall  52  and the second side wall  45 . 
     Suction Hose Compartment 
     The truck body  41  contains a suction hose compartment  10  that is defined by the first side wall  44 , the first vertical compartment separator wall  48 , the floor  46 , and the ceiling  47 . A technician may access the suction hose compartment  10  through a first rear opening  53  defined by a rear edge of the first side wall  44 , a rear edge of the floor  46 , a rear edge of the ceiling  47  and a rear edge of the first compartment separator wall  48 . The suction hose compartment  10  preferably occupies less than one half of the total volume of the truck body  41 . 
     Filter Compartment 
     The truck body  41  contains a filter compartment  13  defined by the first compartment separator wall  48 , the second compartment separator wall  52 , the floor  46 , the ceiling  47 , and a filter system separator wall  24  that is parallel to and offset from the back wall  42  of the duct truck. The filter system separator wall  24  is perpendicular to, and extends between, the first compartment separator wall  48  and the second compartment separator wall  52 . A technician may access the filter compartment  13  through a second rear opening  54  defined by a rear edge of the first compartment separator wall  48 , a rear edge of the second compartment separator wall  52 , a rear edge of the floor  46 , and a rear edge of the ceiling  47 . The filter compartment  13  preferably occupies less than one half of the total volume of the truck body  41 . 
     Rear Doors 
     The truck  40  includes a first rear door  55  that is pivotally connected to the truck body  41  and configured to cover the first rear opening  53  when the first rear door  55  is closed. The truck  40  also includes a second rear door  56  that is pivotally connected to the truck body  41  and configured to cover the second rear opening  54  when the second rear door  56  is closed. 
     Suction Hose Racks 
     As shown in FIG. 1, the duct cleaning truck  40  includes a plurality of suction hose racks  11  disposed within the suction hose compartment  10  and dimensioned to receive straight lengths of suction hose  12 . These racks  11  are placed along one side of the truck body  41  and preferably extend the entire length between the back wall  42  and the front wall  43  of the truck body  41 . The racks are preferably dimensioned to accommodate at least 200 feet of suction hose. 
     The suction hose racks  11  include a horizontal planar bottom portion  60  having a first side edge  61  and a second side edge  62 , a planar first side support portion  63  having a first side edge  64  and a second side edge  65 , and a planar second side support portion  66  having a first side edge  67  and a second side edge  68 . As shown in FIG. 1, the first side edge  61  of bottom portion  60  engages the second side edge  65  of first side support portion  63  along the length of the first side edge  61  of bottom portion  60 . First side support portion  63  extends diagonally up and away from bottom portion  60 . As is also shown in FIG. 1, the second side edge  62  of bottom portion  60  engages the first side edge  67  of second side support portion  66  along the length of the second side edge  62  of bottom portion  60 . Second side support portion  66  extends diagonally up and away from bottom portion  60 . 
     The suction hose racks  11  are configured so that, when a suction hose  12  is rested on a suction hose rack  11 , the bottom portion  60 , the first side support portion  63 , and the second side support portion  66  engage the suction hose  12 . This configuration serves to hold the suction hose  12  in place when the duct truck  40  is in motion. The suction hose racks  11  are also preferably configured so that, when a suction hose  12  is rested on a suction hose rack  11 , the bottom portion  60 , the first side support portion  63 , and the second side support portion  66  are in tangential relation to the suction hose  12 . The suction hose racks  11  are preferably configured so that each suction hose rack  11  may only receive a single length of suction hose  12  at a time. 
     Suction and Filtration System 
     As may be seen in FIGS. 3,  4 , and  5 , the suction and filtration system  20  of the duct cleaning truck  40  includes an air inlet  21 , disposed on a back end of the truck body  41 , that comprises a hollow cylinder that is open at a rear end  70  and a front end  71 . As shown in FIG. 1, this air inlet is preferably equidistant between first side wall  44  and second side wall  45 . The suction and filtration system  20  also includes a sunken air intake portion  72  that includes a front wall  74 , a rear wall  75  offset from and parallel to the front wall  74 , a first side wall  76  extending between and perpendicular to a first side edge of the front wall  74  and a first side edge of the rear wall  75 , and a second side wall extending between and perpendicular to a second side edge of the front wall  74  and a second side edge of the rear wall  75 . The sunken air intake portion  72  further includes a floor portion  73  perpendicular to the front, side, and rear walls of the sunken air intake portion  72  and engaging a bottom edge of the front, side, and rear walls of the sunken air intake portion  72 . The top edges of the front wall  74 , rear wall  75 , first side wall  76 , and second side wall of the sunken air intake portion  72  define a top opening  77  in the sunken air intake portion  72 . The rear wall  75  defines a hole that is in alignment with air inlet  21  so that air inlet  21  is in gaseous communication with sunken air intake portion  72 . 
     The suction and filtration system  20  also includes a prefilter chamber  22  that is defined by the various interior surfaces of the filter compartment  13 . The top opening  77  in the sunken air intake portion  72  is aligned with a hole in a portion of the floor  46  that partially defines the pre-filter chamber so that the sunken air intake portion  72  is in gaseous communication with the pre-filter chamber  22 . 
     As shown in FIG. 4, the front portion of the pre-filter chamber  22  is defined by a filter system separator wall  24 . This filter system separator wall  24  serves to separate the pre-filter chamber  22  from a post filter chamber  25  that is defined by the filter system separator wall  24 , the floor  46 , the ceiling  47 , the first compartment separator wall  48 , the second compartment separator wall  52 , and a front wall  78  of the post filter chamber  25  that is spaced apart from and parallel to filter system separator wall  24 . 
     As shown in FIG. 1, the filter system separator wall  24  defines an array of air-filter holes  29 . Each of these air-filter holes  29  is dimensioned to receive a horizontally disposed air filter  23  as shown in FIG.  4 . These air filters  23  are preferably cylindrical pleated cloth air filters. The gap between each air filter  23  and the corresponding air filter hole  29  is sealed with sealing material placed between the air filter  23  and the portion of the filter system separator wall  24  adjacent to the air filter  23 . As a result, in order for air to pass from pre-filter chamber  22  to post-filter chamber  25 , the air must pass through one or more of the air filters  23 . 
     The front wall  78  of the post-filter chamber  25  defines a blower intake hole  79 . This blower intake hole  79  is aligned with the intake of a blower  28  so that air may flow between post-filter chamber  25  and blower  28 . The outlet of blower  28  is aligned with a vertical outlet duct  26  that extends between the blower outlet and an air outlet  27 . This outlet duct  26  directs air from the outlet of blower  28  out of the duct cleaning truck  40  through air outlet  27 . 
     The air outlet  27  includes a front wall  80 , a rear wall  81  offset from and parallel to the front wall  80 , a first side wall  82  perpendicular to and extending between a first side edge of front wall  80  and a first side edge of rear wall  81 , and a second side wall  83  perpendicular to and extending between a second side edge of front wall  80  and second side edge of rear wall  81 . The top edges of the front wall  80 , the rear wall  81 , and the first and second side walls  82 ,  83  define a top opening in the air outlet  27 . The bottom edges of the front wall  80 , the rear wall  81 , and the first and second side walls  82 ,  83  define a bottom opening in the air outlet  27 . The air outlet  27  includes a horizontal outlet cap  84  spaced apart from the top opening of the air outlet  27 . This outlet cap  84  and the top edges of the front wall  80 , the rear wall  81 , and the first and second side walls  82 ,  83  of the air outlet  27  define side outlet openings through which air may flow. The outlet cap  84  prevents moisture from entering the interior of the duct cleaning truck  40 . 
     In a preferred embodiment of the invention, the blower  28  is configured to draw air through the air inlet  21 , into the sunken air intake portion  72  and the pre-filter chamber  22 , through the air filters  23 , and into the post-filter chamber  25 . The blower  28  then blows the air from the post filter chamber  25  into the outlet duct  26  and through the side openings in air outlet  27 . This process filters the air as the air passes through the air filters  23 . 
     Storage Compartment 
     The storage compartment  30  of the duct cleaning truck  40  is defined by the front wall  43  of the truck body  41 , the back wall  42  of the truck body  41 , the second side wall  45  of the truck body  41 , the suction hose racks  11 , the blower  28 , the outlet duct  26 , and the second compartment separator wall  52 . The storage compartment preferably extends from the front wall  43  to the back wall  42  of the truck body  41  and is accessible through a plurality of side access doors  85 . As shown in FIG. 3, the duct cleaning truck  40  preferably includes three upper side access doors that are pivotably attached to the truck body  41  and configured to open up and away from the truck body  41 . The duct cleaning truck also preferably includes three lower side access doors that are pivotably attached to the truck body  41  and configured to open down and away from the truck body  41 . 
     The storage compartment  30  is configured to store a standard belt-driven air-compressor  33  between the blower  28  and the front wall  43  of the truck body  41 . The storage compartment  30  is also configured to store two air reels  31  and two air hoses  32  between the second side wall  45  and the second separator wall  52 . As shown in FIG. 3, a preferred embodiment of the invention is dimensioned to simultaneously accommodate a 10 hp, 34.5 cfm air compressor  33 , two air reels  31 , two air hoses  32 , a boroscope  34 , a portable duct cleaning unit  35  and other miscellaneous tools such as ladders, air hose nozzles, and drop cloths. 
     Use of the Preferred Embodiment 
     To use the preferred embodiment of the duct cleaning truck of the present invention, a technician first parks the truck near the house or other building to be serviced. The technician then opens one or more rear doors  55  that partially define the suction hose compartment  10  so that the technician has access to the lengths of suction hose  12  stored within the body  41  of the truck. As shown in FIG. 2, the technician then removes a section of suction hose  12  from the duct cleaning truck  40  and connects one end of the section of suction hose  12  to the air inlet  21  disposed at the rear of the duct cleaning truck  40 . As shown in FIG. 6, the technician may then remove some or all remaining sections of suction hose  12  and connect the sections of suction hose  12  so that they form a continuous length of suction hose  100  that extends from the air inlet  21  to an air duct near the furnace of the building. The technician then cuts a hole in the air duct near the furnace and connects the free end of the continuous length of suction hose  100  to the hole in the customary manner. 
     The technician then opens one or more side doors  85  that partially define the storage compartment  30  of the truck  40  so that the technician has access to the air reels  31  and air hoses  32 . Technicians may then attach an appropriate nozzle to an end of each air hose  32 , activate the blower  28  and the air compressor  33 , and then use the two air hoses  32  to simultaneously perform two air sweeps within the ducts using the techniques described above. For example, as shown in FIG. 6, if the technicians desire to clean a straight 20-foot section of duct that is positioned so that the technicians can not access the section in order to cut a 1-inch hole in the middle of the section, the technicians may cut a 1-inch hole at the upstream end of the 20-foot section of duct and a 1-inch hole at the downstream end of the 20-foot section of duct. The user may then clear debris  104  from the interior of the 20-foot section of duct by simultaneously performing a reverse air sweep through the downstream 1-inch hole and a forward air sweep through the upstream 1-inch hole as shown in FIG.  6 . In other situations, the two air hoses  32  may also be used to simultaneously perform two reverse air sweeps, or two forward air sweeps. The advantage of performing a plurality of air sweeps simultaneously is that it reduces the time needed to clean a given length of air duct. 
     As mentioned above, when the air sweeps are performed, debris  104  is dislodged form the interior surfaces of the ducts so that the debris  104  becomes airborne. Once airborne, the debris  104  is sucked through the duct and into the continuous length of suction hose  100  as shown in FIG.  6 . As may be understood from FIG. 4, the debris  104  is then sucked through air inlet  21 , through sunken air intake portion  72  and pre-filter chamber  22 , and into the array of air filters  23  where the debris  104  is filtered from the air. The blower  28  then blows the filtered air through outlet duct  26  and out air outlet  27 . The debris  104  may later be removed from the air filters  23  by washing the air filters with water. 
     If desired, the technicians may remove a portable duct cleaning unit  35  from the duct cleaning truck  40  and use the portable duct cleaning unit  35  to clean portions of the duct that are difficult to reach with the truck-mounted duct cleaning apparatus. In addition, after cleaning the ducts, the technicians may remove a portable boroscope  34  from the truck and use the boroscope  34  to probe the interior of the ducts to verify that all debris has been removed from the interior surfaces of the ducts. 
     CONCLUSION 
     While this invention has been described in specific detail with reference to the disclosed embodiments, it will be understood that many variations and modifications may be made within the spirit and scope of the invention as described in the appended claims.