Patent Publication Number: US-2013234347-A1

Title: Humidifying apparatus

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority of United Kingdom Application no. 1203894.9, filed Mar. 6, 2012, the entire contents of which are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a humidifying apparatus. In a preferred embodiment, the present invention provides a humidifying apparatus for generating a flow of moist air and a flow of air for dispersing the moist air within a domestic environment, such as a room, office or the like. 
     BACKGROUND OF THE INVENTION 
     A conventional domestic fan typically includes a set of blades or vanes mounted for rotation about an axis, and drive apparatus for rotating the set of blades to generate an air flow. The movement and circulation of the air flow creates a ‘wind chill’ or breeze and, as a result, the user experiences a cooling effect as heat is dissipated through convection and evaporation. The blades are generally located within a cage which allows an air flow to pass through the housing while preventing users from coming into contact with the rotating blades during use of the fan. 
     U.S. Pat. No. 2,488,467 describes a fan which does not use caged blades to project air from the fan assembly. Instead, the fan assembly comprises a base which houses a motor-driven impeller for drawing an air flow into the base, and a series of concentric, annular nozzles connected to the base and each comprising an annular outlet located at the front of the nozzle for emitting the air flow from the fan. Each nozzle extends about a bore axis to define a bore about which the nozzle extends. 
     Each nozzle is in the shape of an airfoil. An airfoil may be considered to have a leading edge located at the rear of the nozzle, a trailing edge located at the front of the nozzle, and a chord line extending between the leading and trailing edges. In U.S. Pat. No. 2,488,467 the chord line of each nozzle is parallel to the bore axis of the nozzles. The air outlet is located on the chord line, and is arranged to emit the air flow in a direction extending away from the nozzle and along the chord line. 
     Another fan assembly which does not use caged blades to project air from the fan assembly is described in WO 2010/100449. This fan assembly comprises a cylindrical base which also houses a motor-driven impeller for drawing a primary air flow into the base, and a single annular nozzle connected to the base and comprising an annular mouth through which the primary air flow is emitted from the fan. The nozzle defines an opening through which air in the local environment of the fan assembly is drawn by the primary air flow emitted from the mouth, amplifying the primary air flow. The nozzle includes a Coanda surface over which the mouth is arranged to direct the primary air flow. The Coanda surface extends symmetrically about the central axis of the opening so that the air flow generated by the fan assembly is in the form of an annular jet having a cylindrical or frusto-conical profile. 
     An inner surface of the nozzle includes a detent for co-operating with a wedge located on an external surface of the base. The detent has an inclined surface which is configured to slide over an inclined surface of the wedge as the nozzle is rotated relative to the base to attach the nozzle to the base. Opposing surfaces of the detent and the wedge subsequently inhibit rotation of the nozzle relative to the base during use of the fan assembly to prevent the nozzle from becoming inadvertently detached from the base. When a user applies a relatively large rotational force to the nozzle, the detent is arranged to flex out of engagement with the wedge to allow the user to remove the nozzle from the base. 
     SUMMARY OF THE INVENTION 
     In a first aspect, the present invention provides a fan assembly comprising a body comprising means for generating an air flow, a nozzle mounted on the body for emitting the air flow, the nozzle defining an opening through which air from outside the fan assembly is drawn by the air emitted from the nozzle, nozzle retaining means for releasably retaining the nozzle on the body, the nozzle retaining means having a first configuration in which the nozzle is retained on the body and a second configuration in which the nozzle is released for removal from the body, and a manually actuable member for effecting movement of the nozzle retaining means from the first configuration to the second configuration. 
     The provision of a manually actuable member for effecting movement of the nozzle retaining means from the first configuration to the second configuration can allow the nozzle to be rapidly and easily released for removal from the body. Once the nozzle has been released it may be pulled away from the body by a user, for example, for cleaning or replacement. 
     The nozzle retaining means is preferably biased towards the first configuration so that the nozzle is normally retained on the body. This can allow the fan assembly to be lifted by a user gripping the nozzle without the nozzle becoming accidentally released from the body. 
     The manually actuable member is preferably movable from a first position to a second position to effect movement of the nozzle retaining means from the first configuration to the second configuration. The manually actuable member may be translated or rotated from the first position to the second position. The manually actuable member may be pivotably moveable between the first and second positions. The fan assembly may comprise biasing means for biasing the manually actuable member towards the first position to reduce the risk of the manually actuable member being moved accidentally to the second position, and so require a user to apply a force to the manually actuable member to overcome the biasing force of the biasing means to move the nozzle retaining means to its second configuration. The biasing means may be in the form of one or more springs, such as a leaf spring or compression spring, or one or more resilient elements. 
     The manually actuable member is preferably located on the body of the fan assembly. The manually actuable member may be depressible by the user. The manually actuable member may be directly depressible by the user. For example part of the manually actuable member may be in the form of a button which can be pressed by a user. Alternatively, the body may comprise a separate button which is operable to move the manually actuable member to the second position. This can allow the manually actuable member to be located remotely from the external surface of the body and so be located in a more convenient position, or have a more convenient shape, for effecting the movement of the nozzle retaining means from its deployed configuration to its stowed configuration. The button is preferably located on an upper surface of the body to allow a user to apply a downward pressure to the button to overcome the biasing force of the biasing means which urges the manually actuable member towards its first position. 
     The manually actuable member is preferably in the form of a depressible catch, and so in a second aspect the present invention provides a fan assembly comprising a body comprising means for generating an air flow, a nozzle mounted on the body for emitting the air flow, the nozzle defining an opening through which air from outside the fan assembly is drawn by the air emitted from the nozzle, nozzle retaining means for releasably retaining the nozzle on the body, the nozzle retaining means having a first configuration in which the nozzle is retained on the body and a second configuration in which the nozzle is released for removal from the body, and a depressible catch for effecting movement of the nozzle retaining means from the first configuration to the second configuration. 
     The catch may be arranged to urge the nozzle away from the body as it moves from the first position to the second position to provide a visual indication to the user that the nozzle has been released for removal from the body. 
     The fan assembly may comprise catch retention means for releasably retaining the catch in its second position. By maintaining the catch in its second position, the nozzle retaining means may be retained in its second configuration. This can enable the user to release the button to remove the nozzle from the body while the nozzle retaining means is retained its second configuration. 
     In a third aspect the present invention provides a fan assembly comprising a body comprising means for generating an air flow, a nozzle mounted on the body for emitting the air flow, the nozzle defining an opening through which air from outside the fan assembly is drawn by the air emitted from the nozzle, nozzle retaining means for releasably retaining the nozzle on the body, the nozzle retaining means being moveable from a first configuration in which the nozzle is retained on the body to a second configuration in which the nozzle is released for removal from the body, and retaining means for releasably retaining the nozzle retaining means in the second configuration. The retaining means preferably comprises a moveable catch for retaining the nozzle retaining means in the second configuration. The catch is preferably moveable between a first position and a second position for retaining the nozzle retaining means in the second configuration. The retaining means preferably comprises catch retention means for retaining the catch in the second position. 
     The catch retention means may comprise one or more magnets for retaining the catch in its second position. Alternatively, the catch retention means may be arranged to engage the catch to retain the catch in its second position. In one embodiment, the catch comprises a hooked section which moves over and is retained by a wedge located on the body as it moves to its second position. 
     The nozzle preferably comprises means for urging the retaining means away from the second configuration. The nozzle is preferably arranged to urge the catch away from the catch retention means as it is replaced on the body. For example, a lower surface of the nozzle may be formed with, or comprise, a protruding member which urges the catch away from the catch retention means as the nozzle is lowered on to the body. As the catch is moved away from the catch retention means, the catch is urged by the biasing means towards its first position, which can in turn urge the nozzle retaining means towards its first configuration to retain the nozzle on the body. 
     The nozzle retaining means preferably comprises a detent which is moveable relative to the nozzle and the body to retain the nozzle on the body in the first configuration, and to release the nozzle for removal from the body in the second configuration. The detent may be located on the nozzle, but in a preferred embodiment the body comprises the detent. The catch is preferably configured to move the detent from a first, deployed position to a second, stowed position to release the nozzle for removal from the body. 
     In a fourth aspect, the present invention provides a fan assembly comprising a body comprising means for generating an air flow, and a nozzle mounted on the body for emitting the air flow, the nozzle defining an opening through which air from outside the fan assembly is drawn by the air emitted from the nozzle, wherein the body comprises a detent which is moveable relative to the nozzle from a first position for retaining the nozzle on the body to a second position for allowing the nozzle to be removed from the body, and a manually actuable member for actuating movement of the detent from the first position to the second position. 
     The body preferably comprises biasing means for biasing the detent towards the first position. The biasing means is preferably in the form of a leaf spring or a torsion spring, but the biasing means may be in the form of any resilient element. 
     The detent may be translated or rotated from the first position to the second position. Preferably, the detent is pivotably moveable between the first and second positions. The detent is preferably pivotably connected to the body, but alternatively the detent may be pivotably connected to the nozzle. The catch may be arranged to engage a lower surface of the detent as the catch moves from its first position to the second position to pivot the detent. 
     The detent is preferably arranged to engage an outer surface of the nozzle to retain the nozzle on the body. For example, the detent may be arranged to engage or enter a recessed portion of the outer surface of the nozzle to retain the nozzle on the body. 
     The nozzle preferably comprises an inlet section which is at least partially insertable into the body, and the detent may be arranged to engage the inlet section of the nozzle to retain the nozzle on the body. The inlet section of the nozzle is preferably insertable into a duct of the body to receive at least part of the air flow from the body. The duct may comprise an aperture through which the detent protrudes when in its first position to retain the nozzle on the body. 
     The nozzle retaining means may comprise a single detent. In a preferred embodiment, the nozzle retaining means comprises a plurality of detents, and the manually actuable member may be arranged to move the detents simultaneously between their deployed and stowed positions. The manually actuable member may be curved, arcuate or annular in shape so as to move each of the detents simultaneously. The detents may be located at diametrically opposed positions relative to the duct of the body. 
     The nozzle is preferably annular in shape, and extends about a bore through which air from outside the fan assembly is drawn by air emitted from the nozzle. The nozzle comprises one or more air outlets for emitting the air flow. The air outlet(s) may be located in or towards a front end of the nozzle, or towards a rear end of the nozzle. The air outlet(s) may comprise a plurality of apertures each for emitting a respective air stream, and each aperture may be located on a respective side of the bore. Alternatively, the nozzle may comprise a single air outlet extending at least partially about the bore. The nozzle may comprise an interior passage extending about the bore for conveying the air flow to the, or each, air outlet. The interior passage may surround the bore of the nozzle. 
     The fan assembly may be configured to generate a cooling air flow within a room or other domestic environment. However, the fan assembly may be arranged to change a parameter of an air flow emitted from the fan assembly. In an illustrated embodiment, the fan assembly includes humidifying means, or a humidifier, but the fan assembly may alternatively comprise one of a heater, a chiller, an air purifier and an ionizer for changing another parameter of either the first air flow or a second air flow emitted from the fan assembly. 
     For example, the body may comprise humidifying means for humidifying a second air flow. The body may comprise a base and part of the humidifying means may be housed within or connected to the base. An air inlet and the means for generating an air flow is preferably located in the base of the body. The means for generating an air flow preferably comprises an impeller and a motor for driving the impeller to generate the air flow. The impeller is preferably a mixed flow impeller. The means for generating an air flow preferably comprises a diffuser located downstream from the impeller. The base preferably comprises the duct for conveying the air flow to the nozzle. 
     In a fifth aspect, the present invention provides humidifying apparatus comprising a body and a nozzle removably mounted on the body, the body comprising means for generating a first air flow and a second air flow, and humidifying means for humidifying the second air flow, the nozzle comprising at least one first air outlet for emitting the first air flow, the nozzle defining an opening through which air from outside the apparatus is drawn by air emitted from said at least one first air outlet, the apparatus comprising at least one second air outlet for emitting the second air flow, wherein the body comprises nozzle retaining means moveable relative to the body for releasably retaining the nozzle on the body. 
     Part of the humidifying means is preferably located adjacent to the nozzle. Depending on the proximity of the humidifying means to the nozzle, the humidifying means may comprise at least one of the nozzle retaining means, the catch and the catch retention means. 
     The humidifying means preferably comprises a water tank. The body preferably comprises the water tank and a base upon which the water tank is mounted. The water tank may comprise at least the nozzle retaining means. The water tank may also comprise the catch and the catch retention means. The body preferably comprises a housing for the nozzle retention means, and within which the nozzle retention means is moveable relative to the body. This housing may also house the catch and the catch retention means. A wall of the water tank may provide the catch retention means. Alternatively, the catch retention means may be mounted on or connected to a wall of the water tank. The housing preferably comprises an aperture through which the nozzle retaining means protrudes to retain the nozzle on the body. The water tank is preferably removably mounted on the base. An aperture of the housing of the water tank may therefore align with the aperture on the duct of the base when the water tank is mounted on the base to allow the nozzle retaining means to protrude through both apertures to retain the nozzle. 
     The water tank may comprise a handle which is moveable between a stowed position and a deployed position to facilitate the removal of the water tank from the base. The water tank may comprise a spring or other resilient element for urging the handle towards the deployed position to present the handle to the user. The nozzle may be configured to urge the handle towards the stowed position, so that when the nozzle is removed from the apparatus the handle moves automatically to the deployed position to facilitate the removal of the water tank from the base. 
     In a sixth aspect, the present invention provides humidifying apparatus comprising means for generating a first air flow and a second air flow, a removable nozzle comprising at least one first air outlet for emitting the first air flow, the nozzle defining an opening through which air from outside the humidifying apparatus is drawn by air emitted from said at least one first air outlet, humidifying means for humidifying the second air flow, at least one second air outlet for emitting the second air flow, and a water tank having a handle which is moveable between a stowed position and a deployed position, and biasing means for urging the handle towards the deployed position, wherein the nozzle is configured to urge the handle towards the stowed position. 
     As the nozzle is replaced on the body, the nozzle may engage the handle to move the handle, against the biasing force of the biasing means, towards its stowed position. As the handle moves towards the stowed position, the handle may engage the catch to urge the catch away from the catch retention means to release the catch from its deployed position. The detent is preferably biased towards its deployed position. The release of the catch from its second position can allow the detent to move automatically to its deployed position to retain the nozzle on the body. 
     The water tank preferably comprises a recessed portion for storing the handle in its stowed position so that the handle does not protrude from the water tank when in its stowed position. The biasing means for biasing the handle towards its deployed position is preferably located in the recessed portion of the water tank. The biasing force is preferably in the form of a leaf spring or a torsion spring, but the biasing means may be in the form of any other spring or resilient member. The handle is preferably pivotably moveable between the stowed position and the deployed position. 
     The water tank may have a concave inner wall which is locatable adjacent, and preferably against, the duct of the base when the water tank is mounted on the base. To increase the capacity of the water tank, the water tank may be annular in shape. The water tank may therefore have a tubular inner wall which is located over and around at least an upper section of the duct of the base when the water tank is mounted on the base. The water tank may have a cylindrical outer wall. The base preferably has a cylindrical outer wall, and the water tank is preferably located on the base so that the water tank and the base are co-axial. The outer walls of the base and the water tank preferably form the outer wall of the body. The outer wall of the water tank and the outer wall of the base preferably have the same radius so that the body has a cylindrical appearance when the water tank is mounted on the base. The outer walls of the base and the water tank are preferably flush when the water tank is mounted on the base. 
     To increase further the capacity of the water tank, the water tank preferably surrounds at least an upper part of the means for generating an air flow, which in this example is a motor and impeller unit. Therefore, in a seventh aspect the present invention provides humidifying apparatus comprising a base comprising air flow generating means for generating a first air flow, a nozzle comprising at least one first air outlet for emitting the first air flow, the nozzle defining an opening through which air from outside the humidifying apparatus is drawn by air emitted from said at least one first air outlet, humidifying means for humidifying a second air flow, at least one second air outlet for emitting the second air flow, and a water tank removably mounted on the base, and wherein the water tank surrounds at least an upper section of the air flow generating means. 
     The nozzle may be mounted on the body so that the water tank surrounds a lower section of the interior passages of the nozzle. For example, the water tank may have an upper wall which is upwardly curved in shape, and the nozzle may be mounted centrally on the body so that the upper wall of the water tank covers a lower part of the external surface of the nozzle. This can allow the humidifying apparatus to have a compact appearance, and can allow the capacity of the water tank to be maximised. 
     In an eighth aspect, the present invention provides humidifying apparatus comprising a base comprising air flow generating means for generating a first air flow, a nozzle comprising an interior passage for receiving the first air flow and at least one first air outlet for emitting the first air flow, the nozzle defining an opening through which air from outside the apparatus is drawn by air emitted from said at least one first air outlet, humidifying means for humidifying a second air flow, at least one second air outlet for emitting the second air flow, and a water tank mounted on the base, and wherein the tank has an upwardly curved upper surface and the nozzle is mounted on the apparatus so that the upper surface of the water tank at least partially covers a lower section of an external surface of the nozzle. 
     A water inlet of the water tank is preferably located on a lower surface of the water tank. To fill the water tank, the water tank is removed from the base, and inverted so that the water tank can be located beneath a tap or other water source. The upper surface of the water tank preferably comprises at least one support for supporting the water tank on a work surface, for example between filling and replacement of the water tank on the base. The support(s) may be attached to the upper surface of the water tank. Alternatively, a periphery of the upper surface of the water tank may be shaped to define the support(s). The upper surface of the water tank may comprise a single curved or arcuate support. Alternatively, the upper surface of the water tank may comprise a plurality of supports located on opposite sides of the water tank. The supports are preferably parallel. 
     The humidifying means preferably comprises a water reservoir for receiving water from the water tank, and atomizing means for atomizing water in the reservoir to humidify the second air flow. The water reservoir and the atomizing means are preferably located in the base. The base preferably comprises an inlet duct for conveying the second air flow to the reservoir. The base may also comprise an outlet duct for conveying the humidified second air flow from the reservoir to the second air outlet(s). Alternatively, the water tank may comprise an outlet duct for conveying the second air flow from the reservoir. 
     The air flow generating means may comprise a first impeller and a first motor for driving the first impeller to generating the first air flow, and a second impeller for generating the second air flow. The second impeller may be driven by the first motor so that the first and second impellers are always rotated simultaneously. Alternatively, a second motor may be provided for driving the second impeller. This allows the second impeller to be driven to generate the second air flow as and when it is required by the user, and so allows an air flow to emitted from the fan assembly solely through the rear section of the fan. A common controller may be provided for controlling each motor. For example, the controller may be configured to actuate the second motor only if the first motor is currently actuated or if the second motor is actuated simultaneously with the first motor. The second motor may be deactivated automatically if the first motor is deactivated. The controller is thus preferably configured to allow the first motor to be activated separately from the second motor. 
     Alternatively, the air flow generating means may comprise a motor and an impeller for generating an air stream which is divided into the first air flow and the second air flow downstream from the impeller. The impeller is preferably a mixed flow impeller. An inlet port through which the second air flow enters the inlet duct for conveying the second air flow to the reservoir may be located immediately downstream from the impeller, or immediately downstream from a diffuser located downstream from the impeller. 
     The outlet duct may be configured to convey the second air flow to the nozzle for emission therefrom. The nozzle may be arranged to emit both a humid air flow, and a separate air flow for conveying the humid air flow away from the humidifying apparatus. This can enable the humid air flow to be experienced rapidly at a distance from the humidifying apparatus. 
     The nozzle may thus comprise at least one first air inlet, at least one first air outlet, a first interior passage for conveying the first air flow from said at least one first air inlet to said at least one first air outlet, at least one second air inlet, at least one second air outlet, and a second interior passage for conveying the second air flow from said at least one second air inlet to said at least one second air outlet. 
     The humidified second air flow can be emitted from one or more different air outlets of the nozzle. These air outlets may be positioned, for example, about the bore of the nozzle to allow the humidified air flow to be dispersed relatively evenly within the first air flow. 
     Preferably, the first air flow is emitted at a first air flow rate and the second air flow is emitted at a second air flow rate which is lower than the first air flow rate. The first air flow rate may be a variable air flow rate, and so the second air flow rate may vary with the first air flow rate. 
     The first air outlet(s) are preferably located behind the second air outlet(s) so that the second air flow is conveyed away from the nozzle within the first air flow. Each interior passage is preferably annular. The two interior passages of the nozzle may be defined by respective components of the nozzle, which may be connected together during assembly. Alternatively, the interior passages of the nozzle may be separated by a dividing wall or other partitioning member located between inner and outer walls of the nozzle. As mentioned above, the first interior passage is preferably isolated from the second interior passage, but a relatively small amount of air may be bled from the first interior passage to the second interior passage to urge the second air flow through the second air outlet(s) of the nozzle. 
     As the flow rate of the first air flow is preferably greater than the flow rate of the second air flow, the volume of the first interior passage of the nozzle is preferably greater than the volume of the second interior passage of the nozzle. 
     The nozzle may comprise a single first air outlet, which preferably extends at least partially about the bore of the nozzle, and is preferably centred on the axis of the bore. Alternatively, the nozzle may comprise a plurality of first air outlets which are arranged about the bore of the nozzle. For example, the first air outlets may be located on opposite sides of the bore. The first air outlet(s) are preferably arranged to emit air through at least a front part of the bore. The first air outlet(s) may be arranged to emit air over a surface defining part of the bore to maximise the volume of air which is drawn through the bore by the air emitted from the first air outlet(s). Alternatively, the first air outlet(s) may be arranged to emit the air flow from an end surface of the nozzle. 
     The second air outlet(s) of the nozzle may be arranged to emit the second air flow over this surface of the nozzle. Alternatively, the second air outlet(s) may be located in a front end of the nozzle, and arranged to emit air away from the surfaces of the nozzle. 
     The first air outlet(s) may therefore be located adjacent to the second air outlet(s). The nozzle may comprise a single second air outlet, which may extend at least partially about the axis of the nozzle. Alternatively, the nozzle may comprise a plurality of second air outlets, which may be arranged about the front end of the nozzle. For example, the second air outlets may be located on opposite sides of the front end of the nozzle. Each of the plurality of air outlets may comprise one or more apertures, for example, a slot, a plurality of linearly aligned slots, or a plurality of apertures. The first air outlets may extend parallel to the second air outlets. 
     Features described above in connection with the first aspect of the invention are equally applicable to each of the second to eighth aspects of the invention, and vice versa. 
    
    
     
       BRIEF DESCRIPTION OF THE INVENTION 
       An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  is a front view of a humidifying apparatus; 
         FIG. 2  is a side view of the humidifying apparatus; 
         FIG. 3  is a rear view of the humidifying apparatus; 
         FIG. 4(   a ) is a side sectional view taken along line A-A in  FIG. 1 , with the nozzle of the humidifying apparatus retained on the body, and  FIG. 4(   b ) is a similar view to  FIG. 4(   a ) but with the nozzle released from the body; 
         FIG. 5(   a ) is a top sectional view taken along line B-B in  FIG. 1 , and  FIG. 5(   b ) is a close-up of area P indicated in  FIG. 5(   a ); 
         FIG. 6(   a ) is a perspective view, from above, of the base of the humidifying apparatus with an outer wall of the base partially removed, and  FIG. 6(   b ) is a similar view to  FIG. 6(   a ) following a partial rotation of the base; 
         FIG. 7(   a ) is a perspective rear view, from above, of the water tank mounted on the base, with the handle in a deployed position, and  FIG. 7(   b ) is a close-up of area R indicated in  FIG. 7(   a ); 
         FIG. 8  is a top sectional view taken along line D-D in  FIG. 4(   a ); 
         FIG. 9  is a sectional view take along line F-F in  FIG. 8 ; 
         FIG. 10  is a rear perspective view, from below, of the nozzle; 
         FIG. 11  is a top sectional view taken along line E-E in  FIG. 4(   a ); 
         FIG. 12(   a ) is a front sectional view taken along line C-C in  FIG. 2 , with the nozzle of the humidifying apparatus retained on the body, and  FIG. 12(   b ) is a similar view to  FIG. 12(   a ) but with the nozzle released from the body; 
         FIG. 13  is a schematic illustration of a control system of the humidifying apparatus; and 
         FIG. 14  is a flow diagram illustrating steps in the operation of the humidifying apparatus. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 to 3  are external views of a fan assembly. In this example, the fan assembly is in the form of a humidifying apparatus  10 . In overview, the humidifying apparatus  10  comprises a body  12  comprising an air inlet through which air enters the humidifying apparatus  10 , and a nozzle  14  in the form of an annular casing mounted on the body  12 , and which comprises a plurality of air outlets for emitting air from the humidifying apparatus  10 . 
     The nozzle  14  is arranged to emit two different air flows. The nozzle  14  comprises a rear section  16  and a front section  18  connected to the rear section  16 . Each section  16 ,  18  is annular in shape, and extends about a bore  20  of the nozzle  14 . The bore  20  extends centrally through the nozzle  14  so that the centre of each section  16 ,  18  is located on the axis X of the bore  20 . 
     In this example, each section  16 ,  18  has a “racetrack” shape, in that each section  16 ,  18  comprises two, generally straight sections located on opposite sides of the bore  20 , a curved upper section joining the upper ends of the straight sections and a curved lower section joining the lower ends of the straight sections. However, the sections  16 ,  18  may have any desired shape; for example the sections  16 ,  18  may be circular or oval. In this embodiment, the height of the nozzle  14  is greater than the width of the nozzle, but the nozzle  14  may be configured so that the width of the nozzle  14  is greater than the height of the nozzle  14 . 
     Each section  16 ,  18  of the nozzle  14  defines a flow path along which a respective one of the air flows passes. In this embodiment, the rear section  16  of the nozzle  14  defines a first air flow path along which a first air flow passes through the nozzle  14 , and the front section  18  of the nozzle  14  defines a second air flow path along which a second air flow passes through the nozzle  14 . 
     With reference also to  FIG. 4(   a ), the rear section  16  of the nozzle  14  comprises an annular first outer casing section  22  connected to and extending about an annular inner casing section  24 . Each casing section  22 ,  24  extends about the bore axis X. Each casing section may be formed from a plurality of connected parts, but in this embodiment each casing section  22 ,  24  is formed from a respective, single moulded part. As illustrated in  FIGS. 5(   a ) and  5 ( b ), a rear portion  26  of the first outer casing section  22  is curved inwardly towards the bore axis X to define a rear end of the nozzle  14  and a rear part of the bore  20 . During assembly the end of the rear portion  26  of the first outer casing section  22  is connected to the rear end of the inner casing section  24 , for example using an adhesive. The first outer casing section  22  comprises a tubular base  28  which defines a first air inlet  30  of the nozzle  14 . 
     The front section  18  of the nozzle  14  also comprises an annular second outer casing section  32  connected to and extending about an annular front casing section  34 . Again, each casing section  32 ,  34  extends about the bore axis X, and may be formed from a plurality of connected parts, but in this embodiment each casing section  32 ,  34  is formed from a respective, single moulded part. In this example, the front casing section  34  comprises a rear portion  36  which is connected to the front end of the outer casing section  22 , and a front portion  38  which is generally frusto-conical in shape and flared outwardly from the rear portion  36  away from the bore axis X. The front casing section  34  may be integral with the inner casing section  24 . The second outer casing section  32  is generally cylindrical in shape, and extends between the first outer casing section  22  and the front end of the front casing section  34 . The second outer casing section  32  comprises a tubular base  40  which defines a second air inlet  42  of the nozzle  14 . 
     The casing sections  24 ,  34  together define a first air outlet  44  of the nozzle  14 . The first air outlet  44  is defined by overlapping, or facing, surfaces of the inner casing section  24  and the rear portion  36  of the front casing section  34  so that the first air outlet  44  is arranged to emit air from a front end of the nozzle  14 . The first air outlet  44  is in the form of an annular slot, which has a relatively constant width in the range from 0.5 to 5 mm about the bore axis X. In this example the first air outlet  44  has a width of around 1 mm. Where the inner casing sections  24 ,  34  are formed from respective components, spacers  46  may be spaced along the first air outlet  44  for urging apart the overlapping portions of the casing sections  24 ,  34  to control the width of the first air outlet  44 . These spacers may be integral with either of the casing sections  24 ,  34 . Where the casing sections  24 ,  34  are formed from a single component, the spacers  46  are replaced by fins which are spaced along the first air outlet  44  for connecting together the inner casing section  24  and the front casing section  34 . 
     The nozzle  14  defines an annular first interior passage  48  for conveying the first air flow from the first air inlet  30  to the first air outlet  44 . The first interior passage  48  is defined by the internal surface of the first outer casing section  22  and the internal surface of the inner casing section  24 . A tapering, annular mouth  50  guides the first air flow to the first air outlet  44 . The tapering shape of the mouth  50  provides for a smooth, controlled acceleration of air as it passes from the first interior passage  48  to the first air outlet  44 . A first air flow path through the nozzle  14  may therefore be considered to be formed from the first air inlet  30 , the first interior passage  48 , the mouth  50  and the first air outlet  40 . 
     The front casing section  34  defines a plurality of second air outlets  52  of the nozzle  14 . The second air outlets  52  are also formed in the front end of the nozzle  14 , each on a respective side of the bore  20 , for example by moulding or machining. Each of the second air outlets  52  is located downstream from the first air outlet  44 . In this example, each second air outlet  52  is in the form of a slot having a relatively constant width in the range from 0.5 to 5 mm. In this example each second air outlet  52  has a width of around 1 mm. Alternatively, each second air outlet  52  may be in the form of a row of circular apertures or slots formed in the front casing section  34  of the nozzle  14 . 
     The nozzle  14  defines an annular second interior passage  54  for conveying the second air flow from the second air inlet  42  to the second air outlets  52 . The second interior passage  54  is defined by the internal surfaces of the casing sections  32 ,  34 , and by the front part of the external surface of the first outer casing section  22 . The second interior passage  54  is isolated within the nozzle  14  from the first interior passage  48 . A second air flow path through the nozzle  14  may therefore be considered to be formed by the second air inlet  42 , the second interior passage  54  and the second air outlets  52 . 
     Returning to  FIG. 4(   a ) the body  12  is generally cylindrical in shape. The body  12  comprises a base  56 . The base  56  has an external outer wall  58  which is cylindrical in shape, and which comprises an air inlet  60 . In this example, the air inlet  60  comprises a plurality of apertures formed in the outer wall  58  of the base  56 . A front portion of the base  56  may comprise a user interface of the humidifying apparatus  10 . The user interface is illustrated schematically in  FIG. 13 , and described in more detail below. A mains power cable (not shown) for supplying electrical power to the humidifying apparatus  10  extends through an aperture formed in the base  56 . 
     The base  56  comprises a first air passageway  62  for conveying a first air flow to the first air flow path through the nozzle  14 , and a second air passageway  64  for conveying a second air flow to the second air flow path through the nozzle  14 . 
     The first air passageway  62  passes through the base  56  from the air inlet  60  to the first air inlet  30  of the nozzle  14 . With reference also to  FIGS. 6(   a ) and  6 ( b ), the base  56  comprises a bottom wall  66  connected to the lower end of the outer wall  58 , and a generally cylindrical inner wall  68  connected to the outer wall  58  by a recessed annular wall  70 . The inner wall  68  extends upwardly away from the annular wall  70 . In this example, the outer wall  58 , inner wall  68  and annular wall  70  are formed as a single component of the base  56 , but alternatively two or more of these walls may be formed as a respective component of the base  56 . An upper wall is connected to the upper end of the inner wall  68 . The upper wall has a lower frusto-conical section  72  and an upper cylindrical section  74  into which the base  28  of the nozzle  14  is inserted. 
     The inner wall  68  extends about an impeller  76  for generating a first air flow through the first air passageway  62 . In this example the impeller  76  is in the form of a mixed flow impeller. The impeller  76  is connected to a rotary shaft extending outwardly from a motor  78  for driving the impeller  76 . In this embodiment, the motor  78  is a DC brushless motor having a speed which is variable by a drive circuit  80  in response to a speed selection by a user. The maximum speed of the motor  78  is preferably in the range from 5,000 to 10,000 rpm. The motor  78  is housed within a motor bucket comprising an upper portion  82  connected to a lower portion  84 . The upper portion  82  of the motor bucket comprises a diffuser  86  in the form of a stationary disc having curved blades. The diffuser  86  is located beneath the first air inlet  30  of the nozzle  14 . 
     The motor bucket is located within, and mounted on, a generally frusto-conical impeller housing  88 . The impeller housing  88  is, in turn, mounted on an annular support  90  extending inwardly from the inner wall  68 . An annular inlet member  92  is connected to the bottom of the impeller housing  88  for guiding the air flow into the impeller housing  88 . An annular sealing member  94  is located between the impeller housing  88  and the annular support  90  to prevent air from passing around the outer surface of the impeller housing  88  to the inlet member  92 . The annular support  90  preferably comprises a guide portion  96  for guiding an electrical cable from the drive circuit  80  to the motor  78 . The base  56  also includes a guide wall  98  for guiding air flow the air inlet  60  to an air inlet port of the inlet member  92 . 
     The first air passageway  62  extends from the air inlet  60  to the air inlet port of the inlet member  92 . The first air passageway  62  extends, in turn, through the impeller housing  88 , the upper end of the inner wall  68  and the sections  72 ,  74  of the upper wall. 
     An annular cavity  99  is located between the guide wall  98  and the annular wall  70 . The cavity  99  has an opening which is located between the inlet member  92  and the guide wall  98  so that the cavity  99  is open to the first air passageway  62 . The cavity  99  contains a static pocket of air which serves to reduce the transmission of vibrations generated during use of the humidifying apparatus  10  to the outer surface of the body  12 . 
     The second air passageway  64  is arranged to receive air from the first air passageway  62 . The second air passageway  64  is located adjacent to the first air passageway  62 . The second air passageway  64  comprises an inlet duct  100 . With reference to  FIGS. 6(   a ) and  6 ( b ), the inlet duct  100  is defined by the inner wall  68  of the base  56 . The inlet duct  100  is located adjacent to, and in this example radially external of, part of the first air passageway  62 . The inlet duct  100  extends generally parallel to the longitudinal axis of the base  56 , which is co-linear with the rotational axis of the impeller  76 . The inlet duct  100  has an inlet port  102  located downstream from, and radially outward from, the diffuser  86  so as to receive part of the air flow emitted from the diffuser  86 , and which forms the second air flow. The inlet duct  100  has an outlet port  104  located at the lower end thereof. 
     The second air passageway  64  further comprises an outlet duct  106  which is arranged to convey the second air flow to the second air inlet  42  of the nozzle  14 . The second air flow is conveyed through the inlet duct  100  and the outlet duct  106  in generally opposite directions. The outlet duct  106  comprises an inlet port  108  located at the lower end thereof, and an outlet port located at the upper end thereof. The base  40  of the second outer casing section  32  of the nozzle  14  is inserted into the outlet port of the outlet duct  106  to receive the second air flow from the outlet duct  106 . 
     The humidifying apparatus  10  is configured to increase the humidity of the second air flow before it enters the nozzle  14 . With reference now to  FIGS. 1 to 4(   a ) and  FIG. 7 , the humidifying apparatus  10  comprises a water tank  120  removably mountable on the base  56 . The base  56  and the water tank  120  together form the body  12  of humidifying apparatus  10 . The water tank  120  has a cylindrical outer wall  122  which has the same radius as the outer wall  58  of the base  56  of the body  12  so that the body  12  has a cylindrical appearance when the water tank  120  is mounted on the base  56 . The water tank  120  has a tubular inner wall  124  which surrounds the walls  68 ,  72 ,  74  of the base  56  when the water tank  120  is mounted on the base  56 . The outer wall  122  and the inner wall  124  define, with an annular upper wall  126  and an annular lower wall  128  of the water tank  120 , an annular volume for storing water. The water tank  120  thus surrounds the impeller  76  and the motor  78 , and so at least part of the first air passageway  62 , when the water tank  120  is mounted on the base  56 . The lower wall  128  of the water tank  120  engages the outer wall  58  of the base  56 , and non-recessed parts of the annular wall  70 , when the water tank  120  is mounted on the base  56 . 
     The water tank  120  preferably has a capacity in the range from 2 to 4 litres. A window  130  is provided on the outer wall  122  of the water tank  120  to allow a user to see the level of water within the water tank  120  when it is disposed on the base  56 . 
     With reference to  FIG. 9 , a spout  132  is removably connected to the lower wall  128  of the water tank  120 , for example through co-operating threaded connections. In this example the water tank  120  is filled by removing the water tank  120  from the base  56  and inverting the water tank  120  so that the spout  132  is projecting upwardly. The spout  132  is then unscrewed from the water tank  120  and water is introduced into the water tank  120  through an aperture exposed when the spout  132  is disconnected from the water tank  120 . Once the water tank  120  has been filled, the user reconnects the spout  132  to the water tank  120 , returns the water tank  120  to its non-inverted orientation and replaces the water tank  120  on the base  56 . A spring-loaded valve  134  is located within the spout  132  for preventing leakage of water through a water outlet  136  of the spout  132  when the water tank  120  is re-inverted. The valve  134  is biased towards a position in which a skirt of the valve  134  engages the upper surface of the spout  132  to prevent water entering the spout  132  from the water tank  120 . 
     The upper wall  126  of the water tank  120  comprises one or more supports  138  for supporting the inverted water tank  120  on a work surface, counter top or other support surface. In this example, two parallel supports  138  are formed in the periphery of the upper wall  126  for supporting the inverted water tank  120 . 
     With reference also to  FIGS. 6(   a ),  6 ( b ) and  8 , the outer wall  58 , inner wall  68  and the recessed portion of the annular wall  70  of the base  56  define a water reservoir  140  for receiving water from the water tank  120 . The base  56  comprises a water treatment chamber  142  for treating water from the water tank  120  before it enters the water reservoir  140 . The water treatment chamber  142  is located to one side of the water reservoir  140 , within the recessed portion of the annular wall  70 . A cover  144  connected to the annular wall  70  comprises a water inlet  146  and a water outlet  148  of the water treatment chamber  142 . In this embodiment, each of the water inlet  146  and the water outlet  148  comprises a plurality of apertures. Water outlet  148  is located on an inclined surface of the cover  144  so that the water outlet  148  is located beneath the water inlet  146 . The cover  144  is supported by a supporting pin  150  which extends upwardly from the annular wall  70  to engage the lower surface of the cover  144 . 
     An upwardly extending pin  152  of the cover  144  is located between apertures of the water inlet  146 . When the water tank  120  is mounted on the base  56 , the pin  152  protrudes into the spout  132  to push the valve  134  upwardly to open the spout  132 , thereby allowing water to pass under gravity through the water inlet  146  and into the water treatment chamber  142 . As the water treatment chamber  142  fills with water, water flows through the water outlet  148  and into the water reservoir  140 . The water treatment chamber  142  houses a threshold inhibitor, such one or more beads or pellets  154  of a polyphosphate material, which becomes added to the water as it passes through the water treatment chamber  142 . Providing the threshold inhibitor in a solid form means that the threshold inhibitor slowly dissolves with prolonged contact with water in the water treatment chamber  142 . In view of this, the water treatment chamber  142  comprises a barrier which prevents relatively large pieces of the threshold inhibitor from entering the water reservoir  140 . In this example, the barrier is in the form of a wall  156  located between the annular wall  70  and the water outlet  148 . 
     Within the water reservoir  140 , the annular wall  70  comprises a pair of circular apertures each for exposing a respective piezoelectric transducer  160 . The drive circuit  80  is configured to actuate vibration of the transducers  160  in an atomization mode to atomise water located in the water reservoir  140 . In the atomization mode, the transducers  160  may vibrate ultrasonically at a frequency f 1 , which may be in the range from 1 to 2 MHz. A metallic heat sink  162  is located between the annular wall  70  and the transducers  160  for conveying heat away from the transducers  160 . Apertures  164  are formed in the bottom wall  64  of the base  56  to dissipate heat radiated from the heat sink  162 . Annular sealing members form water-tight seals between the transducers  160  and the heat sink  162 . As illustrated in  FIGS. 6(   a ) and  6 ( b ), the peripheral portions  166  of the apertures in the annular wall  70  are raised to present a barrier for preventing any particles of the threshold inhibitor which have entered the water reservoir  140  from the water treatment chamber  142  from becoming lodged on the exposed surfaces of the transducers  160 . 
     The water reservoir  140  also includes an ultraviolet radiation (UV) generator for irradiating water stored in the water reservoir  140 . In this example, the UV generator is in the form of a UV lamp  170  located within a UV transparent tube  172  located in the water reservoir  140  so that, as the water reservoir  140  fills with water, water surrounds the tube  172 . The tube  172  is located on the opposite side of the water reservoir  140  to the transducers  160 . One or more reflective surfaces  173  may be provided adjacent to, and preferably about, the tube  172  for reflecting ultraviolet radiation emitted from the UV lamp  170  into the water reservoir  140 . The water reservoir  140  comprises baffle plates  174  which guide water entering the water reservoir  140  from the water treatment chamber  142  along the tube  172  so that, during use, the water entering the water reservoir  140  from the water treatment chamber  142  is irradiated with ultraviolet radiation before it is atomized by one of the transducers  160 . 
     A magnetic level sensor  176  is located within the water reservoir  140  for detecting the level of water within the water reservoir  140 . Depending on the volume of water within the water tank  120 , the water reservoir  140  and the water treatment chamber  142  can be filled with water to a maximum level which is substantially co-planar with the upper surface of the pin  152 . The outlet port  104  of the inlet duct  100  is located above the maximum level of water within the water reservoir  140  so that the second air flow enters the water reservoir  140  over the surface of the water located in the water reservoir  140 . 
     The inlet port  108  of the outlet duct  106  is positioned above the transducers  160  to receive a humidified air flow from the water reservoir  140 . The outlet duct  106  is defined by the water tank  120 . The outlet duct  106  is formed by the inner wall  124  of the water tank  120  and a curved wall  180  about which the inner wall  124  extends. 
     The base  56  includes a proximity sensor  182  for detecting that the water tank  120  has been mounted on the base  56 . The proximity sensor  182  is illustrated schematically in  FIG. 13 . The proximity sensor  182  may be in the form of a reed switch which interacts with a magnet (not shown) located on the lower wall  128  of the water tank  120  to detect the presence, or absence, of the water tank  120  on the base  56 . As illustrated in  FIGS. 7(   a ),  7 ( b ) and  11 , when the water tank  120  is mounted on the base  56  the inner wall  124  and the curved wall  180  surround the upper wall of the base  56  to expose the open upper end of the upper cylindrical section  74  of the upper wall. The water tank  120  includes a handle  184  to facilitate removal of the water tank  120  from the base  56 . The handle  184  is pivotably connected to the water tank  120  so as to be moveable relative to the water tank  120  between a stowed position, in which the handle  184  is housed within a recessed section  186  of the upper wall  126  of the water tank  120 , and a deployed position, in which the handle  184  is raised above the upper wall  126  of the water tank  120 . With reference also to  FIGS. 12(   a ) and  12 ( b ), one or more resilient elements  188 , such as torsion springs, may be provided for biasing the handle  184  towards its deployed position, as illustrated in  FIGS. 7(   a ) and  7 ( b ). 
     When the nozzle  14  is mounted on the body  12 , the base  28  of the first outer casing section  22  of the nozzle  14  is located over the open end of the upper cylindrical section  74  of the upper wall of the base  56 , and the base  40  of the second outer casing section  32  of the nozzle  14  is located over the open upper end of the outlet duct  106  of the water tank  120 . The user then pushes the nozzle  14  towards the body  12 . As illustrated in  FIG. 10 , a pin  190  is formed on the lower surface of the first outer casing section  22  of the nozzle  14 , immediately behind the base  28  of the first outer casing section  22 . As the nozzle  14  moves towards the body  12 , the pin  190  pushes the handle  184  towards its stowed position, against the biasing force of the resilient elements  188 . When the bases  28 ,  40  of the nozzle  14  are fully inserted in the body  12 , annular sealing members  192  form air-tight seals between the ends of the bases  28 ,  40  and annular ledges  194  formed in the upper cylindrical section  74  of the upper wall of the base  56 , and in the outlet duct  106 . The upper wall  126  of the water tank  120  has a concave shape so that, when the nozzle  14  is mounted on the body  12 , the water tank  120  surrounds a lower part of the nozzle  14 . This not only can this allow the capacity of the water tank  120  to be increased, but can also provide the humidifying apparatus  10  with a compact appearance. 
     The body  12  comprises a mechanism for releasably retaining the nozzle  14  on the body  12 .  FIGS. 4(   a ),  11  and  12 ( a ) illustrate a first configuration of the mechanism when the nozzle  14  is retained on the body  12 , whereas  FIGS. 4(   b ) and  12 ( b ) illustrate a second configuration of the mechanism when the nozzle  14  is released from the body  12 . The mechanism for releasably retaining the nozzle  14  on the body  12  comprises a pair of detents  200  which are located on diametrically opposed sides of an annular housing  202 . Each detent  200  has a generally L-shaped cross-section. Each detent  200  is pivotably moveable between a deployed position for retaining the nozzle  14  on the body  12 , and a stowed position. Resilient elements  204 , such as torsion springs, are located within the housing  202  for biasing the detents  200  towards their deployed positions. 
     In this example, the water tank  120  comprises the mechanism for releasably retaining the nozzle  14  on the body  12 . The housing  202  comprises a pair of diametrically opposed apertures  206  which align with similarly shaped apertures  208  formed on the upper cylindrical section  74  of the upper wall of the base  56  when the water tank  120  is mounted on the base  56 . The outer surface of the base  28  of the nozzle  14  comprises a pair of diametrically opposed recesses  210  which align with the apertures  206 ,  208  when the nozzle  14  is mounted on the body  12 . When the detents  200  are in their deployed position, the ends of the detents  200  are urged through the apertures  206 ,  208  by the resilient elements  204  to enter the recesses  210  in the nozzle  14 . The ends of the detents  200  engage the recessed outer surface of the base  28  of the nozzle  14  to prevent the nozzle  14  from becoming withdrawn from the body  12 , for example if the humidifying apparatus  10  is lifted by a user gripping the nozzle  14 . 
     The body  12  comprises a depressible catch  220  which is operable to move the mechanism from the first configuration to the second configuration, by moving the detents  200  away from the recesses  210  to release the nozzle  14  from the body  12 . The catch  220  is mounted within the housing  202  for pivoting movement about an axis which is orthogonal to the axes about which the detents  200  pivot between their stowed and deployed positions. The catch  220  is moveable from a stowed position, as illustrated in  FIGS. 4(   a ),  11  and  12 ( a ), to a deployed position, as illustrated in  FIGS. 4(   b ),  7 ( a ),  7 ( b ) and  12 ( b ), in response to a user depressing a button  222  located on the body  12 . In this example, the button  222  is located on the upper wall  126  of the water tank  120  and above a front section of the catch  220 . A compression spring or other resilient element may be provided beneath the front section of the catch  220  for urging the catch  220  towards is stowed position. The rotational axis of the catch  220  is located proximate to the front section of the catch so that, as the catch  220  moves towards its deployed position, the catch  220  urges the detents  200  to pivot away from the recesses  210  against the biasing force of the resilient elements  204 . 
     The body  12  is configured to retain the catch  220  in its deployed position when the user releases the button  220 . In this example, the housing  202  of the water tank  120  comprises a wedge  224  over which a hook  226  located on the rear section of the catch  220  slides as the catch  220  moves towards its deployed position. In the deployed position, the end of the hook  226  snaps over the tapered side surface of the wedge  224  to engage the upper surface of the wedge  224 , resulting in the catch  220  being retained in its deployed position. As the hook  226  moves over the upper surface of the wedge  224 , the hook  226  engages the bottom of the handle  184  and urges the handle  184  upwardly away from the recessed section  186  of the water tank  120 . This in turn causes the handle  184  to push the nozzle  14  slightly away from the body  12 , providing a visual indication to the user that the nozzle  14  has been released from the body  12 . As an alternative to having features on the water tank  120  and the catch  220  which co-operate to retain the catch  220  in its deployed position, one or more magnets may be used to retain the catch  220  in its deployed position. 
     In its deployed position, the catch  220  holds the detents  200  in their stowed positions, as illustrated in  FIGS. 4(   b ) and  12 ( b ), to allow the user to remove the nozzle  14  from the body  12 . As the nozzle  14  is lifted from the body  12 , the resilient elements  188  urge the handle  184  to its deployed position. The user can then use the handle  184  to lift the water tank  120  from the base  56  to allow the water tank  120  to be filled or cleaned as required. 
     Once the water tank  120  has been filled or cleaned, the user replaces the water tank  120  on the base  56 , and then replaces the nozzle  14  on the body  12 . As the bases  28 ,  40  of the nozzle  14  are pushed into the body  12  the pin  190  on the nozzle  14  engages the handle  184  and pushes the handle  184  back to its stowed position within the recessed section  186  of the water tank  120 . As the handle  184  moves to its stowed position, it engages the hook  226  on the catch  220  and pushes the hook  226  away from the upper surface of the wedge  224  to release the catch  220  from its deployed position. As the hook  226  moves away from the wedge  224 , the resilient elements  204  urge the detents  200  towards their deployed positions to retain the nozzle  14  on the body  12 . As the detents  200  move towards their deployed position, the detents  200  move the catch  220  back to its stowed position. 
     A user interface for controlling the operation of the humidifying apparatus is located on the outer wall  58  of the base  56  of the body  12 .  FIG. 13  illustrates schematically a control system for the humidifying apparatus  10 , which includes this user interface and other electrical components of the humidifying apparatus  10 . In this example, the user interface comprises a plurality of user-operable buttons  240   a ,  240   b  and  240   c , and a display  242 . The first button  240   a  is used to activate and deactivate the motor  78 , and the second button  240   b  is used to set the speed of the motor  78 , and thus the rotational speed of the impeller  76 . The third button  240   c  is used to set a desired level for the relative humidity of the environment in which the humidifying apparatus  10  is located, such as a room, office or other domestic environment. For example, the desired relative humidity level may be selected within a range from 30 to 80% at 20° C. through repeated actuation of the third button  240   c . The display  242  provides an indication of the currently selected relative humidity level. 
     The user interface further comprises a user interface circuit  244  which outputs control signals to the drive circuit  80  upon actuation of one of the buttons, and which receives control signals output by the drive circuit  80 . The user interface may also comprise one or more LEDs for providing a visual alert depending on a status of the humidifying apparatus. For example, a first LED  246   a  may be illuminated by the drive circuit  80  indicating that the water tank  120  has become depleted, as indicated by a signal received by the drive circuit  80  from the level sensor  176 . 
     A humidity sensor  248  is also provided for detecting the relative humidity of air in the external environment, and for supplying a signal indicative of the detected relative humidity to the drive circuit  80 . In this example the humidity sensor  248  may be located immediately behind the air inlet  60  to detect the relative humidity of the air flow drawn into the humidifying apparatus  10 . The user interface may comprise a second LED  246   b  which is illuminated by the drive circuit  80  when an output from the humidity sensor  248  indicates that the relative humidity of the air flow entering the humidifying apparatus  10 , H D , is at or above the desired relative humidity level, H S , set by the user. 
     With reference also to  FIG. 14 , to operate the humidifying apparatus  10 , the user actuates the first button  240   a . The operation of the button  240   a  is communicated to the drive circuit  80 , in response to which the drive circuit  80  actuates the UV lamp  170  to irradiate water stored in the water reservoir  140 . In this example, the drive circuit  80  simultaneously activates the motor  78  to rotate the impeller  76 . The rotation of the impeller  76  causes air to be drawn into the body  12  through the air inlet  60 . An air flow passes through the impeller housing  88  and the diffuser  86 . Downstream from the diffuser  86 , a portion of the air emitted from the diffuser  86  enters the inlet duct  100  through the inlet port  102 , whereas the remainder of the air emitted from the diffuser  86  is conveyed along the first air passageway  62  to the first air inlet  30  of the nozzle  14 . The impeller  76  and the motor  78  may thus be considered to generate a first air flow which is conveyed to the nozzle  14  by the first air passageway  62  and which enters the nozzle  14  through the first air inlet  30 . 
     The first air flow enters the first interior passage  48  at the base of the rear section  16  of the nozzle  14 . At the base of the first interior passage  48 , the air flow is divided into two air streams which pass in opposite directions around the bore  20  of the nozzle  14 . As the air streams pass through the first interior passage  48 , air enters the mouth  50  of the nozzle  14 . The air flow into the mouth  50  is preferably substantially even about the bore  20  of the nozzle  14 . The mouth  50  guides the air flow towards the first air outlet  44  of the nozzle  14 , from where it is emitted from the humidifying apparatus  10 . 
     The air flow emitted from the first air outlet  40  causes a secondary air flow to be generated by the entrainment of air from the external environment, specifically from the region around the first air outlet  44  and from around the rear of the nozzle  14 . Some of this secondary air flow passes through the bore  20  of the nozzle  14 , whereas the remainder of the secondary air flow becomes entrained within the air flow emitted from the first air outlet in front of the nozzle  14 . 
     As mentioned above, with rotation of the impeller  76  air enters the second air passageway  64  through the inlet port  102  of the inlet duct  100  to form a second air flow. The second air flow passes through the inlet duct  100  and is emitted through the outlet port  104  over the water stored in the water reservoir  140 . The emission of the second air flow from the outlet port  104  agitates the water stored in the water reservoir  140  to generate movement of water along and around the UV lamp  170 , increasing the volume of water which is irradiated by the UV lamp  170 . The presence of the threshold inhibitor within the stored water causes a thin layer of the threshold inhibitor to be formed on the surfaces of the tube  172  and the transducers  160  which are exposed to the stored water, inhibiting the precipitation of limescale on those surfaces. This can both prolong the working life of the transducers  160  and inhibit any degradation in the illumination of the stored water by the UV lamp  170 . 
     In addition to the agitation of the water stored in the water reservoir  140  by the second air flow, the agitation may also be performed by the vibration of the transducers  160  in an agitation mode which is insufficient to cause atomization of the stored water. Depending, for example on the size and the number of transducers  160  of the base  56 , the agitation of the stored water may be performed solely by vibration of the transducers  160  at a reduced second frequency f 2 , and/or at a reduced amplitude, or with a different duty cycle. In this case, the drive circuit  80  may be configured to actuate the vibration of the transducers  160  in this agitation mode simultaneously with the irradiation of the stored water by the UV lamp  170 . 
     The agitation and irradiation of the stored water continues for a period of time sufficient to reduce the level of bacteria within the water reservoir  140  by a desired amount. In this example, the water reservoir  140  has a maximum capacity of 200 ml, and the agitation and irradiation of the stored water continues for a period of 60 seconds before atomization of the stored water commences. The duration of this period of time may be lengthened or shortened depending on, for example, the degree of agitation of the stored water, the capacity of the water reservoir  140 , and the intensity of the irradiation of the stored water, and so depending on these variables the duration of this period of time may take any value in the range of 10 to 300 seconds to achieve the desired reduction in the number of bacteria within the stored water. 
     At the end of this period of time, the drive circuit  80  actuates the vibration of the transducers  160  in the atomization mode to atomize water stored in the water reservoir  140 . This creates airborne water droplets above the water located within the water reservoir  140 . In the event that the stored water was agitated previously by vibration of the transducers  160  alone, the motor  78  is also activated at this end of this period of time. 
     As water within the water reservoir  140  is atomized, the water reservoir  140  is constantly replenished with water received from the water tank  120  via the water treatment chamber  142 , so that the level of water within the water reservoir  140  remains substantially constant while the level of water within the water tank  120  gradually falls. As water enters the water reservoir  140  from the water treatment chamber  142 , in which the threshold inhibitor is added to the water, it is guided by the walls  174  to flow along the tube  172  so that it is irradiated with ultraviolet radiation before it is atomized. 
     With rotation of the impeller  76 , airborne water droplets become entrained within the second air flow emitted from the outlet port  104  of the inlet duct  100 . The—now moist—second air flow passes upwardly through the outlet duct  106  of the second air passageway  64  to the second air inlet  42  of the nozzle  14 , and enters the second interior passage  54  within the front section  18  of the nozzle  14 . 
     At the base of the second interior passage  54 , the second air flow is divided into two air streams which pass in opposite directions around the bore  20  of the nozzle  14 . As the air streams pass through the second interior passage  54 , each air stream is emitted from a respective one of the second air outlets  52  located in the front end of the nozzle  14  in front of the first air outlet  44 . The emitted second air flow is conveyed away from the humidifying apparatus  10  within the air flow generated through the emission of the first air flow from the nozzle  14 , thereby enabling a humid air current to be experienced rapidly at a distance of several metres from the humidifying apparatus  10 . 
     The moist air flow is emitted from the nozzle  14  until the relative humidity H D  of the air flow entering the humidifying apparatus  10 , as detected by the humidity sensor  248 , is 1% at 20° C. higher than the relative humidity level H s , selected by the user using the third button  240   c . The emission of the moistened air flow from the nozzle  14  may then be terminated by the drive circuit  80 , preferably by changing the mode of vibration of the transducers  160 . For example, the frequency of the vibration of the transducers  160  may be reduced to a frequency f 3 , where f 1 &gt;f 3 ≧0, below which atomization of the stored water is not performed. Alternatively the amplitude of the vibrations of the transducers  160  may be reduced. Optionally, the motor  78  may also be stopped so that no air flow is emitted from the nozzle  14 . However, when the humidity sensor  248  is located in close proximity to the motor  78  it is preferred that the motor  78  is operated continually to avoid undesirable temperature fluctuation in the local environment of the humidity sensor  248 . Also, it is preferred to continue to operate the motor  78  to continue agitating the water stored in the water reservoir  140 . Operation of the UV lamp  170  is also continued. 
     As a result of the termination of the emission of a moist air flow from the humidifying apparatus  10 , the relative humidity H D  detected by the humidity sensor  248  will begin to fall. Once the relative humidity of the air of the environment local to the humidity sensor  248  has fallen to 1% at 20° C. below the relative humidity level H S  selected by the user, the drive circuit  80  re-activates the vibration of the transducers  160  in the atomization mode. If the motor  78  has been stopped, the drive circuit  80  simultaneously re-activates the motor  78 . As before, the moist air flow is emitted from the nozzle  14  until the relative humidity H D  detected by the humidity sensor  248  is 1% at 20° C. higher than the relative humidity level H S  selected by the user. 
     This actuation sequence of the transducers  160  (and optionally the motor  78 ) for maintaining the detected humidity level around the level selected by the user continues until button  240   a  is actuated again, or until a signal is received from the level sensor  176  indicating that the level of water within the water reservoir  140  has fallen below the minimum level. If the button  240   a  is actuated, or upon receipt of this signal from the level sensor  176 , the drive circuit  80  deactivates the motor  78 , the transducers  160  and the UV lamp  170  to switch off the humidifying apparatus  10 . The drive circuit  80  also deactivates these components of the humidifying apparatus  10  in response to signal received from the proximity sensor  182  indicating that the water tank  120  has been removed from the base  56 .