Abstract:
An apparatus and method of use are disclosed for cooling one or more exercising or resting individuals with a water mist while automatically preventing the undesirable accumulation of excess water. In some embodiments, a sensor detects accumulated water on or near an individual, while other embodiments use measured climate parameters to predict water accumulation. The apparatus can be free standing, fixed to the walls or ceiling, or attached to an object on which an individual is resting or exercising. In some preferred embodiments, the apparatus is controlled according to the passing of time and/or one or more measured physiological parameters measured by sensors directed toward or attached to an individual, or embedded in an object on which an individual is resting or exercising. In some embodiments dry air is also applied either simultaneously or alternately with the mist to enhance cooling and further discourage water accumulation.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention generally relates to devices and methods for cooling individuals, and more specifically to evaporative cooling of individuals. 
       BACKGROUND OF THE INVENTION 
       [0002]    There are many circumstances wherein individuals can become overheated. Vigorous exercise is a clear example, as well as leisure activities under conditions of high temperatures and/or intense sunlight. Active and effective cooling of individuals under these circumstances can protect their health and significantly increase their comfort and enjoyment. 
         [0003]    Evaporative cooling is well known as a highly effective means for cooling individuals. Indeed, it is the mechanism by which the body cools itself through perspiration. The discomfort and potential dehydration of cooling by perspiration can be avoided through the application of a mist of water to an individual, which cools the body in essentially the same manner as perspiration, and can be even more effective than perspiration since the mist impacts the skin at a temperature significantly below body temperature, and hence absorbs more heat than an equivalent quantity of perspiration. 
         [0004]    Means for generating and applying a water mist to one or more individuals are well known, and yet not widely used. In part, this is because there is a tendency for mist to accumulate to an extent that causes discomfort due to excessive dampness of the skin, and wetting of the clothing. 
       SUMMARY OF THE INVENTION 
       [0005]    An apparatus and method of use thereof are disclosed, wherein the apparatus combines a device for applying water droplets to one or more individuals with a means for automatically limiting the application of water droplets so as to prevent excessive water accumulation, thereby cooling the one or more individuals without undesirable wetness. 
         [0006]    In preferred embodiments, the water droplets are in the form of a mist, a spray, or a shower. Some preferred embodiments utilize one or more sensors placed on or near the skin or clothing of an individual to directly measure the accumulation of water. Other preferred embodiments measure climate conditions such as the air temperature, humidity, and velocity of the ambient air, and estimate the potential for water accumulation. 
         [0007]    In some preferred embodiments, the water droplet emission device is attached to an object on which an individual is resting or exercising. In other preferred embodiments, the water droplet emission device is free standing, is built into a wall or ceiling, or is part of the climate control system for an entire room. Depending on the preferred embodiment, the device for applying water droplets controls one or more of the duration of emitting of water droplets, frequency of emitting of water droplets, numerical density of emitted water droplets, size of emitted water droplets, temperature of emitted water droplets, direction of travel of emitted water droplets, speed of travel of emitted water droplets, and rate of divergence of emitted water droplets. 
         [0008]    In some preferred embodiments, the apparatus is manually controlled, while in other preferred embodiments the apparatus is automatically controlled. In some of the latter preferred embodiments, the apparatus is controlled according to the passing of time and/or according to one or more measured physiological parameters such as the skin temperature, core body temperature, heart rate, and rate of perspiration. Physiological parameters can be measured by sensors attached to an individual or sensors embedded in an object or device on which an individual is resting or exercising. In other preferred embodiments the apparatus is automatically controlled at least partly according to the amount of activity and/or the amount of energy exerted on an exercise machine. 
         [0009]    In preferred embodiments, the water droplets are carried by a stream of air, and in some of these preferred embodiments the speed and direction of the stream of air is controlled by the apparatus. In further preferred embodiments, the humidity of the air surrounding the one or more individuals is reduced, so as to increase the cooling efficiency of the water droplets and reduce the tendency of water to accumulate. In some of these preferred embodiments, water droplets are injected either continuously or alternately into a stream of dry air. In other preferred embodiments, a separate stream of dry air is applied to the one or more individuals, either continuously or alternating with droplet application. 
         [0010]    The method of use of the invention includes providing an apparatus as described above, applying water droplets, determining the degree of water accumulation either by sensing or estimating, and limiting the application of water droplets when it is determined that too much water is accumulating. Preferred embodiments of the method include the application of dry air so as to increase the efficiency of cooling and reduce the tendency of water to accumulate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1A  is a block diagram of a general embodiment of the invention; 
           [0012]      FIG. 1B  is a functional diagram of a preferred embodiment including a mist controller that automatically determines the need for misting; 
           [0013]      FIG. 1C  is a functional diagram of a preferred embodiment similar to  FIG. 1B , in which the apparatus is able to apply dry air as well as mist; 
           [0014]      FIG. 2A  is a perspective drawing of a reclining individual being cooled by a free standing embodiment of the invention that detects water accumulation using a sensor placed near the individual and monitors the need for cooling using a skin temperature sensor attached to the forehead of the individual; 
           [0015]      FIG. 2B  is a perspective drawing of an individual sitting on a lounge chair being cooled by a free standing embodiment of the invention that estimates the water evaporation rate based on measured climate conditions and monitors the need for cooling using a core body temperature sensor attached to the lounge chair and held in contact with the neck of the individual; 
           [0016]      FIG. 2C  is a perspective drawing of an individual riding a bicycle while being cooled by a preferred embodiment of the invention that is attached to the bicycle and uses a sensor attached to the clothing of the individual to detect water accumulation; 
           [0017]      FIG. 3A  is a perspective drawing of an embodiment wherein a plurality of individuals exercising in a room is cooled by mist from the ceiling and dry air from a fan on the wall while a sensor on the floor detects any water accumulation; 
           [0018]      FIG. 3B  is a perspective drawing of an embodiment wherein a plurality of individuals exercising in a room is cooled by mist from the ceiling, while the need for cooling is monitored by skin temperature sensors attached to the foreheads of the individuals, a sensor on the floor detects any water accumulation, and a flow of dry air near the floor reduces the tendency for water to accumulate; 
           [0019]      FIG. 4A  is a perspective drawing of an individual on a stationary exercise device being cooled by a combined flow of mist and dry air from above; 
           [0020]      FIG. 4B  is a perspective drawing of an individual on a stationary exercise device being cooled by a flow of water droplets from above and a flow of dry air from below; 
           [0021]      FIG. 4C  is a perspective drawing of an individual on a stationary exercise device being cooled by a flow of water droplets from above and a flow of dry air from the room into an air intake vent located below the exercise device; 
           [0022]      FIG. 4D  is a perspective drawing of an individual on a stationary exercise device being cooled by a flow of water droplets from the front emitted by a water droplet emission device attached to the exercise device; 
           [0023]      FIG. 4E  is a perspective drawing of an individual on a stationary exercise device being cooled by a flow of water droplets from behind emitted by a water droplet emission device attached to the exercise device; 
           [0024]      FIG. 5  is a perspective drawing of a plurality of individuals on exercise devices, each being cooled from above by a separate source of water droplets combined with dry air; 
           [0025]      FIG. 6A  through  FIG. 6C  are logic diagrams that depict strategies used by water droplet accumulation limiters when sensors detect water accumulation: 
           [0026]    in  FIG. 6A  the water droplet accumulation limiter stops the application of mist and waits until the accumulated water evaporates naturally; 
           [0027]    in  FIG. 6B  the water droplet accumulation limiter stops the application of mist and initiates either the application of dry air or some other action that promotes water evaporation; and 
           [0028]    in  FIG. 6C  the water droplet accumulation limiter continues to apply mist but reduces the duration and/or intensity of the mist; 
           [0029]      FIG. 6D  through  FIG. 6F  are logic diagrams depicting strategies used by water droplet accumulation limiters when water accumulation is predicted based on measured climate parameters: 
           [0030]    in  FIG. 6D  the water droplet accumulation limiter stops the application of mist and waits for the accumulated water to evaporate naturally; 
           [0031]    in  FIG. 6E  the water droplet accumulation limiter stops the application of mist, and initiates the application of dry air or some other action that promotes water evaporation; and 
           [0032]    in  FIG. 6F  the water droplet accumulation limiter continues to apply mist but reduces the duration and/or intensity of the mist; 
           [0033]    the logic diagrams of  FIG. 6G  and  FIG. 6H  refer to preferred embodiments that include dry air application devices, depicting strategies used by water droplet accumulation limiters when sensors detect water accumulation; 
           [0034]    in  FIG. 6G  the apparatus stops applying mist but continues to apply dry air; and 
           [0035]    in  FIG. 6H  the apparatus adjusts the duration and/or the intensity of the mist and continues to apply dry air; 
           [0036]      FIG. 7A  is a graphical presentation of mist control strategies for exercising and resting individuals in preferred embodiments wherein the droplets are applied intermittently and wherein sensors are used to measure the skin temperatures of the individuals; 
           [0037]      FIG. 7B  is a graphical presentation of a mist control strategy for an exercising individual in a preferred embodiment wherein the water droplets are applied intermittently and a sensor is used to measure the deviation of the core body temperature of the individual away from a baseline temperature; 
           [0038]      FIG. 7C  is a graphical presentation of a mist control strategy for a resting individual in a preferred embodiment wherein the intensity of water droplets is varied until the cooling effect of the water droplets is sufficient to maintain a desired skin temperature; 
           [0039]      FIG. 7D  is a graphical presentation of a mist control strategy wherein the density of the mist is varied according to a measured pulse rate of an exercising individual; 
           [0040]      FIG. 7E  is a graphical presentation of a mist control strategy wherein the density of the mist is varied according to the ratio of the measured pulse rate of an exercising individual to the age related maximum pulse rate for the individual; 
           [0041]      FIG. 8  is a front drawing of a control panel for a preferred embodiment wherein the user manually adjusts the desired level of misting intensity and the maximum wetness level (in arbitrary units); 
           [0042]      FIG. 9  is a front drawing of a control panel for a preferred embodiment wherein the apparatus is automatically controlled according to the measured skin temperature and wetness of an individual as compared to user specified maximums, and wherein the apparatus controls the air flow and humidity of the air near the individual in addition to the application of mist; 
           [0043]      FIG. 10A  is an illustration of a conductivity-based wetness sensor; 
           [0044]      FIG. 10B  is an illustration of a reflectivity-based wetness sensor; and 
           [0045]      FIG. 10C  is an illustration of a machine vision based wetness sensor. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0046]    With reference to  FIG. 1A , the basic apparatus of the invention includes a water droplet application device  100 , and a water droplet accumulation limiter  102 . A request for misting  104  reaches the apparatus, either due to direct adjustment of a manual control by an individual or due to an automatically generated signal according to the passage of time and/or according to one or more measured physiological parameters. If the water droplet accumulation limiter senses that too much water is accumulating  106  then it will not allow the application of mist. Otherwise, mist is applied  108  to the individual according to the request for misting  104 . 
         [0047]    With reference to  FIG. 1B , in a more sophisticated embodiment, the apparatus includes a mist controller  110  that sends a request for mist to the water droplet application device  100  when it either measures or estimates  112  that the individual is too hot  114 . However, the water droplet accumulation limiter  102  intercepts the signal from the mist controller  110 . It measures or anticipates if there is too much water accumulating  116 , and if there is too much water accumulating  118  it blocks the signal from the mist controller  110  using a device that functions logically as a signal gate  120 . If the water droplet accumulation limiter  102  determines that too much water is not accumulating  118 , then the signal from the mist controller  110  is allowed to pass through the gate  120  and reach the water droplet application device  100 , which responds by applying mist  122  to the individual. 
         [0048]      FIG. 1C  is a logic diagram of a preferred embodiment similar to  FIG. 1B , except that the water droplet application device  100  is able to apply dry air  124  to the individual, in addition to water droplets. If the water droplet accumulation limiter  102  determines that too much water is accumulating  118 , then a signal is sent to apply dry air  124 . If the water droplet accumulation device determines that too much water is not accumulating,  118 , then the signal from the mist controller  110  is allowed to pass through the gate  120  and the water droplet application device  100  applies mist  122  followed by dry air  123 . 
         [0049]      FIG. 2A  is a perspective view of a preferred embodiment wherein cooling mist  200  is applied to an individual  202  lying down in a restful position. The water droplet application device  204  is supported by a free-standing base that includes a supply of water  206  and a mist controller  208  that regulates the intensity of the mist according to the skin temperature of the individual  202  as measured by a sensor  210 , such as a thermocouple, attached to the forehead of the individual  202 . The sensor  210  communicates with the mist controller  208  by transmitting wireless signals to an antenna  212  attached to the controller  208 . The water droplet accumulation limiter, which is located together with the mist controller  208 , uses a wetness sensor  214  placed near the individual  202  to detect if water is accumulating. 
         [0050]    In order to avoid false readings, whenever possible skin temperatures and core body temperatures are measured at locations that are not directly cooled by mist and dry air. For example, the head band in  FIG. 2A  is placed at a location where the sensor is not directly cooled by the mist. In addition, the headband is made from a water repellent material containing thermal insulation so as to further isolate the sensor from the mist, and so as to prevent any evaporative cooling of the skin region where the sensor is attached, including evaporative cooling by perspiration. In other embodiments, a tympanic membrane temperature sensor can be used, since the tympanic membrane will not be significantly cooled by the mist. In still other embodiments, the skin temperature of the individual  202  is measured by a sensor, such as an infra-red sensor, that is directed toward but not directly attached to the individual  202 . 
         [0051]    The wetness sensor can consist, for example, of two sets of conducting strips that do not make electrical contact but are placed in very close proximity to each other on an exposed surface of a printed circuit. Accumulating water droplets on the surface of the printed circuit will conductively bridge the two sets of conducting strips, thereby creating electrical conductivity between the two that can be measured and directly related to the degree of wetness on the surface. Another method of sensing wetness is to place a section of water absorbing material between two small metal plates, forming an electrical capacitor. As the water absorption of the material varies, the dielectric constant of the material changes, and the resulting change in capacitance can be related directly to the degree of wetness. For example, the capacitor can be formed as a clip that attaches to the clothing of an individual and directly measures the wetness of the clothing. Other methods include measuring the optical properties of transparent or reflective surfaces, using for example a fiber optic source and detector or a LASER source and detector directed toward but not attached to the transparent or reflective surface. 
         [0052]      FIG. 2B  is a perspective view of a preferred embodiment that is similar to the embodiment of  FIG. 2A , except that the individual  202  is resting on a reclining chair  216  and the mist controller  208  operates according to the core body temperature of the individual  202  as measured by a sensor  218  embedded in the back of the chair such that it rests against the neck of the individual  202 . In addition, instead of directly measuring water accumulation using a water sensor ( 214  in  FIG. 2A ), this embodiment estimates the rate of water evaporation using climate conditions, such as the air temperature, humidity, and wind speed, as measured by a climate sensor  220 . 
         [0053]      FIG. 2C  is a perspective view of an embodiment functionally identical to the embodiment of  FIG. 2A , except that the apparatus is attached to a bicycle  222  being ridden by the individual  202  and the water accumulation sensor  214  is attached to the clothing of the individual. 
         [0054]      FIG. 3A  is a perspective view of an exercise room  300  in which a group of individuals  302  is exercising on a mat  304  while being cooled by mist  306  emitted by water droplet application devices  308  mounted in the ceiling of the room  300 . A mist controller and a water droplet accumulation limiter are contained together in a control unit  310  that also controls a source of dry air  312 . A water sensor  314  placed on the mat  304  is used by the water droplet accumulation limiter to detect and prevent accumulation of water. 
         [0055]      FIG. 3B  is a perspective view of an embodiment similar to the embodiment of  FIG. 3A , except that the mist controller in the control unit  310  operates according to skin temperature measurements from sensors  316  attached to the foreheads of the individuals  302  and transmitted wirelessly to an antenna  318  on the control unit. Also, in this embodiment the source of dry air  312  directs a flow of dry air onto the mat  304 , so as to prevent the mat  304  from becoming slippery due to water accumulation. 
         [0056]      FIG. 4A  is a perspective view of an individual  400  exercising on an exercise device  402  while being cooled by a combined flow of water droplets  404  and dry air  406 . A water droplet emission device  408  injects water droplets into a stream of dry air from a dry air source  410 . A control unit  412  contains a mist and dry air controller that operates according to the pulse rate of the individual  400  as measured by a sensor embedded in a handle of the exercise device  402  and transmitted to the control unit  412  by a wire  414 . A water droplet accumulation limiter, also located inside of the control unit  412 , uses a water sensor  416  attached to the exercise device  402  to detect water accumulation. 
         [0057]      FIG. 4B  and  FIG. 4C  are perspective views of preferred embodiments similar to the embodiment of  FIG. 4A , except that the water droplets  404  are not injected into the flow of dry air  406 . Instead, in  FIG. 4B  the droplets  404  are applied from above the individual  400  while the flow of dry air  406  is applied from below, while in  FIG. 4C  the droplets  404  are applied from above the individual  400  while air  406  flows past the individual and into a vent  410  in the floor below the individual. 
         [0058]    In general, the evaporative cooling efficiency of mist can be enhanced by surrounding an individual with dry air, either drawn from outside if the outside air is naturally dry, or through use of a dehumidifier. 
         [0059]      FIG. 4D  is a perspective view of a preferred embodiment in which a frame  418  is used to attach the apparatus of the invention to an exercise device  402 . In this embodiment, the water droplets  404  are carried by a flow of air from a manually controlled water droplet emitting device  420  attached to containers  422  of water. The flow of air is generated by a fan contained in the water droplet emitting device  420  and powered either by a battery or by an external power source via a power cord (not shown). A water droplet accumulation limiter  424  operates according to measurements transmitted wirelessly from a water sensor  416  worn by the individual  400 . 
         [0060]      FIG. 4E  is a perspective view of an embodiment very similar to the embodiment of  FIG. 4D , except that the water droplet emitting device  420  is mounted such that the mist  404  is applied from behind the individual  400 . 
         [0061]      FIG. 5  is a perspective view of a preferred embodiment in which a plurality of individuals  500  using a plurality of exercise devices  502  are cooled by a combined flow of mist  504  and dry air  506  emitted by water droplet application devices  508  positioned above the exercise devices  502 . The water droplet application devices  508  are controlled by a single control unit  510  that contains a mist controller ( 110  in  FIG. 1B ) and a water droplet accumulation limiter ( 102  in  FIG. 1B ). The mist controller ( 110  in  FIG. 1B ) operates according to skin temperature measurements transmitted wirelessly from sensors  512  attached to the individuals  500  and received by an antenna  514  attached to the control unit  510 . The water droplet accumulation limiter ( 102  in  FIG. 1B ) operates according to water measurements transmitted wirelessly to the antenna  514  on the control unit  510  from water sensors  516  attached to the clothing of the individuals  500 . 
         [0062]    In preferred embodiments, the mist controller ( 110  in  FIG. 1B ) and/or the water droplet accumulation limiter ( 102  in  FIG. 1B ) can operate according to average measurements obtained from the plurality of individuals, or they can separately control the misting and the application of dry air to each of the individuals. In addition, airborne water droplet sensors  518  measure the density of water droplets in the air near the ground, and transmit this information wirelessly to the antenna  514  on the controller  510 . This information is used to limit the application of water droplets and prevent an excess density of water droplets in the air near the floor. 
         [0063]      FIG. 6A  through  FIG. 6C  are logic diagrams that depict strategies by which water droplet accumulation limiters that use sensors to sense water accumulation operate in preferred embodiments. In the embodiment of  FIG. 6A  mist is applied  600 , after which a comparison is made  602  between a user specified maximum water accumulation  604  and the sensor measurement  606  of water accumulation. If it is determined  608  that too much water has accumulated, then the misting stops and the system waits  610  until the excess water has evaporated. The embodiment of  FIG. 6B  is similar, except that the system does something, such as applying dry air, to encourage water evaporation  612  if it is determined  608  that too much water has accumulated. In the embodiment of  FIG. 6C , also similar to the embodiments of  FIG. 6A  and  FIG. 6B , if it is determined  608  that too much water has accumulated the system reduces the intensity and/or duration of bursts of misting  614  rather than halting the misting altogether. 
         [0064]      FIG. 6D  through  FIG. 6F  are logic diagrams that depict strategies by which water droplet accumulation limiters operate in preferred embodiments by measuring climate conditions and estimating the rate of water evaporation. In the embodiment of  FIG. 6D  mist is applied  600 , after which the air temperature and humidity are measured  616  and the water evaporation rate is estimated  618 . A correction to the estimated evaporation rate is applied  620  according to a user specified correction factor  622  that serves to compensate for errors due to factors such as wind velocity, intensity of sunshine, physical separation between the atmospheric sensor and the user, and other factors that the system is not able to measure or take into account. According to the corrected estimate, if the misting rate is determined to be greater than the evaporation rate  622 , the amount of accumulated water is calculated and the misting is halted  624  temporarily to allow the accumulated water to evaporate. 
         [0065]    The embodiment of  FIG. 6B  is similar, except that the system does something, such as applying dry air, to encourage water evaporation  612  if the misting rate is determined to be greater than the evaporation rate  622 . In the embodiment of  FIG. 6F , similar to the embodiments of  FIG. 6C  and  FIG. 6D , if the misting rate is determined to be greater than the evaporation rate  622  the system reduces the intensity and/or duration of bursts of misting  614  until the misting rate is equal to or less than the evaporation rate. 
         [0066]      FIG. 6G  and  FIG. 6H  are logic diagrams that depict strategies used in preferred embodiments wherein water droplet accumulation limiters use sensors to sense water accumulation, and wherein the controller apparatus includes means to apply dry air to the individual.  FIG. 6G  is similar to  FIG. 6B , and  FIG. 6H  is similar to  FIG. 6C , except that in both cases dry air is applied  626  after each application of mist  604 . 
         [0067]      FIG. 7A  is a graphical presentation of mist control strategies for exercising  700  and resting  702  individuals in preferred embodiments where the mist is applied intermittently  704 ,  706 . In each case, the on/off ratio  708  of the intermittent misting is adjusted according to the measured skin temperature  710  of the individual, with the on/off ratio  708  being increased linearly as the skin temperature  710  rises. 
         [0068]      FIG. 7B  is a graphical presentation of a mist control strategy  712  for an exercising individual in a preferred embodiment wherein the mist is applied intermittently  704 ,  706 . In this embodiment the misting on/off ratio  708  is increased linearly as the measured core body temperature  714  rises above a baseline temperature. 
         [0069]      FIG. 7C  is a graphical presentation of a mist control strategy  716  for a resting individual in a preferred embodiment wherein the density of water droplets  718 ,  720  is varied until a point is reached  722  where no further changes of the density  724  are needed to maintain a desired skin temperature  726 . 
         [0070]      FIG. 7D  is a graphical presentation of a mist control strategy  728  for an exercising individual wherein the density  718 ,  720 ,  730  of the water droplets is increased linearly as the measured pulse rate  732  of the individual rises. 
         [0071]      FIG. 7E  is similar to  FIG. 7D , except that the density of the water droplets  730  is linearly increased  734  as the measured heart rate approaches the age related maximum heart rate  736  for the individual. 
         [0072]      FIG. 8  is a front drawing of a control panel for a preferred embodiment wherein the user manually adjusts the desired level of misting intensity  800  and the maximum wetness level (in arbitrary units)  802 . In different embodiments the misting intensity  800  represents the on/off ration of an intermittent flow, a water droplet density of a continuous flow, an average rate of droplet application, or any other factor or combination of factors that determine the overall rate at which droplets are applied to the individual. In this embodiment, the user selects from between four levels of intensity, labeled “High,” “Medium,” “Low,” and “Off.” The maximum wetness level  802  is entered using pushbuttons to increase  804  and decrease  806  the value. 
         [0073]      FIG. 9  is a front drawing of a control panel for a preferred embodiment wherein the apparatus is automatically controlled according to the measured skin temperature and wetness of an individual as compared to user specified maximums, and wherein the apparatus controls the flow and humidity of the air near the individual in addition to the application of mist. A maximum skin temperature  900  is entered using pushbuttons  902 ,  904 , and is compared to a measured skin temperature  906 . Also, a maximum wetness level  908  (in arbitrary units) is entered using pushbuttons  910 ,  912 , and is compared to an actual wetness level  914  determined by a sensor placed on or near the individual. If the actual skin temperature  906  rises above the user specified maximum skin temperature  900 , then the mist controller requests the application of mist. If the actual wetness level  914  is below the maximum specified wetness level  908 , then the mist limiter allows the misting device to apply mist, which is indicated by a light  916  on the control panel. A fan is used to apply an air flow to the individual, either during or in between mist applications, which is also indicated by a light  918  on the front panel. Depending on the dryness of the ambient air, a built-in dehumidifier is also used to dry the air before it is applied to the individual. Once again, this is indicated by a light  920  on the front panel. 
         [0074]    If the actual wetness level  914  exceeds the user specified maximum wetness level  908 , then any requests for mist application are blocked by the mist limiter, and a light on the front panel  922  indicates this blockage, while the fan  918  and air dryer  920  indicating lights continue to indicate that dry air is being used to remove the excess water from the individual. A power indicating light  924  is also provided to indicate that the unit is switched on. 
         [0075]      FIG. 10  A through  FIG. 10C  illustrate different methods of sensing wetness. With reference to  FIG. 10A , a section of printed circuit board  1000  has two interdigitating combs of conducting material  1002 ,  1004  etched onto an exposed surface, such that the “fingers” of the two interdigitating combs  1002 ,  1004  lie close to each other but do not touch. Droplets of water  1006  landing on the surface inevitably bridge the gaps between the combs, causing conductivity and/or a change in capacitance between the two combs that can be measured with a conductivity measuring device or a capacitance measuring device. 
         [0076]    With reference to  FIG. 10B , another method for sensing wetness is by reflectivity. A section of reflective material  1008  such as a mirror is placed where wetness is to be measured. A light source  1010 , such as a LASER, directs a beam of light  1012  onto the reflective material  1008 , and the intensity of the reflected beam  1014  is measured by a light detector  1016 . As water droplets  1006  collect on the reflective surface  1006 , some of the incident light  1012  is scattered  1018 , thereby reducing the intensity of light measured by the light detector  1016 . In a similar approach (not shown), a beam of light is caused to pass through a transparent section of material, such as a piece of glass, and a light detector measures the intensity of transmitted light. Water droplets that collect on the transparent section scatter some of the light, and reduce the intensity measured by the light detector. 
         [0077]    A more sophisticated method of measuring wetness is illustrated in  FIG. 10C . A section of opaque material  1020  is placed where wetness is to be measured, and is illuminated by light  1022  from a conventional lamp  1024  or other light source. A camera  1026  is directed toward the section  1020  so that it receives light from the section  1028  and records the appearance of the section  1020 . Machine vision software (not shown) is then used to analyze the image and determine the degree of accumulated wetness. 
         [0078]    Other modifications and implementations will occur to those skilled in the art without departing from the spirit and the scope of the invention as claimed. Accordingly, the above description is not intended to limit the invention except as indicated in the following claims.