More Junk Science   In addition to the reappearance of the issues noted above by  paragraph  of Health Issues has been deleted      The paragraph stated AC achieves cooling through the process of evaporation Due to this mucous membranes in the nose and mouth get dry  the author of the offending edit seems to believe that air conditioners cause evaporation of water vapor thus drying the air in the room  This is incorrect    For clarity most air conditioners remove heat from a room by passing air over a coil in which the coolant having passed from a higher pressure region to a lower pressure region evaporates dispersing the energy in the mass of the coolant over a larger volume creating a volume of lower thermal energy relative to the air outside the coil  The second law of thermodynamics dictates that some of the heat in the air will be conducted through the metal of the coil into the coolant  The coolant is then forced into an area of higher pressure where the process is reversed with the heat leaving the coolant outside the area to be cooled  The evaporation that results in cooling happens entirely within a sealed system and can not remove moisture from the air as water vapor can not pass through the walls of the coil    If s belief were valid the evaporation would add moisture to the air not remove it      The drying effect as already explained earlier in the article is caused by condensation of water vapor already in the air  The amount of condensation and therefore dehumidification can be and in many cases is regulated by controlling the temperature of the coils  Specifically keeping the coils above the dew point will prevent condensation and may actually raise the relative humidity of the room by lowering the temperature while maintaining the absolute humidity   Some air conditioners as described in the section on evaporative coolers actually do use evaporation of water vapor  These systems do add water vapor to the air raising the absolute humidity