Abstract: An apparatus is described for treating air for use as a coolant for machinery. The treatment includes cooling the air with water without injecting water droplets into the air stream which droplets can visibly be seen to come to rest on the machinery. The principal elements of this water treatment apparatus comprises: low water resistance evaporation means for cooling air passing therethrough; and water dispensing means for uniformly adding water to the water evaporaton means by having water exude from the water dispensing means over an area of mutual contact with the water evaporation means. Improved embodiments employ a temperature sensing mechanism for activating the air treating mechanism dependent upon the temperature of the ambient air. A further embodiment includes a water pressure regulator means for maintaining the required effluence from the water dispensing means to obtain the optimum wetting of the evaporation means.