<P> The evaporative cooler was the subject of numerous US patents in the 20th century ; many of these , starting in 1906 , suggested or assumed the use of excelsior ( wood wool ) pads as the elements to bring a large volume of water in contact with moving air to allow evaporation to occur . A typical design , as shown in a 1945 patent , includes a water reservoir ( usually with level controlled by a float valve ) , a pump to circulate water over the excelsior pads and a centrifugal fan to draw air through the pads and into the house . This design and this material remain dominant in evaporative coolers in the American Southwest , where they are also used to increase humidity . In the United States , the use of the term swamp cooler may be due to the odor of algae produced by early units . </P>
where did the term swamp cooler come from
the odor of algae produced by early units