Most evaporative cooling systems - including drip, backwash, rotary pad and indirect types - appeared in the southwest between 1924 and 1940, all designed exclusively for refrigeration. Two other types had been developed in the north and east between 1899 and 1936. They aimed at less cooling than controlling moisture and cleaning the air in textile factories, printing plants and large factories. These units are commercial air washers and cell type air washers. More versatile than the Western types (see Chapter II), commercial air washers became universal air-processing devices. With controlled water temperature, they can heat, cool, and dehumidify as well as moisten and filter. Earlier, many served churches, auditoriums, theaters, etc. because on hot, humid days a ton of ice could be pushed through the access doors to the air washer to cool the water for a few hours of fresh air. The author recalls a church with special alley doors for Sunday ice