To avoid water shortages, conservation and re-use of water have become a necessity in many areas. Water can be purified, cooled, and re-used. Large industrial water users are power plants, manufacturers of paper, petroleum products, rayon, linens, textiles, lactose, sugar, explosives, hydrogen, rubber, steel, and so forth. Requirements are frequently in excess of 300 lb of water per lb of finished product. Water usage has doubled in the past decade—hence selection of cooling equipment becomes more important as power demands increase, industries expand, and new processes are perfected. Mechanical-draft cooling towers can cool water evaporatively to a temperature approaching the wet-bulb temperature of the ambient air. This evaporative method requires less than 1 per cent evaporation of the water circulated to dispose of the heat load economically. Air-cooled finned-tube exchangers are having increased acceptance and usage for “high-level heat removal” (for example, above 130 F referred to 100 F dry-bulb air), where water is scarce, expensive, and/or badly polluted; small space requirements and easy control are other features. The performance and life of any piece of cooling equipment is directly dependent upon its inherent qualities, type of service, severity of operation, general care and maintenance, and climatic environment.