ASHRAE recently published a guideline, 'Minimizing the Risk of Legionellosis Associated with Building Water Systems'. Guideline 12 presents guidance covering a multitude of systems including cooling towers and evaporative condensers. The guideline presents a description of each system as well as an overview of the system operation including operating temperature, water droplet sizes, and nutrient availability. Recommended treatment practices are presented. The guideline emphasizes the importance of good housekeeping, biological treatment, and where possible control of the temperature level as principal control strategies. Guideline 12 is available from ASHRAE.
01-04: Cooling Towers, Evaporative Condensers, and ASHRAE Guideline 12-2000
David F. Geary, Baltimore Aircoil Company