Which type of cooling systems is not associated with Legionella pneumophilia?

Air-cooled units are not typically associated with Legionella pneumophila because this bacterium thrives in water environments where it can multiply, such as cooling towers and other water-cooled systems. Air-cooled systems, on the other hand, rely on air instead of water for heat exchange, significantly reducing the potential habitat for Legionella.

In contrast, water-cooled units, evaporative condensers, and chilled water systems all involve the use of water in their operation, which can provide the warm, stagnant conditions suitable for the growth of Legionella. These systems can accumulate water that is at an optimal temperature for bacterial growth, particularly if not properly maintained. Therefore, the risk of Legionella contamination is inherently linked to any system that uses water for cooling, making air-cooled units the least likely to be involved with Legionella pneumophila.