Why might a heating hot water system supplying air handling units not be a likely control location for Legionella?

The reason that the supply of heated hot water to air handling units is not considered a likely control location for Legionella is due to the potential for exposure it presents. Air handling units generally do not create the conditions favorable for the proliferation of Legionella bacteria. The primary concern for Legionella growth is typically environments that allow for water stagnation, warmth, and aerosolization, which is not characteristic of systems designed primarily for heating and ventilation.

Heated hot water systems, when functioning properly, maintain higher temperatures which further diminishes the risk of Legionella growth. Additionally, the design of these systems often minimizes the formation of aerosols that could spread the bacteria into the air, thus reducing the likelihood of exposure to individuals within the building.

This context helps to clarify why this choice is seen as the most accurate in identifying why a heating hot water system is less likely to be a control location for Legionella.