CDC: Cooling Towers Can Be Legionella Vectors CDC report shows need for reliable chlorine monitoring in all system types “…both open and closed-circuit cooling towers can release aerosolized water to the atmosphere. If Legionella is present, the aerosolized water can spread the bacteria over miles.” CDC.gov The CDC notes that both open and closed-circuit cooling towers can release aerosolized water into the atmosphere. If Legionella is present, the aerosolized water