This monograph gives guidance to health care facilities on how to comply with ASHRAE Standard 188: Legionellosis: Risk Management for Building Water Systems. Without proper guidance, hospitals may take steps that are not required; steps that may be unnecessarily costly; or steps that are not helpful in reducing the threat from legionellosis and other waterborne pathogens. This monograph provides a summary of the threat of legionellosis; gives an overview of ASHRAE 188 requirements; outlines recommended steps for compliance including the creating of an overall water risk management plan; addresses maintenance procedures, monitoring strategies, and emergency responses; and provides additional information on potential pathogens and possible response methods.