ASHRAE Guideline 12 provides information and guidance on the control of legionellosis associated with building water systems, and provides guidance useful in the implementation of ANSI/ASHRAE Standard 188, Legionellosis: Risk Management for Building Water Systems.

Guideline 12 applies to spaces such as hotels, office buildings, hospitals and other health care facilities, assisted living facilities, schools, universities, commercial buildings, industrial buildings, and centralized systems in multifamily residential buildings. Buildings with noncentralized water systems, and single-family residential buildings, though not included, may also benefit.

Guideline 12 does not require previous training or certification in hazard analysis, risk assessment, or risk management methodologies. It is intended for use by owners of occupied buildings and anyone involved in the design, construction, installation, commissioning, management, operation, maintenance, and service of centralized building water systems and components, and manufacturers of associated equipment.