Resources On How to Reduce the Risk of Legionella

ASHRAE resources provide a comprehensive approach to preventing the growth and spread of Legionella in buildings.

ASHRAE has developed resources to help reduce the risk of Legionella, including Standard 188, which provides a comprehensive approach to help prevent the growth and spread of Legionella within building water systems.

“With the recent outbreak of Legionnaires’ disease in Atlanta, we would like to increase awareness of the resources available to help minimize health risks associated with building water systems,” said Darryl K. Boyce, P. Eng, 2019-20 ASHRAE President.

The CDC estimates approximately 6,100 cases of Legionnaires’ disease in the United States each year. Most of those cases result from exposure to Legionella found in building water systems.

In 2018, ASHRAE published a revised edition of Standard 188, which designers and building operators can use to help establish water management plans specific to the systems in particular buildings, campuses or health care facilities. Guideline 12, Minimizing the Risk of Legionellosis Associated with Building Water Systems, is currently in revision and provides more detailed descriptions of best practices.

The 2018 edition of Standard 188 provides:


  • A description of environmental conditions that promote the growth of Legionella, such as water temperature fluctuations, water pressure changes and water stagnation.
  • Minimum Legionellosis risk management requirements for buildings and associated potable and non-potable water systems.
  • Requirements for Legionellosis control strategies and documentation.
  • Clarification of compliance requirements, as well as an update to enforceable, code-intended language to facilitate adoption of the standard for code and regulatory purposes.