Is Your Building at Risk? | How to Prevent a Legionnaires’ Outbreak

Building owners and operators should be aware of recent changes regarding recommended measures to protect building water systems against Legionella contamination. Prior measures, largely focused on inhibiting biological growths within cooling towers may not suffice to protect building occupants from exposure to this dangerous infection-causing bacterium which can grow in any building water system. Though publicly known since its 1976 outbreak in Philadelphia made national headlines, reports of Legionnaire cases have escalated, despite efforts at prevention. As pointed out in this 2016 Washington Post article, Legionnaire’s diseases continues to rise, with a 15-fold increase in reported outbreaks of the disease since the year 2000.  CDC Director Tom Frieden notes that:

“Large recent outbreaks in New York City and Flint, Michigan have brought attention to the disease and highlight the need to understand why the outbreaks occur and how best to prevent them.”

The American Society of Refrigeration and Air Conditioning Engineers has provided more thorough requirements for the control of legionella with the latest ANSI/ASHRAE Standard 188-2015. Prior publications by ASHRAE regarding Legionella were in the form of guidelines. Publication of ANSI/ASHRAE 188-2015 as a Standard essentially ensures that it will eventually be incorporated into legally binding local building regulations by simple reference. In 2016 New York City and New York State each made compliance with ASHRAE 188 as part of its requirements for building owner/operators. In addition, both mandate the registration of all existing and new cooling towers in operation since September 2015, with mandatory testing for the presence of Legionella every 90 days.

ANSI/ASHRAE 188-2015 provides guidance to both HVAC system designers and building owner/operators to minimize the risk of Legionella bacteria development. All water sources and systems in the building, including open- and closed-loop cooling tower water systems, fountains, spas, pools, and humidifiers must receive close attention. The guideline outlines general requirements for a Water Management Program, including survey, analysis, how to monitor and control, response and corrective action plans, and proper documentation. The Water Management Program serves as a crucial piece to an overall management strategy that protects buildings and occupants from potential infection caused by all water sources within the building.

A variety of support tools including this toolkit from the Centers for Disease Control (CDC)  provide guidance for dealing with this issue.

For professional support in preparing a Water Management Plan in accordance with ANSI/ASHRAE 188-2015 in your building, contact GHT Limited.

Sun, Lena H. (2016, June 7). Legionnaires’ outbreaks: Cases nearly quadrupled in 15 years. The Washington Post. Retrieved from

As the Studio Leader for GHT’s Operations & Energy Services (OES) studio, Robert Menuet, PE, CEM oversees the firm’s efforts to provide Building Energy Services, Commissioning, and Building Operations consulting. Rob has also built a national reputation for the design of innovative power and cooling infrastructure for mission critical facilities.