Where Legionella Can Grow or Spread

Legionella can grow in many parts of building water systems that are continually wet, and certain devices can then spread contaminated water droplets.  Some examples of devices where Legionella can grow and/or spread through aerosolization or aspiration (when water accidentally goes into the lungs while drinking) include: 

Developing and maintaining a water management program is a multi-step, continuous process. The key steps, listed here, are explained in more detail below.

According to the CDC, among the Legionnaires’ disease cases definitely associated with health care facilities:

• 80 percent were associated with long-term care facilities,
• 18 percent with hospitals, and
• 2 percent with both
• Cases were reported from 72 unique facilities, with the number of cases ranging from one to six per facility
• 88 percent were in people 60 years of age or older

ASHRAE's recommendations regarding Legionellosis are contained in ASHRAE Standard 188-2015, Legionellosis: Risk Management for Building Water Systems, and the ASHRAE Guideline 12 -2000, Minimizing the Risk of Legionellosis Associated with Building Water Systems.

ASHRAE recommends that cooling towers should be designed, installed, operated, and maintained in accordance with ASHRAE Guideline 12 -2000 to minimize the risk of dissemination of legionella bacteria. The guideline includes recommendations for cleaning and disinfection.

According to the CDC, answer yes to one of these four questions and you are required to implement a building water management program to reduce the risk of Legionella growth and spread.  Additionally, individual devices may require a water management plan (see below).  

Legionnaires' disease bacteria (LDB) cannot survive without water, and a properly operated, well-maintained HVAC system is unlikely to be a source of problems unless water contaminated with the bacteria enters the system.  

Air conditioning units without humidifiers have not been identified as sources of LDB.  For a Legionnaires' disease outbreak to be linked directly with the HVAC system, LDB-contaminated water must enter the system, be aerosolized, and be delivered to building occupants.

Developing a Water Management Program to Reduce Legionella Growth & Spread in Buildings

This toolkit will help you develop and implement a water management program to reduce your building’s risk for growing and spreading Legionella.  If you already have a program, this toolkit will help you assess and strengthen it.  Included are practical resources to help you ensure that your water management program is comprehensive, effective, and in line with industry standards.

New Standard to Help Minimize the Risk of Legionellosis

This summer, the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. released ASHRAE Standard 188: Prevention of Legionellosis Associated with Building Water Systems – a new standard requiring that facility owners and managers implement stronger safeguards via proactive risk assessment and risk management practices aimed at preventing Legionellosis from being contracted in commercial, institutional and industrial buildings.

New Standard to Help Minimize the Risk of Legionellosis

With 12 confirmed dead and more than 120 cases of infection due to legionellosis, New York City Council has adopted legislation that requires adherence to part of ASHRAE’s newly published Legionella standard.