Ashrae Standard188 – Legionellosis: Risk Management for Building Water Systems

Below is part of the forward from the ANSI/ASHRAE Standard 188-2015 PDF.  For a fee, from the ASHRAE bookstore, you can download the entire PDF and Standard by clicking any of the blue buttons below.   

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Approved by the ASHRAE Standards Committee on May 27, 2015; by the ASHRAE Board of Directors on June 4, 2015; and by the American National Standards Institute on June 26, 2015.

(This foreword is not part of this standard. It is merely informative and does not contain requirements necessary for conformance to the standard. It has not been processed according to the ANSI requirements for a standard and may contain material that has not been subject to public review or a consensus process. Unresolved objectors on informative material are not offered the right to appeal at ASHRAE or ANSI.)

FOREWORD – ASHRAE Standard 188

The purpose of ASHRAE Standard 188 is to establish minimum legionellosis risk management requirements for building water systems.  “Legionellosis” refers to two distinct clinical illnesses.  When the bacterium Legionella causes pneumonia, the disease is referred to as “Legionnaires’ disease” (LD). The Centers for Disease Control and Prevention (CDC) estimates that each year there are between 8000 and 18,000 cases of LD in the United States and that more than 10% of these cases are fatal. Legionella can also cause a less-severe influenza-like illness known as “Pontiac fever.” Most cases of legionellosis are the result of exposure to Legionella associated with building water systems. 

The presence of Legionella bacteria in building water systems is not in itself sufficient to cause LD. Other necessary factors include environmental conditions that promote the  growth of Legionella, a means of transmitting the bacteria to people in the building (e.g., aerosol generation), and exposure of susceptible persons to colonized water that is inhaled or aspirated into the lungs. Legionella bacteria are not transmitted person-to-person or from normal (nonaspirated) ingestion of contaminated water. Susceptible persons at high risk for legionellosis include but are not limited to the elderly, dialysis patients, persons who smoke, and persons with underlying medical conditions that weaken the immune system. 

This standard is intended for use by owners and managers of human-occupied buildings and those involved in the  design, construction, installation, commissioning, operation, maintenance, and service of centralized building water systems and components.  

Standard 188 consists of numbered normative sections  followed by normative and informative annexes. The normative sections and normative annex specify the requirements to  comply with this standard. The informative annexes and informative bibliography are provided for guidance that may be helpful for a given building water system. Building water systems vary substantially in their design and their capability for transmission of Legionella. Scientific evidence is either lacking or inconclusive in certain aspects of Legionella control. Therefore, the informative annexes and informative bibliography to this document provide suggestions, recommendations, and references to guidance. 

ASHRAE Standing Standard Project Committee (SSPC) 188 has devoted a considerable amount of time and thought to resolving the concerns of affected and interested parties. The committee thanks everyone who participated in the development of the standard, especially those who made public review comments.

Because changes to improve the standard are anticipated,   Standard 188 is now on continuous maintenance, permitting it to be updated through the publication of approved addenda. The planned schedule for republication with approved addenda and errata is anticipated to be every third year.

The purpose of this standard is to establish minimum Legionellosis risk management requirements for building water


2.1 This standard provides minimum legionellosis risk management requirements for the design, construction, commissioning, operation, maintenance, repair, replacement, and expansion of new and existing buildings and their associated (potable and nonpotable) water systems and components.

2.2 This standard applies to human-occupied commercial, institutional, multi unit residential, and industrial buildings. This standard does not include single-family residential buildings. Only where specifically noted in this standard shall certain building water systems or parts of building water systems be exempt.

2.3 This standard is intended for use by owners and managers of human-occupied buildings, excluding single-family residential buildings. This standard is also intended for those involved in the design, construction, installation, commissioning, operation, maintenance, and service of centralized building water systems and components

Click below to download and read the entire ASHRAE Standard 188-2015. There is a fee from ASHRAE for the document.

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