What is ANSI/ASHRAE Standard 188?

ANSI/ASHRAE Standard 188 Legionellosis: Risk Management for Building Water Systems was originally approved and published on 26 June 2015, and was updated in 2018. The new 2018 edition clarifies compliance requirements, and is updated throughout with enforceable, code-intended language to facilitate adoption of the standard for code and regulatory purposes. More than 5 million buildings in the U.S. are within scope of the standard’s requirements.

The Standard requires at a minimum building owners to establish and practice a Water (Legionella Prevention) Management Program for facilities with any of the following:

  • Cooling towers or evaporative condensers
  • Whirlpool spas
  • Ornamental fountains
  • Misters, atomizers, air washers, humidifiers
  • Other devices that release water droplets

… And, for potable (domestic) plumbing systems if a building has:

  • Multiple housing units with a centralized hot water system
  • More than ten stories
  • Housing for occupants over the age of 65
  • Patients staying longer than 24 hours
  • An area housing or treating people with certain health factors

What is the required documentation?

The written document must include the following:

  1. A list of the water management program team members.
  2. A brief description of the building water systems, with flow diagrams, listing salient information about all the building water systems and show, in simple line diagrams, where water is received, processed, and used.
  3. A (Legionella) Hazard Analysis of Building Water Systems. In the analysis, a brief explanation is given as to why each water system does or does not present a significant potential for Legionella growth and transmission and, for those that do, whether it is a location at which Legionella control measures can be applied.
  4. (Legionella) Hazard Control Measures. Control measures are what actually reduce the risk of Legionnaires’ disease. There are many options. Selection of the right options for your facility is critical.
  5. Ongoing documented confirmation that the plan is being implemented as designed (verification) and confirmation that control is effective (validation).

What is the ongoing implementation and maintenance?

Water Management Programs require continuous ongoing implementation and maintenance. So, like most other facility management programs, it takes time, expertise, resources and independent confirmation to establish defensibility.

Below is a video playlist of ASHRAE 188 Frequently Asked Questions answered by Phigenics CTO, ASHRAE 188 Committee Member, Legionella consultant and expert Dr. William McCoy.

What facilities are in scope?


Who are the intended users of the Standard?


What is generally required for compliance?


What is specifically required for these building water systems?


What is required for health care facilities and why is there a special Annex A?

Why are so many words in italics?

Does the Standard require testing for Legionella

What is a contingency response plan?


Who is responsible for compliance?

How do I know for certain that my building is within the scope of the Standard?

What specific building water systems are covered?

What is specifically required for designing new building water systems?