4 Ways to Minimize Legionella Risk

Knowing Who, What, When and Why

  • 26 février 2019
  • Author: Dominick Tuzzo
  • Number of views: 6124

“An ounce of prevention is worth a pound of cure” – Benjamin Franklin

Simply defined:  Risk Management is the process of identification, analysis, and either acceptance, or control of risks you’ve identified.

  1. Risk Identification
    ANSI/ASHRAE Standard 188-2018 “Legionellosis:  Risk Management for Building Water Systems” www.ashrae.org calls upon owners and operators of ALL buildings (with the exception of single family residential dwellings) to perform an annual physical survey of their buildings and equipment in order to determine the presence of certain high-risk factors requiring the development of a site specific WMP (Water Management Plan) to mitigate these risks.
  2. Risk Analysis
    A Hazard Analysis (also known as a Risk Assessment) is a systematic evaluation of the hazardous conditions found in your particular building water systems and equipment.

    Once you’ve identified and analyzed your hazards, you have a vitally important choice to make; you may choose to either accept the risk, or you may begin to control your risk.
  3. Risk Acceptance
    Risk is a probability or threat of damage, injury, liability, loss, or any other negative occurrence that is caused by external or internal vulnerabilities, which may be avoided through preemptive action (control) to reduce it.  Acceptance or control of risk is often governed by two important factors:
  • Probability of Occurrence:  How likely is this to happen in my building?  If, during the risk identification (physical survey) phase you’ve previously identified high risk devices, occupants, or physical characteristics in your building, you probably will want to mitigate your risk by implementing specific control measures.
  • Impact of Occurrence:  What happens now?  Do I perform expensive and time consuming remediation?  Was anyone injured?  What is my liability?  Do I involve my legal department?  What about our branding?  What are my consequences?
  1. Risk Control
    The Legionella toolkit available from CDC www.cdc.gov/legionella/wmp/toolkit  was specifically designed to help you to develop and implement a WMP to reduce your building’s risk for growing and spreading Legionella.  CDC says:  “You should develop a water management program to reduce Legionella growth and spread that is specific to your building.”

After you’ve identified and analyzed your risks, the next logical step is determining how to control them via what ASHRAE calls:  Control Measures.

To adequately manage risk, a properly designed WMP should clearly define the WHO, WHAT, WHERE, WHEN, HOW and WHY of the Plan.

  • Your Program Team:  provides the WHO’s of the WMP
  • Hazard Analysis / Risk Assessment:  shows us WHAT is potentially hazardous in our particular building, system, equipment
  • Control Locations:  determines WHERE control measures need to be applied
  • Control Limits:  establishes WHEN to perform corrective actions on your systems
  • Control Measures:  explains HOW to maintain desired control limits on predetermined control locations, in order to reduce risk
  • Regulations, Codes, & Standards:  explains WHY a WMP is needed in your building

For assistance in controlling your buildings water borne pathogen risks via a site specific Water Management Plan, contact your Chem-Aqua Water Risk Management Services Group today at 1-866-209-3373.



  1. American Industrial Hygiene Association (AIHA), Recognition, Evaluation, and Control of Legionella in Building Water Systems, 2015.
  2. Department of Veterans Affairs, Veterans Health Administration, VHA Directive 1061.
  3. Association of Water Technologies (AWT), Legionella 2003:  An Update and Statement by the Association of Water Technologies.
  4. U.S. Army Corps of Engineers, EM 200-1-13, Minimizing the Risk of Legionellosis Associated with Building Water Systems.
  5. EPA Technologies for Legionella Control in Premise Plumbing Systems:  EPA 810-R-16-001 September 2016.
  6. ASHRAE Guideline 12-2000, Minimizing the Risk of Legionellosis Associated with Building Water Systems.
  7. ANSI/ASHRAE Standard 188-2018, Legionellosis: Risk Management for Building Water Systems.
  8. Cooling Technology Institute CTI WTB-148:  Legionellosis Guideline – Best Practices for Control of Legionella, July 2008.


Written by: Dominick Tuzzo


Please login or register to post comments.