Phigenics, LLC

ASHRAE standard 188P update prevention of legionellosis associated with building water systems


Source: Phigenics, LLC

Public Review Period June 10-July 25, 2011

The American Society of Heating, Refrigerating and Air-conditioning Engineers (ASHRAE) has developed a proposed Standard Practice that specifies what is required to prevent legionellosis associated with building water systems. The proposed Standard Practice was approved in July 2010 for public review publication. The first public review was completed in November 2010; there were many supportive comments posted and also many excellent suggestions to improve the Standard. A revision was produced in response to comments received during the public review. The second public review will begin June 10, 2011.


The American Society of Heating, Refrigerating and Air-conditioning Engineers (ASHRAE) develops the following three types of Standards in accordance with the American National Standards Institute (ANSI) rules and regulations: 1) Method of Measurement or Test, 2) Standard Design and 3) Standard Practice.

The ASHRAE Standard 188P is a Standard Practice.

A summary of the Standard Practice is:

Compliance with this Standard Practice requires that facility managers/owners establish a team with assigned responsibilities and accountabilities. The first job for the team is to describe for each facility how water is processed and used in the facility; this description must be schematically represented in process flow diagrams. Each processing step must be named and numbered on the diagrams. Next, the team is required to perform systematic hazard analysis to 1) identify the potential hazards for each step in the process, 2) decide if the risk of those hazards is significant (yes or no), and if “yes,” 3) determine what hazard control is being applied or could be applied at that processing step. Every step in the process at which hazard control is applied must be designated a critical control point. For every critical control point, the team must address four issues about the hazard control method applied: (1) the critical control limit, (2) the hazard control monitoring method, (3) the frequency of monitoring the hazard control and (4) the corrective actions to be taken if the critical control limit is violated. Lastly, the team must decide how it will confirm that the overall plan is being implemented (verification) and provide evidence that the plan is effective (validation).


Essentially all cases of legionellosis are associated with building water systems.

The cause of the disease and how to prevent it have been known for thirty years. In the US, government or professional organizations have published many technical guidance documents about how to analyze and control the cause of the problem. Most of these publications have been widely available at no cost for well over a decade.

An example of one such guidance document is from the Association of Water Technologies published in 2003; it provides excellent specific technical guidance for how to control Legionella in cooling towers, potable water systems and gives further specific guidance for healthcare building water systems. It has been widely referenced and has been easily accessible at no cost for almost a decade.

Internationally, there is a vast body of specific technical information rich in detail that documents how to analyze and control Legionella in all relevant types of building water systems. An excellent compilation of this guidance is published by the World Health Organization and is available as a free download.

There is overwhelming evidence that control of Legionella can be achieved in all types of building water systems. Readily available, practical, technical guidance specifically instructs how to control Legionella and provides references that document successful applications. Site-specific considerations are necessary because a “one-size-fits-all” remedy could never account for all the variations encountered in building water systems. These technical guidance publications reference much of the scientific literature that documents successful real-world applications; the aforementioned full-length book is an excellent example of such a publication and there is easy access to many others.

So, really, there is no mystery about how to analyze and control Legionella in building water systems.

And yet, estimates are that every year another 4,000 people in the US will die from legionellosis and there will be an estimated 25,000 new cases.

The number of legionellosis outbreaks in the US has now surpassed the number of waterborne outbreaks of gastrointestinal disease. Legionella, according to the CDC, causes the majority waterborne disease outbreaks associated with building water systems which are those outbreaks occurring outside the jurisdiction of US public water utilities.

The number of serious or lethal infections that have occurred since scientists and engineers worked out the cause and how to prevent legionellosis is astonishing. And so have been the costs.

Of the three leading causes of waterborne disease outbreaks in the US, legionellosis accounts for the largest direct healthcare dollar cost, eclipsing the costs due to other waterborne disease outbreaks. Inpatient hospitalization costs per case averaged more than $34,000 for Legionnaires' disease in the US and the annual direct healthcare cost of legionellosis is probably more than several hundred million dollars.

But the indirect cost of legionellosis in the US is far greater that that. Since many Legionella infections result in severe pneumonia, data for indirect cost estimates of community-acquired pneumonia (CAP) are relevant. For every direct healthcare dollar spent on CAP, about $12 of indirect cost is incurred due to lost productivity, absenteeism and disability. Therefore, the annual cost of the many thousands of legionellosis cases associated with building water systems may well be counted in the billions of dollars.

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