In 1976, a mysterious and deadly flu-like illness plagued hundreds of individuals who had attended a meeting of the American Legion in Philadelphia. Of the 221 individuals who fell ill following the meeting, 34 died, prompting a large-scale investigation into the cause of the outbreak.

Several months later, scientists at the Centers for Disease Control and Prevention (CDC) identified the cause of the illness — a previously unknown bacterium, which they named Legionella. The investigation determined the bacteria had likely originated in the cooling tower effluent before being drawn into the building air intakes and spread throughout the ductwork.

Now, nearly 40 years later, Legionnaires’ disease and its milder form, Pontiac Fever, are still prevalent throughout the world and account for as many as 18,000 hospitalizations each year in the U.S. alone, according to the CDC.

To help battle Legionellosis, which includes both Legionnaires’ disease and Pontiac Fever, ASHRAE is currently developing Standard 188P: “Legionellosis: Risk Management for Building Water Systems.” The fourth public review draft of the standard is expected to be approved and made available for public comment soon.

Fighting a Microscopic Foe

While eradicating the bacteria — which can be found in cooling towers, evaporative condensers, potable water services, water heaters and storage tanks, and even decorative fountains and showers, among other places — is impossible, taking proper precautions can not only protect building occupants, but also protect the workers who routinely service the equipment.

“There are multiple standards around the world that attempt to address the issues,” said Standard 188P committee chair and professional engineer Tom Watson. “No consensus existed in the U.S. that a viable basis for a standard could be developed until the Standard 188P committee was formed.”

Watson also said the new standard builds on Guideline 12, “Minimizing the Risk of Legionellosis Associated with Building Water Systems,” as well as a 2007 World Health Organization document that promoted “Water Safety Plans” to address the risk of Legionnaires’ disease.

“ASHRAE thought that, while the industry knows how to manage the risk, a standardized practice was needed to specify for building managers [and] owners exactly what to do in their facilities in a systematic and scientifically sound way,” Watson said.

Scope of the Standard

Since the standard is still being developed, it is “premature” to discuss the details and content, though Watson said the standard will:

• Provide minimum Legionellosis risk management requirements for the design, construction, commission, operation, maintenance, repair, replacement, and expansion of new and existing buildings and their associated water systems and components;

• Apply to human-occupied commercial, institutional, multi-unit-residential, and industrial buildings, excluding single-family residential buildings. Only where specifically noted in the standard shall certain building water systems or parts of building water systems be exempt; and

• Be developed 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, commission, operation, maintenance, and service of centralized building water systems and components.

“We are optimistic this draft, which has been substantially rewritten from previous versions, will be made available soon,” Watson said. “Once the draft opens for public review, any interested party can comment on the proposed standard.”

Depending on the comments received, Watson said revisions will likely be made to further improve the standard, though, “without knowing the number of comments and the types of comments, accurately predicting a publication date is not feasible,” he said.

The Contractor’s Role

Even though the standard has not yet been published, many HVACR contractors are well aware of the risk that the Legionella bacterium poses and already take safety precautions when servicing equipment that may be contaminated with the bacteria.

“Over the years, we have found very few badly contaminated pieces of equipment,” said Ann Kahn, president of Kahn Mechanical Contractors in Dallas. “Since inhalation is the primary source of infection, when it is suspected in a specific piece of equipment, we take a couple of precautions. Masks are worn and ordinary bleach is used to kill the bacteria.”

Kahn said protecting her workers from the bacteria is just as important as protecting them from any other potential workplace hazards.

“I’m constantly concerned for the safety of all of our techs, all of the time. They encounter unsafe situations every day,” she said. “In that regard, Legionella bacteria cause the same concern as using ladders safely or using proper lock-out and tag-out procedures.”

While Greg Crumpton, owner of Airtight Mechanical in Charlotte, North Carolina, said his company is generally not involved in the water treatment aspect of maintenance and rarely, if ever, encounters the bacteria, he conceded that it is still a safety concern for the industry.

“As with all things that may reach up and bite you, education is the best measure for prevention,” Crumpton said. He added the industry has the ability to “create awareness without inciting fear and panic.”

Kahn agreed the industry has a responsibility to protect its own workers as well as its customers.

“We can sell our customers on keeping their equipment as clean as possible, and do the best job we can to fulfill that sale,” she said. “Prevention is our best hope with all diseases.”

Prevention is what Standard 188P hopes to accomplish, Watson said.

“The goal of the standard is to provide minimum Legionellosis risk management requirements that can be adopted or incorporated into codes and be used by building operators,” he said. “Effective design, maintenance, and operational procedures that avoid amplification and dissemination of Legionella are necessary throughout the life of a building to reduce the risk of the disease.”

To learn more about ASHRAE Standard 188P, visit

Publication date: 9/29/2014

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