Cooling towers may look like they’re just another piece of equipment—humming away to help keep your facility comfortable. But what if, hidden inside the cooling tower, there’s a threat that could negatively impact your facility and the health of those around it?

Within weeks, up to 221 people were symptomatic, and 34 expired from the illness. Physicians and public health officials first thought they were dealing with a traditional form of pneumonia, but standard treatments didn’t work. CDC microbiologists identified the cause in January, 1977 — a previously unknown bacterium coined Legionella pneumophila. Water samples from the hotel’s cooling tower, a device used to cool water for the HVAC system, identified the presence of the bacteria. The hypothesis was that those who had come down with the illness had been exposed to contaminated mists from the cooling tower. This meant that other cooling towers or water systems could be contaminated with the bacteria, and the threat was as real to buildings in Los Angeles as to those in Philadelphia.

The following FAQs provide our response to common questions about Legionnaires’ disease, so-named after the American Legion Convention and the Legionnaires’ who became ill at the convention, and Legionella bacteria. Our aim is to give building owners and managers actionable tips on how to prevent Legionella contamination on their properties and protect their occupants from Legionnaires’ disease.

Are Cooling Towers a Risk for Legionella?

Yes, cooling towers can be a risk for Legionella growth, especially if they’re not well-maintained. Legionella bacteria thrive in warm water and can spread through aerosolized water droplets. When cooling towers release these droplets into the surrounding air, people who inhale them could be exposed to the bacteria that causes Legionnaires’ disease.

Current guidance indicates that all facilities that operate cooling towers should conduct formal evaluations to identify areas prone to bacterial growth and ensure compliance with cooling tower regulations.

Remember, too, that OSHA Legionella cooling tower guidelines stress regular inspections and proper treatment as critical components of workplace safety.

Note:

• Legionella threats increase when cooling towers are not maintained properly
• There can be potential for Legionella to grow in cooling towers even when normal treatment programs are in place

How Does Legionella Get into Cooling Towers?

Legionella bacteria naturally occur in low concentrations in lakes, rivers, and groundwater. They can enter a building’s water system through municipal supplies or other water sources, such as seeding from other nearby cooling towers or decorative fountains, and eventually find their way into cooling towers.

It is in the cooling tower where factors like inadequate Legionella cooling tower water treatment, warm temperatures, and stagnant water can fuel bacterial growth.

Note:

• Warm, stagnant water fosters Legionella
• Poor cooling tower Legionella control or faulty design can increase the risk
• Cooling towers should be routinely monitored and maintained to reduce the potential for amplification

Can You Get Legionnaires’ Disease from a Cooling Tower?

Yes, cooling towers can be a source of Legionnaires’ disease. Exposure to Legionella occurs by inhaling water droplets containing Legionella bacteria, which can be dispersed by cooling towers.

Outbreaks have occurred when a contaminated tower dispersed water aerosols containing Legionella bacteria over a wide area. While not extremely common, these incidents underscore the importance of cooling tower Legionella maintenance and testing procedures.

Note:

• High-risk groups include older adults, smokers, and those with weakened immune systems.
• The disease spreads via contaminated droplets, not person-to-person.
• Adhering to cooling tower guidelines for maintenance and testing helps protect the public.

How Do You Control Legionella in a Cooling Tower?

Effective cooling tower Legionella control revolves around a solid water management plan that typically includes:

• Routine Cleaning: Removal of scale, sediment, and biofilms Biocide Treatment: Regular use of chemicals (e.g., chlorine, bromine) to inhibit bacterial growth
• System Inspections: Checking water temperature, biocide residual, pH, and overall tower condition
• Preventive Maintenance: Ensuring good water flow, prevent areas of stagnation, and maintain proper cooling tower function

FACS can help you establish a cooling tower maintenance plan.

What Are Acceptable Levels of Legionella in Cooling Towers?

Various regulatory agencies and scientific organizations worldwide set different thresholds for Legionella levels in cooling towers, but a common stance is that any detectable level may warrant additional monitoring or corrective action, depending on cooling tower requirements in your area. Some guidelines categorize Legionella concentrations (CFU/mL) to determine the urgency of corrective actions, such as disinfection.

ASHRAE Standard 188-2021 is one voluntary standard that outlines risk management strategies in the United States. The Centers for Disease Control and Prevention has also published a toolkit which outlines a multi-factorial approach to Legionella sample interpretation. The American Industrial Hygiene Association (AIHA) has published comprehensive guidelines on controls and Legionella risk assessment and sample interpretation. OSHA references also emphasize the importance of immediate remediation if Legionella is detected at higher-than-acceptable levels.

How Do You Test for Legionella in a Cooling Tower?

Cooling tower Legionella testing requirements can vary by region, but common methods of testing include:

• Culture Testing (ISO 11731): Growing Legionella in a lab from water samples
• PCR (Polymerase Chain Reaction): DNA-based detection methods which can be useful for faster negative screening, but do not distinguish between live and dead bacteria

Ongoing testing allows facility managers to track the effectiveness of Legionella cooling tower water treatment programs and keep the facility safe from a Legionella outbreak.

How Often Should a Cooling Tower Be Tested for Legionella?

Frequency may depend on local cooling tower regulations, if any, and the specific risk profile of the building or industrial site. While quarterly testing is common, some high-risk facilities—such as hospitals—may opt for monthly checks. More frequent testing helps catch issues early, reducing the chance of an outbreak.

FACS can help you establish an optimum testing and maintenance program for Legionella. Get our environmental health experts on your side.

How Can Legionnaires’ Disease Be Prevented in Cooling Towers?

Prevention hinges on proactive cooling tower Legionella control, which includes:

• Water Management Plan Implementation: Ensuring risk factors are identified, controlled, and monitored to discourage bacterial growth.
• Cleaning and Descaling: Removing layers of scale or biofilm that can harbor bacteria.
• Biocides and Disinfectants: Using approved chemicals, sometimes in rotation, to minimize bacterial growth.
• System Design Improvements: Eliminating stagnant water zones, preventing aerosol drift, and optimizing water flow.

When facility managers follow best practices, they not only comply with cooling tower regulations and guidelines but also significantly reduce health risks from Legionella.

What Are the Symptoms of Legionnaires’ Disease?

The common symptoms of Legionella include fever, chills, cough, muscle aches, and headaches. However, always consult a healthcare professional for any medical concerns.

Do I Need a Professional Consultant for Legionella Control?

While in-house teams can manage basic upkeep, a consultant or water treatment specialist may be necessary for a thorough cooling tower Legionella risk assessment or after a known or suspected outbreak. This ensures robust compliance with cooling tower Legionella testing requirements and local regulations.

For more information, contact FACS. We can help you and your team make Legionella concerns something your maintenance team has well under control.

For help selecting the most effective prevention strategies and to ensure your Legionella water management plan protects your property adequately, be sure to contact FACS by telephone here: 888-711-9998.