Home Featured Continuous Airborne Legionella Detection Reduces HVAC Health Risk

Continuous Airborne Legionella Detection Reduces HVAC Health Risk

Continuous Airborne Legionella Detection Reduces HVAC Health Risk

Continuous Airborne Legionella Detection Reduces HVAC Health RiskTo safeguard the health of building occupants, nearby personnel and even individuals innocently passing nearby, HVAC professionals that install chiller systems with cooling towers are seeking solutions that reduce the chance of spreading the potentially deadly Legionella bacteria that causes Legionnaires’ disease.

Legionnaires’ Disease in HVAC Systems

Legionnaires’ disease is a severe, even fatal, form of pneumonia caused by the bacteria. According to the Centers for Disease Control and Prevention (CDC), 6,000 annual cases of Legionnaires’ disease were reported in the United States, with one out of 10 dying.

Although Legionella is found naturally in bodies of water and in the majority of building water systems, the highest risk is when the bacteria becomes airborne in mist, spray or droplets that can be breathed into the lungs.

This is where cooling towers play a critical role. In HVAC, cooling towers are often used in conjunction with chillers for large building cooling systems. A recent CDC study involving 196 cooling towers nationwide found that 84 percent contained Legionella DNA in the water.

The problem is that cooling towers by their very nature use evaporative methods to rapidly cool the water in the system. This can cause “drift” – a fine mist – that can travel long distances based on wind speed, building height, and cooling tower location.

For buildings where cooling towers are installed on roofs in nearby vicinity of fresh air intake systems – as is often the case – this could expose the building’s occupants to the bacteria. It can also pose a risk to nearby building personnel conducting maintenance.

When drift is considerable, it can affect individuals in nearby buildings, parking lots and even on the street as well. Reports show that airborne Legionella can travel as far as one mile in some instances.

Such was the case in recent national news that Disneyland had to shut down two cooling towers, located over 100 feet from areas accessible to guests that were ultimately found to have Legionella. According to the L.A. Times, in the Legionnaires’ disease outbreak, 11 of 15 people infected had visited the park, and four had not – including two that died.

These, and other incidents, are serving as a wakeup call for HVAC industry professionals that utilize cooling towers with chillers.

Continuous Monitoring for Airborne Legionella

Today simple, economical, automated systems can provide continuous monitoring for airborne Legionella. Automatic notification to cloud networks and mobile devices warn of initial detection of the bacteria, followed by full confirmation in a matter of hours.

This stands in stark contrast to the days or even weeks shipping samples to off-site labs before receiving results.

Current testing methods typically involve infrequent (i.e. monthly or quarterly) tests using settle plates that contain culture media exposed to the air that are then incubated or impactors that must be sent to a third party lab for analysis. For these types of tests, it can be three days before the results are available.

Tests are also often performed on the water itself, which can demonstrate the presence of Legionella but not determine if there is any airborne risk.

Instead, continuous monitoring devices such as PathogenAlert’s RAPID (Rapid Airborne Pathogen Identification and Detection) Reader System can detect and confirm the presence of airborne Legionella within hours of sampling.

The small wireless device mounts anywhere and operates by automatically sampling the air in cooling towers, chillers, ducts, or other high risk areas every five minutes (or any other time frame specified) on a 24/7 basis. Air is drawn in and flows across the cartridge, allowing any Legionella microbes to settle on a nutrient rich site where it then begins to grow.

To detect pathogen growth, the device uses optical measurement and laser technology, along with electronic digital signal processing. Inhibitors are utilized to eliminate false readings. Detection software also monitors for erratic behavior that can be caused by non-pathogenic particles, such as dust, and compensates appropriately.

The RAPID Reader can be mounted just about anywhere, including on cooling towers, inside building ductwork or anywhere in occupied areas. Up to 25 sensors can be connected to a single base station with each sensor covering roughly 2,500 square feet.

The cloud-based platform allows continuous, remote online monitoring of individual or multiple locations from a laptop “dashboard” that consolidates key data for review. Alarms and notifications can be sent to any mobile device.

Early Detection = Early Remediation

One of the primary goals of early detection is to allow existing and affective techniques to be implemented as quickly as possible to destroy Legionella bacteria.

Traditional methods are water chemicals and disinfectants. Unfortunately, these methods are ineffective against Legionella that is already in the air.

There are, however, other options. Germicidal UV light systems destroy Legionella in seconds. At a specific wavelength, UV-C deactivates the DNA of bacteria, viruses, and other pathogens, which eliminates its ability to multiply and cause disease. This tool when bundled with automated airborne legionella sensors, are effective seek-and-destroy tools for the remediation of Legionella.

With airborne Legionella and cooling towers still making news headlines together, it is time for HVAC professionals to look into automated testing and treatment options that can identify and handle the problem before it becomes a news generating event.

For more information, visit www.pathogenalert.com.



In New York City, a series of deadly outbreaks of Legionnaires Disease has become an all too common occurrence. Over the last few years, hundreds have been severely sickened and dozens killed by deadly bacteria that proliferates in water systems like the cooling towers used in conjunction with large HVAC systems.

So, when a cooling tower supporting the HVAC system at NYC Health + Hospitals/Lincoln was nearing its expected end of life, the management of the 362-bed hospital in the South Bronx saw an opportunity. The year before, the neighboring community had experienced outbreaks of Legionnaires’ disease, and even though the hospital’s cooling towers played no role in those outbreaks, the chance to increase protections against possible future exposures of the bacteria that cause the disease was an important consideration.

Accordingly, the hospital’s engineering and management teams prioritized the selection of an anti-microbial cooling tower option. They also gave extra weight to finding a system that would save energy, consistent with the larger health system’s ongoing goals.

Finding the Source

Legionnaires’ disease is a severe form of lung infection caused by exposure to bacteria known as Legionella. Found naturally in freshwater environments like lakes and streams, Legionella becomes a health hazard when it grows unabated in water that is not properly treated. While this can include showerheads, hot tubs and hot water heaters, cooling towers are often found to be the source of outbreaks.

Cooling towers have a long history of effectively expelling heat from the water used in many commercial and industrial applications. However, a recent study from the Center for Disease Control and Prevention (CDC) found that an overwhelming majority of the cooling towers they tested contained Legionella DNA. This indicates that the dangerous bacteria was either currently present or had been at some point, and without proper precautions would eventually give rise to an outbreak.

Legionella bacteria can flourish in cooling towers and spread to humans when expelled water vapor or mist containing the bacteria is inhaled.

Addressing Microbial Concerns


NYC Health + Hospitals/Lincoln, a large, full-service community medical center and teaching hospital – part of the largest public health care system in the U.S. – knew what was needed. Louis Iglhaut, associate executive director at NYC Health + Hospitals, led the team responsible for the specification, acquisition, and installation of the new cooling towers.

Originally, one of Iglhaut’s primary design priorities for Lincoln Hospital’s new cooling tower was to focus on efficient and thorough water circulation. In other words, the design of the new towers should not have corners in the basin, as many do, including the stainless steel models the hospital was replacing.


“We needed to think outside the box,” explains Iglhaut. “Given our concern about the dangers of microbial growth, we decided to only considering towers with rounded basins.

Iglhault’s search for a superior design lead his team to find a new breed of cooling towers that had just recently become available. Fully-compounded with an anti-microbial resin, these advanced technology towers contain wide-spectrum additives that operate on a cellular level to continuously disrupt and prevent uncontrolled growth of microorganisms and biofilm.

“These towers, which are rounded, not only solved the circulation problem but also have anti-microbial chemicals embedded into the tower’s HDPE material, which helps to prevent the growth of dangerous bacteria such as Legionella,” he says.

The towers the hospital selected were made by Delta Cooling Towers, which introduced the HDPE (high-density polyethylene) cooling tower in the 1970s.

While some cooling tower manufacturers now market a tower with an anti-microbial fill (the medium over which the hot water is distributed as it is being cooled), a vastly better option is to have a cooling tower featuring the fill, structural casing, and sump all composed of anti-microbial material.

This is highly significant because biofilm growth and microorganisms allow a place for bacteria to hide from chemical treatments and also provide nutrients for pathogen growth.

Convinced that the rounded design, HDPE durability and protective features of the anti-microbial material were a good solution for Lincoln Hospital, the procurement team selected Delta’s Anti-Microbial TM Series model with 18 modular cooling towers that provide a combined total of 6,000 cooling tons.

Corrosion and Chemical Concerns

To reduce future outbreaks, cities like New York are increasingly requiring extensive use of harsh chemicals to be used within all cooling towers. For Lincoln Hospital, this requires a professionally maintained water treatment program that uses strong biocides and acid feed treatment chemicals. While these could have a life-shortening corrosive effect on even stainless steel towers, engineered plastic HDPE towers can withstand even the harshest chemicals.

“I think that the corrosion resistance of these HDPE towers is demonstrated by the manufacturer’s 20-year warranty,” Iglhaut says.

Significant energy savings

Another major factor affecting Lincoln Hospital’s decision to adopt the new Delta cooling towers was the promise of substantial energy savings. New York City Health + Hospitals was well aware of the city’s mandate to save on energy, so it teamed up with the country’s largest state power organization, dedicated to innovative and energy-efficient infrastructure.

“We worked with New York Power Authority to ensure that the new cooling towers would be as energy-efficient as possible,” Iglhaut says. “Our old towers used large, 30-horsepower fans on each unit, which required the use of a lot of electric power. The new modular units are equipped with smaller horsepower, 60-inch fans, so the energy consumption is far less,” he says.

“Also, we have installed VFDs (variable-frequency drives), which will give us even more savings. The total electric power energy savings calculated by our engineering firm was figured at about 40 percent, which is quite an accomplishment.”

Iglhaut adds that even the installation of the new cooling towers added to efficiencies. Because the towers were smaller and lighter, the installation team was able to use a small crane to lift the towers into position, which ensures a seamless transition from the old system to the new one.

“Sometimes I think people like engineers should be judged by things that don’t happen in the hospital.” He says. “In this case, the cooling towers went in seamlessly without interruptions to any patient areas. It was up and running with zero downtime.”

For more information, visit www.deltacooling.com.