Legionnaires Disease and Infection Control

              Legionnaires disease is a severe form of pneumonia, consisting of lung inflammation brought on by airborne-based infection. The disease is the direct cause of bacterium known as legionella. This bacterium cannot be transferred from person-to-person contact, but rather through inhalation. Typically, those with weakened immune systems are far more susceptible to Legionnaires disease. This includes smokers, seniors, and those with pre-existing lung conditions such as asthma. The question, however, is how to prevent Legionnaires disease in the first place? As it turns out, humidity control and system maintenance play a major role in reducing airborne infection risk potentialities. In this long-form blog, we will explore the symptoms of Legionnaires disease, examine how to curb airborne infection potentialities and healthcare-associated infections with maximum humidity control, and discuss how humidity control influences airborne infection risk.


              Legionnaires disease is known to typically develop between 2-10 days after the host has been exposed to legionella bacteria. Initial warning signs come in the form of symptoms such as headaches, muscle pain, chills, and fevers at 104 F or higher. Other symptoms will become prevalent by the second or third day, which may include mucus or blood-laced coughing, shortness of breath, chest pains, gastrointestinal issues resulting in nausea, vomiting and/or diarrhea, and even confusion or a loss of equilibrium. Infections in wounds and organs such as the heart are also possibilities in rare circumstances. Fatalities are completely possible as a direct result of healthcare-associated infections or other methods of contracting Legionella bacteria.

              How Humidity Control Influences Airborne Infection Risk

              Airborne infection control and Legionnaires disease can impact an environment in different ways, and this begins with our own influence from a microscopic level. Human beings produce a profound number of airborne bacteria without even knowing it. Our bodies are capable of producing and releasing microscopic water droplets known as aerosols. Consisting of 97% water and 3% solutes (such as salts, proteins, and similar substances), they can easily retain harmful bacteria within their mass. How humidity control influences airborne infection risk is evident when examining the dryness of conditions themselves. In environments with low relative humidity (below 40% RH), such microbes are able to float more freely through the airspace since, in dry atmospheres, aerosols are subjected to evaporation and quickly lose moisture mass. These droplets, therefore, reduce in size, making them lighter. Occupants of the same space are at a far greater risk of becoming infected and developing health issues in these circumstances. The connection between airborne infection control and Legionnaires disease also extends to the fact that Legionnaires disease is lung-based. Therefore, it thrives much in the same manner as asthmatic and allergic triggers do, as the nasal passages are unable to retain sufficient moisture in drier environments with low relative humidity.

              Healthcare-Associated Infections

              Legionnaires disease is a threat in healthcare applications that handle massive quantities of different strains of bacteria, such as retirement residences, hospitals, laboratories, etc.. Like other airborne-based infections, Legionnaires disease relies on inadequately humidified air as a means of transference from person to person via inhalation of infectious microbes. Healthcare-associated infections are a major focus of application operators, and great analytic strides have been made in recent years to reduce the risk, regarding everything from structural analysis to psychrometric evaluation.

              Effects of Humidity on Microbiological Risk Reduction

              Legionella is an aerobe, (needs Oxygen) requires L-cysteine (a common amino acid), and a relatively high iron content in water to be able to multiply. Conditions adequately humidified with 40% to 60% RH on a regular basis offer a far safer environment with reduced potentialities of occupants developing Legionnaires disease, as sufficient air hydration behaves much like a protective barrier. Aerosols and their subsequent microbes fall and settle more quickly, dramatically reducing the reach of airborne-based bacteria. This reduces healthcare-associated infections and can protect those with weakened immune systems from contracting Legionnaires disease; particularly as healthcare environments are primarily occupied by those with respiratory issues and illnesses. When factoring in the relationship between low-humidity conditions and viral infection potentialities, it becomes clear that maintaining consistently balanced relative humidity (RH) levels in any environment is essential. The dissolved salts within any remaining droplets also work to eliminate leftover microbes in aerosols, which reduces the risk of infection as well. The effects of humidity on microbiological risk reduction are profound, to say the least.

              Pathogenic bacteria (Disease-causing bacteria)

              • Legionella pneumophilla
              • Aeromonas hydrophila
              • Pseudomonas aeruginosa
              • Listeria monocytogenes
              • Amoebas, protozoa

              Even though pathogenic bacteria are not supposed to be in drinking water or entering into building systems, they can still be found in low numbers, so the growth of these must be prevented or at least limited to ensure a safe and healthy system. To minimize the growth of bacteria, it is necessary to maintain a high level of hygiene in your entire HVAC system including the humidifier.

              Endotoxins in the Air

              When bacteria are treated and die, they release endotoxins from their cells. Endotoxins in the air are harmful to people as they can cause serious diseases. When an evaporative cooling system is turned off, the media dries out, and as a result, some or most of the living organisms on the surface will die and release endotoxins into the air. During disinfection of a system, endotoxins are also released into the water. In other words, the cleaner the water is, the lower the content of released endotoxins there is in the air. This is the same with mist eliminators from HPM systems – if excess water is recycled back to tanks, the entire system will be contaminated.

              Reverse Osmosis System

              In many Condair humidification systems, a reverse osmosis (RO) system is implemented to remove total dissolved solids from the water and filter away any microorganisms which are present. Generally, RO systems are also an effective hygiene barrier. They will remove around 98% of all microorganisms entering into the water treatment system, as well as removew the trace elements and most nutrients desired by bacteria. As an example, Legionella pneumophila needs a high content of iron in the water to be able to multiply. When 98% of the iron content is removed in RO, the growth of Legionella will be minimized accordingly, and the risk of occupants of an environment developing Legionnaires disease is greatly reduced. However, RO systems also have to be kept fresh. These systems should be operated at minimum once every day to ensure proper hygiene in the system itself and to ensure no biofilm build up in the system.

              Ways Adiabatic Cooling Reduces Legionellosis Risk

              When these systems are designed in a correct way, the risk of having aerosols in the air is significantly lower compared to high pressure misting systems. Water evaporates into the air, the direct result of the air passing through the media and into vapor form. Only when air velocity is too high, there is a risk for aerosols that can contain bacteria. Hygiene is another one of the ways adiabatic cooling reduces Legionellosis risk, in that a clean system is incredibly efficient. Proper hygiene and cleanliness helps avoid the fouling on the surfaces of system media, which may result in the increased pressure drop and reduced efficiency. If biofilm builds up in tanks and pipes, this can present risks for people during service and maintenance of the system, or those who inhabit an indoor environment when the system is in operation. If the wash over water from the evaporative pads is contaminated, and this water is recycled back to tanks, the entire systems is at risk of contamination if necessary measures are not taken. Condair is proud of the many ways adiabatic cooling reduces Legionellosis risk, as our products are carefully engineered to minimize required maintenance without putting any occupants at risk. Infection control remains consistent and, in fact, much more effective.

              The effects of humidity on microbiological risk reduction are incredible, but you won’t see results if your humidification systems are not kept in working order. Around 70 % of the body mass of bacteria is water. When waterborne bacteria are removed from their normal environment, where they have full access to water, they become stressed. If the bacteria dry out from a lack of moisture in the environment, they will die, or at least not be able to continue growing. Emptying of sumps under evaporative media, and drying out the media once a day, will reduce fouling (biofilm and dust) on the media. Sections of the adiabatic system that aren’t needed for cooling or humidifying should be kept dry if possible. It is well known that the cooling demands vary over the year, so if there are periods with limited need, a control strategy should be implemented. This will allow a minimized section to operate in an optimized way, with excess water, and the rest of the system should be kept dry. This, however, requires that the piping to the evaporative media be constructed in a way so that pipes can be flushed without wetting the media. Condair ensures implementation of this feature with all modern humidification systems in order to better protect inhabitants against Legionnaires disease contracted through the air, regardless of whether via healthcare-associated infections or other means of airborne transference.

              New ASHRAE Standards Maximize Infection Control Efficiency

              After 10 years of work, ASHRAE has now released a new standard, ASHRAE 188-2015 Legionellosis: Risk Management for Building Water Systems. The intention of this standard is to prevent the risk for Legionellosis from water systems in any building, new or existing. With this new standard now implemented, manufacturers of humidification systems are required to ensure that inhabitants are effectively protected against infection from harmful microbes that could lead to illnesses such as Legionnaires disease. Such measures help to increase infection control exponentially. Condair’s humidification systems are a leading example of how to prevent Legionnaires disease, as such highly efficient systems are built not only in accordance with new ASHRAE standards but to exceed their requirements to further protect those with weakened immune systems.

              Condair specializes in the design and production of superior humidification systems. We create the most appropriate solutions to meet your specific needs in the most efficient and cost-effective way. To this end, we draw upon our extensive experience to develop an ever-growing range of products manufactured to our stringent ISO 9001:2000 certified quality standards that will provide our customers with maximum reliability, minimum maintenance and a choice of energy sources. When you choose Condair, you are choosing the company that has built a reputation for superior quality humidification systems. For absolute airborne infection control and Legionnaires disease risk management, we offer the ideal solution. Contact Condair today to learn more about our humidification solutions – and the steps we take and suggestions we can give on how to prevent Legionnaires disease.


              Contact us today to learn how to prevent Legionnaires disease.