Air Conditioning and Legionella and Bacteria
Introduction
Air conditioning (AC) is a fundamental utility that keeps businesses running, operations productive and people comfortable. From offices and manufacturing plants to healthcare facilities and data centres, reliable temperature control is crucial for everyday life and critical processes. Yet, amidst the hum of efficiency, there’s an often-overlooked aspect of these systems: their potential to harbour microbial growth, including bacteria like Legionella.
At Aggreko, we understand that efficiency extends beyond just cooling. It encompasses the safety and well-being of your environment. We’re committed to providing safe and efficient permanent and temporary temperature control solutions that empower your operations without compromise.
In this guide, we’ll discuss the connection between air conditioning and bacteria, address common misconceptions and equip you with the knowledge to proactively prevent risks and maintain a healthy atmosphere.
Bacteria in Air Conditioning Units
While the primary function of an air conditioning system is to regulate temperature, its very design can, under certain conditions, create environments where various microorganisms thrive.
Air conditioning systems involve the movement of air, the condensation of moisture and the presence of various surfaces like filters, coils and ductwork. These elements can become prime breeding grounds for a range of bacteria and mould. Over time, dust, debris and airborne particles accumulate on filters and coils.
When combined with the moisture generated during the cooling process, these areas can become damp and provide the nutrients microorganisms need to grow. If these conditions persist, mould spores can germinate, and various bacterial colonies can establish themselves.
Several factors can contribute to this microbial buildup:
- Moisture and condensation: inadequate drainage of condensation or persistent humidity within the system creates a damp environment.
- Stagnant water: water left in drain pans or uncleaned components provides a perfect breeding ground.
- Poor maintenance: infrequent cleaning or replacement of air filters, coils and ducts allows contaminants to accumulate and grow.
- Inadequate ventilation: poor airflow can lead to pockets of stale, humid air within the system, further encouraging microbial development.
While these microorganisms multiply within the air conditioning system, they can become airborne and circulate throughout the conditioned space. Inhalation of mould spores or bacteria can lead to health issues for occupants. These can include:
- Respiratory problems: worsening of asthma symptoms, bronchitis or other respiratory irritations.
- Allergies: triggering allergic reactions with symptoms like sneezing, coughing, watery eyes and skin rashes.
- Sick Building Syndrome (SBS): a range of non-specific symptoms such as headaches, dizziness and respiratory irritation that appear to be linked to time spent in a building, often improving after leaving the building. While complex, poor indoor air quality, often exacerbated by contaminated HVAC systems, is a key contributing factor.
It's important to note that bacteria from air conditioning can cause discomfort and health issues. The specific public health concern around Legionella is typically associated with water-based systems that can produce fine, inhalable aerosols. This distinction is crucial: while all air conditioning systems benefit from cleanliness to prevent general microbial growth, the risk of Legionella in air conditioning is more specifically tied to the management of water within certain types of units, particularly large commercial and industrial installations.
What is Legionella?
Legionella is a genus of bacteria commonly found in natural freshwater environments. However, when it finds its way into artificial water systems, it can multiply to dangerous levels. The most severe illness is Legionnaires’ disease, a potentially fatal form of pneumonia. There’s also a milder, flu-like illness called Pontiac fever, caused by the same bacteria but without pneumonia.
How Legionella Spreads
Unlike other airborne pathogens that might spread through dry dust, Legionella thrives in warm, stagnant water. It does not spread from person to person. Instead, the infection occurs when microscopic water droplets or mist contaminated with the bacteria are inhaled deep into the lungs.
Can You Get Legionella from Air Conditioning?
This depends on the type of air conditioning system and its use of water. Standard residential or vehicle air conditioning units that cool air by circulating refrigerants and simply dehumidify the air are generally not a source of Legionella. They do not create the large volumes of stagnant water or fine aerosols necessary for the bacteria to thrive and spread.
The primary concern for Legionella in air conditioning systems lies with larger, complex commercial and industrial installations that incorporate water-based components. This includes:
- Cooling towers: these are large heat rejection devices that cool water by evaporating a small portion of it into the atmosphere, creating a perfect environment for aerosol generation if not properly maintained.
- Evaporative condensers: like cooling towers, these also use water evaporation for cooling.
- Humidifiers: especially those that use a cold-water supply to create a fine mist for humidity control.
- Other water features or plumbing systems associated with the HVAC infrastructure that can generate inhalable aerosols.
Cooling towers are the most common source of Legionella outbreaks linked to HVAC systems. They provide ideal conditions – warm, recirculating water and fine mist – that, without strict maintenance, can spread contaminated aerosols across large areas.
It’s a common misconception that Legionella in air conditioning arises from the dry, cooled air discharged from typical vents. The risk is not from the cooled air itself, but from the water systems within or connected to the AC infrastructure that can become contaminated and then release fine, bacterium-laden water droplets into the air.
Symptoms of Legionnaires’ Disease and Pontiac Fever
If someone has been exposed to Legionella, symptoms typically begin two to 10 days after exposure.
Legionnaires’ disease presents as a severe form of pneumonia with symptoms including:
- High fever
- Chills
- Muscle aches
- Headache
- Fatigue
- A cough (which can be dry or produce sputum)
- Shortness of breath
Gastrointestinal symptoms like nausea, vomiting and diarrhoea can also occur, and in severe cases, it can affect the nervous system. For more information on the symptoms of Legionnaires’ disease, visit the NHS website.
Pontiac fever is a milder, flu-like illness with symptoms such as fever, chills, headache and muscle aches. It does not cause pneumonia and usually resolves on its own within a few days.
How to Ensure Air Quality and Safety
The presence of bacteria in air conditioning units might seem daunting, but these risks are largely preventable through diligent maintenance and proactive management. Implementing a strategy for responsible facility management will safeguard health and operational continuity.
This is particularly important for cooling towers, where poor water treatment or stagnant conditions can allow Legionella to multiply. Strict water management is the frontline defence.
Here are the key preventative strategies businesses should adopt:
- Routinely clean or replace air filters. Clogged filters reduce the efficiency of AC units and become breeding grounds for mould and bacteria.
- Ensure evaporator and condenser coils are clean and free of dirt and debris. Check that condensation drain pans are clean, free-flowing and not allowing water to sit and stagnate.
- Periodically inspect and clean air ducts to remove accumulated dust, mould and other contaminants that can be circulated throughout the building.
- For systems involving water, maintain water temperatures outside the optimal growth range for Legionella. This means keeping cold water below 20°C and hot water above 50°C, with thermostatic mixer valves where necessary to prevent scalding at outlets.
- Eliminate “dead legs” (unused sections of pipework) where water can sit idle and become stagnant by ensuring infrequently used outlets are flushed regularly.
- Implement appropriate water treatment programmes, which may include biocides or other disinfection methods, to control microbial growth in water circuits.
- Ensure proper and consistent airflow throughout your building. Good ventilation helps to reduce overall indoor humidity levels, making it less conducive for mould and bacteria to thrive.
- Monitor and control humidity within your conditioned spaces, as excessively high humidity can encourage microbial growth even on surfaces not directly within the AC system.
- Hiring temporary air conditioning can allow for thorough servicing of permanent systems, reducing downtime and enabling urgent repairs without disrupting operations or compromising climate control.
- Regular inspections and servicing by qualified, experienced technicians are important. These professionals can identify potential issues, assess system integrity and perform thorough cleaning and necessary repairs beyond what in-house teams might handle.
- For systems at risk of Legionella, specialised risk assessments and testing should be conducted periodically to monitor water quality and bacteria counts, ensuring compliance and peace of mind.
- Consider the integration of advanced solutions like UV-C lights within air handling units or ductwork. UV light can effectively kill airborne microorganisms, including bacteria and mould, by disrupting their DNA.
- Applying antimicrobial coatings to internal components can inhibit bacterial and fungal growth on surfaces within the system.
By integrating these proactive measures, businesses can significantly reduce the potential for bacteria in air conditioning units and effectively mitigate the risk of Legionella, ensuring a healthier and safer environment for everyone.
Compliance and Regulatory Frameworks
Businesses, particularly those operating larger facilities, must also be aware of and comply with relevant regulatory guidelines. In the UK, for instance, the Health and Safety Executive’s (HSE) Approved Code of Practice (ACoP) L8 and its associated technical guidance (HSG274) provide clear requirements for controlling Legionella risks in water systems, including those associated with air conditioning systems.
These regulations place particular focus on cooling towers, which have historically been the source of many workplace-related Legionella outbreaks. Adhering to these guidelines is a legal obligation and a critical component of risk management.
Aggreko’s Commitment to Safe and Efficient Environments
At Aggreko, we understand that providing optimal temperature control goes beyond delivering heating or cooling equipment. It’s about ensuring the environments where people work, and critical processes run are not only comfortable and efficient but also safe and healthy.
Our long-standing expertise positions us as a trusted partner, helping businesses navigate the complexities of environmental control, including air quality and microbial risk management.
We design our temperature control solutions with these critical considerations firmly in mind. While we provide robust and reliable cooling systems, our commitment extends to supporting practices that mitigate risks associated with bacteria in air conditioning units, including Legionella.
Our team works closely with our clients to understand their specific operational needs and environmental challenges, offering solutions that are powerful, efficient and adhere to the highest standards of safety and maintenance. Whether it’s through providing well-maintained, high-performance equipment or advising on best practices for system management, Aggreko helps you create environments that contribute positively to well-being.
Ultimately, investing in proper air conditioning and Legionella risk management is a strategic investment in the health, safety and operational continuity of your enterprise. A healthy environment reduces absenteeism, boosts productivity and protects your reputation. By partnering with Aggreko, you’re gaining a partner dedicated to supporting your commitment to a safe, productive and efficient future.
Contact Aggreko today to discuss your specific needs and discover how our safe, efficient and reliable solutions can support your business.