Legionnaire's Disease And Air Conditioning Systems: Vital Information For Building Facilities Managers

Legionnaire's disease is a severe form of pneumonia that experts believe infects up to 15,000 people in the United States every year. One of the reasons that people believe the disease is rare is that 65 to 80 percent of cases affect only one or two people, and it's only the larger outbreaks that gain attention. That aside, the Centers for Disease Control and Prevention (CDC) estimates that Legionnaire's disease kills nearly forty people each week. As such, it's extremely important that businesses take the necessary steps to prevent an outbreak. If you're a building facilities manager, learn more about how Legionnaire's disease can spread through air conditioning systems, and what you need to do to manage the risk of infection.

Causes of Legionnaire's disease

Legionnaire's disease is a bacterial infection that leads to a potentially fatal type of pneumonia. The bacteria that cause the disease belong to the Legionella genus, which includes 35 species that can cause the infection. These bacteria thrive in damp, water-logged environments, and can survive for several months in wet conditions. Legionella bacteria thrive where there are algae and organic matter in the water.

How Legionnaire's disease spreads through air conditioning systems

Scientists believe that Legionnaire's disease only occurs if Legionella microbes get into your lungs. As such, the most likely way to transmit the disease is where tiny particles of water get into the air supply, but the infection can also occur if you aspirate when drinking, allowing fluids and particles to get into the lungs by mistake. Air circulated in ventilation and air conditioning systems can transmit the bacteria that cause Legionnaire's disease.

Cooling towers cool water using a process of evaporation. As part of this process, cooled water collects at the bottom of the tower, and the system then reuses and recirculates this cooled water. Legionella bacteria can easily multiply in this cooled water, particularly if algae and scale build up in the tank. The microbes can then easily enter the air conditioning system, especially if parts are corroded or faulty.

Legionnaire's disease regulations

In the United States, there are no regulations that force businesses to test or maintain cooling towers to prevent Legionnaire's disease. That aside, Occupational Safety and Health Administration (OSHA) laws mean that employers have to provide their employees with safe working conditions. As such, if you don't take reasonable precautions to prevent Legionnaire's disease, you could breach these laws.

The OSHA recommends that high-risk businesses set up a risk management program to lower the risk of Legionella transmission. Certain facilities should carry out regular risk assessments to prevent any disease outbreak. For example, healthcare facilities should set up particularly rigorous controls.

Dealing with an outbreak

An outbreak of Legionnaire's disease officially occurs when two or more cases of infection are attributable to a building in a six-week period. According to the CDC, legionellosis is a notifiable disease, which means you must report any outbreak to the authorities. Other steps to take include:

  • Evacuation and isolation of high-risk people (most relevant in hospitals or healthcare facilities)
  • Carry out a building inspection to find all bacteria sources
  • Water sampling to assess bacteria levels
  • Shut down and treatment of affected systems and facilities

Building facilities managers should note that any source of water at more than 68 degrees Fahrenheit is a potential source of the outbreak. As such, you may need to treat multiple systems.

Prevention advice

Building facilities managers should set up robust controls and maintenance schedules to cut the risk of a Legionella outbreak. Actions to consider include:

  • Inspect and clean cooling towers and evaporative condensers at least once a year
  • Replace corroded parts immediately
  • Remove algae and scale as part of an ongoing cleaning and maintenance schedule
  • Install an automatic water treatment system to continuously manage circulating water quality
  • Use disinfectants that are compatible with the cooling tower construction materials
  • Routinely clean and replace air filters

The design of your air conditioning system is also vital. For example, you should not place fresh air intakes close to cooling towers, as this can help contaminated water particles get into the ventilation system.

Legionnaire's disease is a life-threatening form of pneumonia that can spread through air conditioning systems. Building facilities managers must make sure that the right controls are in place to stop bacteria building up and getting into the building air supply. Click here for more information.

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