Legionnaires Disease

Recent outbreaks in the UK have once again brought to the public’s attention concerns relating to the role of air conditioning equipment in the spread of legionnaires disease. But what is Legionnaires disease and what steps can you take to prevent an outbreak in your building?

The Facts

Air Conditioning and Legionnaire’s Disease

Occasional outbreaks of Legionnaire’s Disease in the UK in recent years have created concerns surrounding the possible links between the disease and air conditioning systems back to the attention of the public. But what are the symptoms of Legionnaire’s Disease and how can businesses help to prevent its spread?

What is Legionnaire’s Disease?

Legionnaire’s (Legionellosis) is caused by Legionella Pneumophila, a bacterium usually found in streams, rivers and lakes. There are two basic forms of the infection:

  • Legionnaire’s Disease is a serious form of the Legionellosis infection. Symptoms include chills, fever, a cough, tiredness and fatigue, headache and muscle ache and decreased appetite. Distinguishing Legionnaire’s Disease can be difficult, as chest scans and X-rays taken from patients can often present as pneumonia. Additional tests will be required for a patient to be firmly diagnosed with Legionnaire’s Disease.
  • Pontiac Fever, which is a milder form of Legionellosis does not include pneumonia-loke symptoms. Symptoms include muscle ache and fever. Patients suffering from Pontiac Fever typically recover within 2-5 days with no need for medical treatment. The onset of Pontiac fever typically occurs within 2 hours and up to 2 days following exposure and Legionnaire’s Disease within 2-10 days of exposure.

Who can contract Legionellosis?

Anyone can contract Legionnaire’s Disease. However, the illness typically affects individuals with a compromised immune system, chronic diseases that affect the lungs, smokers or those who are middle aged or older.

How is Legionellosis contracted?

Legionnaire’s Disease is most commonly contracted when an individual inhales fine mist from a source of water that has been contaminated with the Legionella Pneumophila bacterium.

  • For Legionella Pneumophila to multiply, organic matter such as algae, rust, scale or sludge should be present to provide the bacteria with nutrients to feed on. Water temperature should be between 20C-45C.
  • Legionnaire’s Disease is not contagious in that it cannot pass from patient to patient. For illness to occur, a susceptible or vulnerable person needs to come into contact with breathable droplets of contaminated water.

Where can Legionellosis be contracted?

Legionella Pneumophila bacteria can be found within:

  • Whirlpool spas
  • Cooling towers
  • Humidifiers
  • Hot water tank-supplied showers
  • Some types of water-cooled air conditioning systems

Can Legionella contamination be prevented?

The primary cause of air conditioning and Legionnaire’s Disease contamination is poor maintenance and design. One of the most effective means of protecting the system from contamination, and therefore protecting you and the occupants of the building from Legionnaire’s Disease is by installing a system that uses air-cooled refrigerant. This avoids water mist or aerosols associated with water-based systems which means that the system carries absolutely zero risk of Legionella contamination. When a water-based system is used, the system should undergo regular maintenance checks and should be cleaned regularly in order to prevent the build-up of the algae, rust, sludge and scale that can provide the perfect environment for the Legionella bacteria to flourish.

What should I do if I think my air conditioning system is at risk?

If you suspect that your air conditioning system is at risk of contamination, we recommend seeking urgent advice from a trained professional. Should a Legionella outbreak occur, the relevant authorities will likely investigate whether you could have done more to prevent the outbreak and to safeguard the occupants or those in and around the building.

To learn more about the responsibilities of employers, visit: http://www.hse.gov.uk/pubns/iacl27.pdf, and to learn more about the responsibilities of those who provide residential accommodation, visit: http://www.hse.gov.uk/pubns/indg376.pdf

What can I do if my system is already contaminated?

Options are available for systems that may already be contaminated, including ionisation, chlorination and heat treatments. You should contact a trained expert should an outbreak occur for expert advice on preventing contamination outbreaks in the future and on decontaminating existing equipment.


Any air conditioning system installed and/or maintained by the team at Andrews Air Conditioning is not at risk of Legionella contamination. We specialise in systems that use an air-cooled refrigerant, which means that the requisite environment for the spread of bacteria is not present.

Please note that the information provided here should be used as a guide only and should not replace information from a medical practitioner or from your Local Authority. For further information on air conditioning and Legionnaire’s Disease please contact Andrews Air Conditioning, or if you have any concerns, your Local Authority or medical practitioner.

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