As a building manager or a person who is tasked with the maintenance of a building, it is your responsibility to ensure that appropriate building safety measures and precautions are in place to prevent and limit the risks of outbreaks such as legionnaires disease.

What is Legionnaires Disease?

Legionnaires disease is a form of bacterial pneumonia first discovered after an outbreak at an American Legion meeting in 1976. Legionnaires disease is transmitted through inhaling water droplets or soil contaminated with the legionella bacteria.

Legionella bacteria grows in conditions that allow the bacteria time to sit at temperatures between 20 to 45 degrees Celsius, legionella thrives in hot water tanks, air conditioning systems, evaporative condensers and cooling towers.

Cases of Legionnaires Disease

There have been reported outbreaks of legionnaires disease all over the world, one of the most recent cases in the UK is the charge against Brighton and Sussex University Hospitals NHS Trust, following the death of cancer patient Joan Rayment who contracted the disease before passing away in November 2011.

The Health and Safety Executive is prosecuting the trust under the Health and Safety at Work Act 1974 for failing to ensure its patients and visitors were protected from the risk of legionella bacteria.

Protect Your Building Against Legionella

There are a number of measures building managers can implement to prevent the growth of legionella and therefore an outbreak of legionnaires disease. As the bacteria are commonly found in hot water tanks, air conditioning systems, evaporative condensers and cooling towers, let’s take a look at the precautionary measures that should be taken for each.

Hot Water Tanks

The primary precaution to implement with hot water tanks to control the risk of legionella is temperature control. Water temperatures should be set at temperatures to prevent the growth of legionella:

  • Hot water should be stored at 60 degrees Celsius or higher
  • Hot water should be distributed at 50 degrees Celsius or higher (thermostatic mixer valves should be fitted as possible to outlets, where a scald risk is identified)
  • Cold water should be stored and distributed at 20 degrees Celsius or lower

Building managers should regularly inspect and clean the system and regularly flush out infrequently used outlets such as shower head and taps to avoid a stagnant water supply. Water samples should be analysed and tested for legionella periodically and in accordance with the risk assessment.

Air Conditioning Systems, Evaporative Condensers & Cooling Towers

Cooling towers and evaporative condensers are part of large modern air-conditioning systems. They are used to cool water and dissipate unwanted heat to the atmosphere through water evaporation.

Warm water flows into the top of the cooling tower through spray nozzles. While the water passes through the nozzles, tiny airborne droplets are formed, providing maximum contact between the water and the air moved through the tower by fans.

The following measures should be taken to prevent legionella growing in your air conditioning system:

  • Regularly check and clean your system
  • Ensure stagnant water doesn’t build-up, especially in periods of infrequent use i.e. Winter.