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Legionnaires’ disease is a potentially fatal form of pneumonia caused by the inhalation of small droplets of contaminated water containing Legionella bacteria

All hot and cold-water systems such as; Air conditioning systems, Spa pools and hot tubs and Showers, taps and toilets are likely, if not controlled appropriately, to provide an environment where Legionella can grow.

Where conditions are favourable i.e.

  • suitable growth temperature range
  • water droplets (aerosols) produced and dispersed
  • water stored and/or recirculated
  • some ‘food’ for the organism to grow such as rust, sludge, scale, biofilm etc.

then the bacteria may multiply, thus increasing the risk of exposure.

An employer, or a person in control of a work premises, is responsible for the health and safety of those using the premises and needs to take the right precautions to reduce the risks of exposure to legionella.

Therefore, they must understand how to:

  • identify and assess sources of risk
  • manage any risks
  • prevent or control any risks
  • keep and maintain the correct records
  • carry out any other duties you may have

The bacteria multiply where temperatures are between 20 – 45°C but are dormant below 20°C and do not survive above 60°C.

Therefore, the primary method used to control the risk from Legionella is water temperature control with systems operating at temperatures that prevent Legionella growth:

  • Hot water storage cylinders (calorifiers) should store water at 60°C or higher
  • Hot water should be distributed at 50°C or higher (thermostatic mixer valves need to be fitted as close as possible to outlets, where a scald risk is identified).
  • Cold water should be stored and distributed below 20°C.

A competent person should routinely check, inspect and clean the system, in accordance with the risk assessment.

‘Sentinel’ outlets (furthest and closest to each tank or cylinder) must be identified for monthly checking of the distribution temperatures, the hot water storage cylinder temperatures checked every month and cold-water tank temperatures at least every six months.

Stagnant water favours Legionella growth, to reduce the risk, dead legs / dead ends in pipe-work should be removed and infrequently used outlets (including shower heads and taps) flushed out at least weekly with cleaning and de-scaling of shower heads and hoses at least quarterly.

Cold-water storage tanks should be cleaned periodically and water should be drained from hot water cylinders to check for debris or signs of corrosion.

For further information on Legionella Assessment and Control contact Acorn Health & Safety or enrol on our E-Learning course ‘Basic Legionella Management’. The 75 minute course is interactive video based training aimed at all employers and staff to assist them in identifying the danger that legionella poses, as well as covering ways to identify and assess sources of risk from legionella in the premises also implement and manage a control programme.

Nigel Braybrooke, Grad. IOSH Health and Safety Consultant

Contact us now for further details