Legionnaire's disease is a potentially fatal form of pneumonia that anyone can suffer from.

However, you are at a higher risk if you:

  • Are over 45
  • Smoke or drink heavily
  • Suffer from chronic respiratory or kidney disease
  • Have diabetes, lung or heart disease
  • Have an impaired immune system

The bacteria that cause the disease are common in natural water sources such as rivers, lakes and reservoirs, but usually in low numbers. They may also be found in purpose-built water systems such as cooling towers, evaporative condensers, hot and cold water systems and spa pools.

Legionnaire's Disease is contracted by breathing in small water droplets that contain the bacteria. The risk increases if:

  • The water temperature is between 20-45 °C, allowing the bacteria to multiply
  • Deposits such as rust, sludge, and organic matter provide a base and nutrients for bacteria
  • Aerosol water droplets can be produced and dispersed, such as cooling towers, shower heads, spa pools, ornamental fountains
  • Water is stored or recirculated as in many commercial buildings, including care homes and hospitals

If you have any of these factors then you need to carry out a risk assessment to identify any measures needed to eliminate or control the risk. For example, a cooling tower could be replaced with a dry system.

In most cases it is not possible to eliminate the risk, so you need to design, maintain and operate water services under conditions that prevent or adequately control the growth and multiplication of legionella.

You need to:

  • Ensure that the release of water spray is properly controlled
  • Avoid water temperatures and conditions that favour the growth of legionella and other micro-organisms
  • Ensure water cannot stagnate anywhere in the system by keeping pipe lengths as short as possible or removing redundant pipework
  • Avoid materials that encourage the growth of legionella. The Water Fittings and Materials Directory references fittings, materials, and appliances approved for use on the UK Water Supply System by the Water Regulations Advisory Scheme)
  • Keep the system and the water in it clean
  • Treat water to either control the growth of legionella or limit their ability to grow
  • Monitor any control measures applied
  • Keep records of these and other actions taken, such as maintenance or repair work

The approved Code of Practice for The Control of Legionella Bacteria in Water Systems is available from the HSE.

The HSE have also produced A Brief Guide for Duty Holders

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