Skip to content

Controlling Legionella in workplaces

If you are an employer, or someone in control of premises (including landlords), you must understand the health risks associated with legionella. This page contains information that can help you to control any risks.

What is Legionnaires' disease

Legionnaires' disease is a potentially fatal type of pneumonia, contracted by inhaling aerosols (airborne water droplets) containing legionella bacteria. Such aerosols can be created, by hot and cold water outlets; atomisers; wet air conditioning plant; and whirlpool or hydrotherapy baths. In a hot and cold water system outlets such as showers and spray taps are more likely to produce aerosols that can be inhaled by users. Anyone can develop Legionnaires' disease, but those at greatest risk include people whose immune systems are suppressed, elderly people, and those who have long-term illnesses, particularly of the respiratory system.

Could legionella be a risk in my premises?

Legionella bacteria are widely found in natural water sources but can also enter purpose-built water systems, cooling towers, evaporative condensers, hot and cold water systems, spa pools, etc. Any system that has the right environmental conditions could allow legionella to grow. There is a risk if:-

  • water is stored or re-circulated as part of your system;
  • the system has not been used for some time and had not been regularly maintained and flushed through;
  • the water temperature in all or some part of the system is between 20–45 °C;
  • there are sources of nutrients such as rust, sludge, scale and organic matters;
  • the conditions are likely to encourage bacteria to multiply;
  • it is possible for water droplets to be produced and, if so, if they can be dispersed over a wide area, eg showers and aerosols from cooling towers; and

If any users of the building are more susceptible to infection due to age, illness, a weakened immune system etc and could be exposed to any contaminated water droplets then the risk is increased.

What must I do?

Building managers need to carryout a risk assessment to identify any potential sources of legionella contaminated water which could produce aerosols. You must have regard to the Health and Safety Executive's Approved Code of Practice L8 and relevant technical guidance documents. If you are not competent to carryout this assessment yourself you may need to engage a specialist to do it for you. You should be satisfied that they can do the work you want to the standard that you require. Organisations such as the Legionella Control Association may be able to assist in identifying suitable service providers.

If you identify a risk you should implement steps that will help you to control legionella by describing

  • your system, eg draw a schematic diagram of the water system;
  • who is responsible for carrying out the assessment and managing its implementation;
  • the safe and correct operation of your system;
  • what control methods and other precautions you will be using;
  • what checks will be carried out to ensure risks are being managed and how often.
  • ensure that employees with responsibility for managing these controls are suitably trained. 

Keep adequate records of the results of any inspection, test or check carried out, and the dates

How can legionella be controlled?

It is important to design, maintain and operate your water systems under conditions that prevent or adequately control the growth of legionella bacteria. Where appropriate you should:-

  • 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 by removing redundant pipework;
  • avoid materials that encourage the growth of legionella. (The Approvals Directory references fittings, materials, and appliances approved for use on the UK Water Supply System by the Water Regulations Approvals Scheme);
  • keep the system and the water in it clean; and
  • treat water to either kill legionella (and other microorganisms) or limit their ability to grow.

If you employ more than 5 people your scheme for controlling legionella should be written down.

For further guidance read: