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Legionella Control

What is Legionnaires’ disease? 
Legionnaires’ disease is a potentially fatal pneumonia caused by legionella bacteria. It is the most well-known and serious form of a group of diseases known as legionellosis. Other similar (but usually less serious) conditions include Pontiac fever and Lochgoilhead fever. Infection is caused by breathing in small droplets of water contaminated by the bacteria. The disease cannot be passed from one person to another. Everyone is potentially susceptible to infection but some people are at higher risk, eg those over 45 years of age, smokers and heavy drinkers, those suffering from chronic respiratory or kidney disease, and people whose immune system is impaired.

Where are legionella bacteria found?
Legionella bacteria are common in natural water courses such as rivers and ponds. Since legionella are widespread in the environment, they may contaminate and grow in other water systems such as cooling towers and hot and cold water services. They survive low temperatures and thrive at temperatures between 20-45°C if the conditions are right, eg if a supply of nutrients is present such as rust, sludge, scale, algae and other bacteria. They are killed by high temperatures.

What are my duties under the law?
Under general health and safety law, you have to consider the risks from legionella that may affect your staff or members of the public and take suitable precautions. As an employer or a person in control of the premises (eg a landlord), you must:

  • Identify and assess sources of risk;
  • prepare a scheme (or course of action) for preventing or controlling the risk;
  • Implement and manage the scheme – appointing a person to be managerially responsible, sometimes referred to as the ‘responsible person’;
  • keep records and check that what has been done is effective; and
  • If appropriate, notify the local authority that you have a cooling tower(s) on site (see ‘Other duties’).

If a person working under your control and direction is treated as self-employed for tax and national insurance purposes, they may nevertheless be your employee for health and safety purposes. You may need therefore to take appropriate action to protect them.
If you do not wish to employ workers on this basis, you should seek legal advice. Ultimately each case can only be decided on its own merits by a court of law.

Assessing the risk
The risk assessment is your responsibility as the employer or person in control of the premises. You may be able to carry out the assessment yourself but, if not, you should call on help and advice from within your own organisation or, if this is not available, from outside sources, eg consultancies.

You need to find out if your water systems (including the equipment associated with the system such as pumps, heat exchangers, showers etc) are likely to create a risk.

Ask yourself the following:

  • Are conditions present which will encourage bacteria to multiply? For example, is the water temperature between 20-45°C?
  • Is it possible that water droplets will be produced and, if so, could they be dispersed over a wide area? For example, consider showers and aerosols from cooling towers.
  • Is it likely that anyone particularly susceptible will come into contact with the contaminated water droplets?


Managing the risk
You need to appoint someone to take responsibility for managing the control scheme that you have put in place. The ‘responsible person’ needs to be competent – that is, they need to have sufficient knowledge and experience of your system to enable them to manage and control the scheme effectively. If there are several people responsible for managing the system and/or control scheme, for example because of shift-work patterns, you need to make sure that everyone knows what they are responsible for and how they fit into the overall management of the system.

If you decide to employ contractors to carry out water treatment or other work, it is still the responsibility of the appointed person to ensure that the treatment is carried out to the required standards and remember, before you employ a contractor, you should be satisfied that they can do the work you want to the standard that you require. A Code of Conduct for service providers has been prepared to help you with this (see Further Information section for details).

What records do I need to keep?
If you employ five or more people you must record the significant findings of your risk assessment. This means writing down the significant findings of the assessment and details of any monitoring or checking carried out.

If you have fewer than five employees you do not need to write anything down, although it is useful to keep a written record of what you have done.

You also need to keep records of your written scheme and who is responsible for managing that scheme. You should also keep the results of your routine monitoring. You need to keep these records for a minimum of five years.

Does anybody else have to do anything about legionella?
Yes. Anyone who is involved in the supply of water systems and their components (eg designers, manufacturers, water treatment companies and suppliers) has to make sure that such equipment is designed and made in such a way that it is safe to use at work and that it can be easily cleaned and maintained.

They should tell you what risks might be present and how you can operate and maintain the system safely.

If you are using products or services, for example, for water treatment, the suppliers must make sure that these are effective at controlling legionella and that they can be used safely at work.

They should also tell you if, while they are treating your system, they find any problems which could pose a significant risk of legionella exposure.

Do I have any other duties?
Yes. If you have a cooling tower or evaporative condenser on site you must, under the Notification of Cooling Towers and Evaporative Condensers Regulations, notify the local authority in writing with details of where it is located. You must also tell them when/if such devices are no longer in use. Notification forms are available from your local environmental health department.

If you have a case of legionellosis in an employee who has worked on cooling towers or hot water systems that are likely to be contaminated with legionella, you have to report this under the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations.



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