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, 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;

- 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.

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, e.g. 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.

The risk assessment is your legal 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, e.g. 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?

- Is it possible that water droplets will be produced and, if so, could they be dispersed over a wide area?

- Is it likely that anyone particularly susceptible will come into contact with the contaminated water droplets?

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).

If a risk is identified which cannot be prevented, you must introduce proper controls. Risks from legionella in water systems can be controlled but careful planning, a successful management policy, competent staff and attention to proper control strategies are all essential.

You should consider whether you can prevent the risk of legionella in the first place by looking at the type of water system you need. For example, is it possible to replace a wet cooling tower with a dry air cooled system?

You will need to prepare a written scheme which sets out how you intend to control the risk from legionella. The HSE provide full details about what should be included in the Scheme, but we recommend that you outsource this to a professional company who are experienced in this type of work. This is not something that you want to get wrong, the implications are severe.