HSE'S L8 - "Legionnaires' disease:

The control of legionella bacteria in water systems"

Approved Code of Practice (ACoP) and Guidance - Part 3

Part 1: The Approved Code of Practice

Scope and application

ACOP

18 - This Approved Code of Practice applies to the control of legionella bacteria in any undertaking involving a work activity and to premises controlled in connection with a trade, business or other undertaking where water is used or stored and where there is a means of creating and transmitting water droplets which may be inhaled, thereby causing a reasonably foreseeable risk of exposure to legionella bacteria.

19 - A reasonably foreseeable risk of exposure to legionella bacteria exists in:

(a) - water systems incorporating a cooling tower;

(b) - water systems incorporating an evaporative condenser;

(c) -hot and cold water systems; and

other plant and systems containing water which is likely to exceed 20°C and which may release a spray or aerosol (ie a cloud of droplets and/or droplet nuclei) during operation or when being maintained. Guidance

20 - Experience has shown that cooling towers, evaporative condensers and hot and cold water systems in a wide variety of workplaces present a risk of exposure to legionella bacteria. Further guidance on systems that may present a risk can be found in Part 2. Not all of the systems listed in paragraph 19 will require elaborate assessment and control measures. A simple risk assessment may show that the risks are low and in such case no further action will be necessary. Examples include small, domestic-type water systems where temperatures and turnover are high, or where instantaneous water heaters are used.

21 - A water system includes all plant/equipment and components associated with that system, eg all associated pipe-work, pumps, feed tanks, valves, showers, heat exchangers, quench tanks, chillers etc. It is important that the system is considered as a whole and not, for example, the cooling tower in isolation. Deadlegs and parts of the system used intermittently, eg test loops in engineering factories and injection moulding machines, also need to be included as part of the system since they can create particular problems with microbial growth going unnoticed. Once brought back on-line they can cause heavy contamination, which could disrupt the efficacy of the water treatment regime.

22 - For other systems, such as humidifiers and air washers, spa baths and pools, car/bus washes, wet scrubbers, indoor fountains and water features, advice on control measures is given in the text and in Table 3 of Appendix 1.

Identification and Assessment of the Risk

Regulations

Control of Substances Hazardous to Health Regulations 1999, Regulation 6

Management of Health and Safety at Work Regulations 1999, Regulation 3

Health and Safety at Work etc. Act 1974, Sections 2, 3 and 4.

ACOP

23 - A suitable and sufficient assessment is required to identify and assess the risk of exposure to legionella bacteria from work activities and water systems on the premises and any necessary precautionary measures. The assessment is carried out by or on behalf of:

(a) - the employer, where the risk from their undertaking is to their employees or to others; or

(b) - a self-employed person, where there is a risk from their undertaking to themselves or to others; or

(c) - the person who is in control of premises or systems in connection with work where the risk is present from systems in the building (eg where a building is let to tenants but the landlord retains responsibility for its maintenance).

24 - In conducting the assessment, the person on whom the statutory duty falls is required to have access to competent help to assess the risks of exposure to legionella bacteria in the water systems present in the premises and the necessary control measures.

25 - The assessment should include identification and evaluation of potential sources of risk and:

(a) - the particular means by which exposure to legionella bacteria is to be prevented; or

(b) - if prevention is not reasonably practicable, the particular means by which the risk from exposure to legionella bacteria is to be controlled.

26 - Where the assessment demonstrates that there is no reasonably foreseeable risk or that risks are insignificant and unlikely to increase, no further assessment or measures are necessary. However, should the situation change, the assessment needs to be reviewed and any necessary changes implemented.

27 - The assessment needs to be reviewed regularly and, in any case, whenever there is reason to believe that the original assessment may no longer be valid.

Extracted from "Approved Code of Practice (ACoP) and Guidance "Legionnaires' disease: The control of legionella bacteria in water systems" (L8)" © Crown copyright

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