Legionnaires' Disease - Carrying out a written Risk Assessment

The level of risk assessment will depend upon the water system.  Simple systems of very low risk may only require a simple assessment whilst complex, high risk systems (eg. water systems incorporating cooling towers), will require a very detailed assessment. Ensure that the risk assessment is carried out by a competent person and that employees are consulted during the risk assessment process.  

When carrying out the assessment:

1. Identify potential sources of risk.

• Identify and assess sources of risk, for example, identify any systems which contain water likely to be >20°C and <55°C which may release a spray of water droplets.
• Identify the source and quality of the system supply water, for instance whether or not from mains water.
• Identify any possible sources of contamination of the supply water within the premises.
• Look at physical conditions, for example, the design and condition of the water system.
• Identify any infrequently used water outlets such as infrequently used showers and taps.

2. Decide who might be harmed and how.

• Identify any particularly susceptible or sensitive groups of employees.
• Take account of other people who may be affected by your operations, for example, members of the public.
• Consider the duration and frequency of personal exposure to the aerosol, for example how often a person may be exposed and for how long.
• Consider if there is potential for water droplets to be dispersed over a wide area.
• Take account of the normal operation of equipment and also reasonably foreseeable conditions, for instance, equipment breakdowns.

3. Evaluate the risks and decide on precautions.

If a risk is identified consider whether or not the risk can be avoided, for example can a wet cooling system be substituted with a dry air cooling system.

• Eliminate stagnation in the water system – for example, where possible remove dead legs (sections of pipe leading to a fitting through which water only passes when there is a draw off from the fitting) and blind ends (pipe work that has been altered or capped such that water cannot flow through it).
• Control the release of water spray / aerosols, for example, use drift eliminators on cooling towers in order to limit aerosol dispersal.

If the risks can be eliminated and the appropriate action is taken, then the assessment is complete but the assessment must still be regularly reviewed.

If the risk cannot be eliminated then adequate control measures must be put in place:

• Appoint someone to manage the control measures.  Ensure that roles and responsibilities are clearly defined, for instance for employees and contractors.  Ensure that any service providers working for you are competent.
• Inhibit growth physically, chemically or by other suitable methods. For example, insulate pipe work so that cold water is kept cold and hot water is kept hot; keep cold pipes well separated from hot pipes and other sources of heat, avoid temperatures that support growth of the bacteria.  Use biocides or other suitable treatment strategies if appropriate.
• Manage and monitor your control measures. Maintain equipment to ensure that it operates safely and correctly.  For example, keep equipment clean, control scale and corrosion and protect water storage vessels from contamination and thermal gain.
• Provide appropriate training and instructions to employees.

4. Record your findings and implement them.

• Record the results of the risk assessment. Cross reference any relevant health and safety documentation in the assessment.
• Document the written scheme for preventing or controlling the risk for example, what biocide concentration is being used, temperature measurements and the checks that are to be carried out. Document what remedial action is to be taken if controls fail.
• Describe the safe and correct operation of plant and equipment, prepare documented procedures.
• Keep an up to date schematic diagram of your systems.  The diagram should show any dead legs, all system control valves, standby valves, water treatment plant, dosing points, drain valves and make up water supply.
• Retain any documentation and records. Records of operation and maintenance of the system should include when the plant and equipment has been or not been in operation, when parts have been isolated, results of any inspection, tests or remedial action. All test and inspection records must be kept for 5 years from the date of the inspection and be available for inspection by an Inspector from the Authority.

5. Review your risk assessment and update if necessary.

• Review your risk assessment at regular intervals and especially if significant changes are made for example, changes to plant and equipment design or operation, changes to the building or water treatment, if personnel change or if lack of control is evident.

PRECAUTIONS CHECKLIST

Have you?

Carried out a Risk Assessment of all water systems in your premises?
Cleaned and disinfected all systems which produce aerosols?
Set up a system of flushing and temperature monitoring?
Put in place procedures to inspect tanks, clean showers, calorifiers and any other systems that may produce aerosols?
Engineered out deadlegs where possible?
Set up procedures for regular Legionella bacteria testing on site?
A chemical treatment programme or installed filters to eliminate the risk from the Legionella bacteria?