Risk Assessment

Legionnaire’s disease is most commonly caused by the inhalation of water droplets contaminated with the Legionella bacteria. It is therefore important that systems susceptible to colonisation by Legionella, and which incorporate a potential means for creating and disseminating water droplets, are identified and the risk they present be assessed.

Water droplets are created in various ways such as spraying, bubbling, and following impact onto hard surfaces. Large drops may be reduced to respirable-size by further impact or evaporation. The smaller particles can persist in the air for long periods and will be carried on air currents.

A water risk assessment (WRA) must be completed for routine system operation and use and also for circumstances such as breakdown, abnormal operation, commissioning, or other unusual circumstances. Once the assessment has been completed a prevention /control strategy can be prepared based on the level of risk.

The Council has appointed accredited Legionella consultants to provide professional services in relation to the identification and management of risks relating to water services (pipe work, taps, showers, mixers, cold-water tanks, hot water cylinders, air conditioning, fire hoses & sprinklers) and has made an assessment of the risks.

The risk assessment takes account of:

• The potential for formation of droplets.

• The condition of the water.

• Hot water temperature.

• Cold water temperature.

• The water turnover rate.

• The susceptibility of persons exposed to droplets.

• The population density exposed to droplets.

The report produced for each site includes the following:

• Survey of all relevant services.

• Plans and schematics of the services.

• Condition of the water services and equipment.

• Assessment of risks.

• Summary of remedial work recommendations.

• A list of routine actions to be taken by specific duty holders at specified intervals.