What Is a Legionella Risk Assessment?

The resulting assessment should identify:

1. The systems examined, their use and the limits of the inspection.
2. Potential sources of exposure and people who could be affected.
3. Existing controls and evidence of how they perform.
4. The people responsible for managing the system and carrying out checks.
5. Gaps, recommended actions and arrangements for reviewing the assessment.

HSE explains these requirements in its guidance on identifying and assessing sources of risk. Choose an assessor whose competence matches the installation's complexity, rather than assuming experience with one type of system covers every building.

The scope must expressly identify the water systems being assessed. Hot and cold water services, evaporative cooling towers and other systems present different operating conditions and need appropriate technical knowledge.

For a cooling tower, the assessment needs to consider the wider evaporative cooling system, including associated equipment and water management. A mechanical service report about fans, pumps or drive components does not replace this assessment. Equally, the presence of a chiller does not automatically mean a building has an evaporative cooling tower. Confirm the installation and its heat-rejection arrangement.

HSE's cooling tower guidance explains the system-specific control considerations.

Provide current system drawings, previous assessments, operating information, maintenance and monitoring records, details of alterations and access to relevant areas. Identify who controls each system, especially where landlords and occupiers share responsibilities.

Afterwards, turn the findings into assigned actions with priorities and completion evidence. Where a control scheme is required, connect it to the assessment and the people implementing it. Retain records together so a change of contractor or building manager does not lose the reasons behind the controls.

Review the assessment regularly and when changes or evidence suggest it is no longer valid. Examples include altered pipework, different occupancy, prolonged disuse or concerns about control effectiveness. HSE's review guidance supports checking the system description, responsibilities and monitoring arrangements together.

No. Sampling provides information about the water sampled at that time and location. The assessment considers the whole risk-management arrangement. Sampling requirements and the response to results belong within the system's control arrangements; see HSE's testing and monitoring guidance.

There is no single annual replacement rule for every installation. Set review arrangements suited to the system and its risks, and act sooner when relevant circumstances change. A review determines whether the existing assessment remains suitable and what needs updating.

Appointing assistance does not remove the dutyholder's responsibility. Agree the contractor's scope, access, reporting and escalation arrangements, and identify who authorises and closes recommended actions.

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