By Andrew Arnold
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A Legionella risk assessment is not just a tick-box exercise; it is the foundation of a legally compliant water safety management system. Its quality directly dictates the effectiveness of all subsequent control measures and, ultimately, the safety of the building's occupants. In the UK, the benchmark for a robust and accurate assessment is the British Standard BS 8580-1:2019, which outlines the requirements for legionella risk assessment. A "good quality" assessment means one that is detailed, accurate, and reflects the true risk profile of the system. For the dutyholder, understanding the importance of this standard is key to fulfilling their legal obligations under the Health and Safety at Work etc Act.
The Importance of Assessor Qualifications and Experience
The cornerstone of a compliant and useful risk assessment is the competence of the individual carrying it out. BS 8580 places strong emphasis on the qualifications and experience of the assessor, because a person lacking the necessary skills may miss critical hazards or misinterpret system design.
- Training and Certification: The assessor must possess verifiable training in water hygiene, Legionella control, and a deep understanding of relevant guidance, particularly HSG274 (Parts 1, 2, and 3).
- System Knowledge: Experience across various water system types (e.g., cold water storage, hot water recirculating systems, cooling towers) is crucial. A competent assessor understands how thermal dynamics, water stagnation, and material choices contribute to microbial risk.
- Benefits of Quality: A qualified assessor goes beyond listing assets; they provide a suitable and sufficient assessment that identifies foreseeable risks and proposes proportionate control measures, saving the dutyholder time and unnecessary expense later on.
Site Knowledge, Records, and Accurate System Schematics
A risk assessment cannot be accurate if it is performed in isolation. BS 8580 stresses the need for the assessor to collaborate with the Responsible Person and leverage site assistance and knowledge.
- System Traceability: The assessment must be supported by an accurate schematic drawing of the water system. Without it, areas of stagnation or contamination (such as "dead legs" or unused pipework) are impossible to identify and control.
- Availability of records: The dutyholder must make all relevant records available, including previous risk assessments, monitoring logs (temperature, biocide levels), maintenance reports, and cleaning/disinfection certificates. These records provide a history of control effectiveness and highlight any recurring failures or trends that must be addressed.
- Active Consultation: The assessor should actively consult with site staff to understand daily use patterns, system function during periods of low occupancy (which causes stagnation), and any known issues or maintenance backlogs.
Review Frequency: When to Update the Assessment
The risk assessment is a living document, not a static report. Conditions within a water system can change rapidly, and the assessment must be reviewed regularly to remain valid. HSG274 specifies the key times when the Legionella risk assessment should be reviewed and updated:
- Routine Review: It must be reviewed regularly and specifically whenever there is reason to suspect it is no longer valid. A risk assessment report should provide a recommended review date by which it must be reviewed. Review should be considered sooner in the following scenarios as advised in the ACoP L8 and HSG274:
- A change to the water system or its use
- A change to the use of the building where the system is installed
- New information available about risks or control measures
- Results of checks that indicate control measures are no longer effective
- Changes to key personnel
- A case of Legionnaires' disease/Legionellosis associated with the system
Failing to review the assessment when changes occur means the control measures may no longer cover the actual risk, potentially leading to a compliance failure.
An investment in a high-quality, BS 8580 compliant Legionella risk assessment is an investment in safety and legal compliance. By prioritising the competence of the assessor, ensuring the document is supported by detailed site knowledge and records, and maintaining a strict review schedule, dutyholders can ensure their control scheme is robust, defensible, and effective in mitigating the risk of Legionnaires' disease.