Which standards apply to a Legionnaires’ disease risk assessment?
A Legionnaires’ disease risk assessment should follow the Health and Safety Executive’s ACOP L8 and HSG274 Part 2 guidance, with BS 8580-1 providing the standard for conducting risk assessments of water systems. Together, these establish expectations for identifying hazards, evaluating risks and documenting suitable control measures.
Legislation provides the legal foundation
The main legal duties in Great Britain arise from the Health and Safety at Work etc. Act 1974 and the Management of Health and Safety at Work Regulations 1999. These require employers and relevant dutyholders to assess health and safety risks, put suitable controls in place and appoint people with appropriate competence to manage them.
Legionella bacteria are also covered by the Control of Substances Hazardous to Health Regulations 2002 (COSHH), because exposure can result from inhaling contaminated water droplets or aerosols. COSHH requires the risks from hazardous substances to be assessed and controlled. A Legionnaires’ disease assessment should therefore sit within the organisation’s wider health and safety management system rather than being treated as an isolated inspection.
In Northern Ireland, equivalent duties are supported by the relevant health and safety legislation and guidance administered by HSENI. A risk assessment should reflect the jurisdiction in which the premises operates, particularly where legal terminology or regulatory guidance differs.
ACOP L8 and HSG274
The Health and Safety Executive’s Approved Code of Practice L8, Legionnaires’ disease: The control of legionella bacteria in water systems, sets out practical measures for dutyholders. It explains expectations around appointing responsibility, identifying and assessing sources of risk, implementing controls, maintaining records and reviewing arrangements.
HSG274 provides more detailed technical guidance. Part 2 addresses hot and cold water systems, including the conditions that can allow legionella to grow and spread. It is particularly relevant to assessments involving storage tanks, calorifiers, water heaters, distribution pipework, outlets, showers, thermostatic mixing valves and little-used sections of a system.
ACOP L8 is not an Act of Parliament, but failing to follow its advice may be difficult to justify if an incident occurs and an alternative approach has not provided an equivalent or higher level of protection. HSG274 is guidance rather than legislation, so it should be applied intelligently to the actual design, use and condition of the system.
BS 8580-1
BS 8580-1 is the principal British Standard for carrying out Legionella risk assessments in buildings other than residential accommodation. It gives a systematic approach to defining the assessment scope, gathering information, examining the water systems, identifying hazards and recording the findings.
A BS 8580-1-based assessment would normally consider:
- the building’s use, occupancy and operating arrangements;
- the people who may be exposed, including those who may be more vulnerable to serious illness;
- the incoming water supply, storage arrangements, distribution routes and outlets;
- temperatures, stagnation, low-use outlets, dead legs and areas of poor circulation;
- equipment that creates aerosols, such as showers, spray taps, spa pools or process equipment;
- the condition, accessibility, cleanliness and maintenance requirements of relevant assets;
- existing monitoring, inspection, cleaning, disinfection and treatment arrangements; and
- the control measures required, together with responsibilities, timescales and evidence of completion.
The standard helps produce a consistent and auditable assessment, but it does not replace professional judgement. An assessor must still account for unusual layouts, changes in occupancy, temporary systems, specialist equipment and defects that are not apparent from drawings or records alone.
BS 8680 and water safety planning
BS 8680:2020, Water quality. Water safety plans. Code of practice, may also be relevant. It provides a broader framework for managing water safety from source to point of use. It can help organisations connect the Legionella assessment with governance, responsibilities, operational controls, incident planning and verification across the whole water system.
BS 8680 is especially useful for organisations managing several buildings, complex estates or multiple water safety hazards. It does not make the Legionella assessment unnecessary; instead, it helps place the assessment within a coordinated water safety plan.
Sector-specific guidance
Additional technical guidance may apply to particular premises. Healthcare organisations should consider the relevant NHS technical memoranda, including HTM 04-01 in England and corresponding technical guidance in the devolved nations. These documents address healthcare water systems, higher-risk patient groups, monitoring and operational control in greater detail.
Residential accommodation, care settings, educational premises, leisure facilities, industrial sites and workplaces may each require different emphasis. For example, a care environment may need a more detailed assessment of vulnerable residents and bathing facilities, while an industrial site may require consideration of process systems, evaporative equipment or areas with limited access. The governing principles remain the same, but the scope and control measures must reflect the actual exposure risk.
What the completed assessment should demonstrate
Regardless of which supporting standard is used, the finished document should show how conclusions were reached. It should identify the responsible dutyholder and competent assessor, define the areas and systems assessed, record significant findings and state which controls are in place or required.
It should also link recommendations to practical actions. Vague findings such as “improve maintenance” are less useful than specifying the affected asset, the risk created, the required remedy, the person responsible and the method for verifying completion. Drawings, schematic diagrams, asset records, temperature information, photographs and maintenance documentation can provide important supporting evidence.
Are these standards legally mandatory?
Not every British Standard is compulsory. Legislation and the underlying duty to control exposure are mandatory, whereas a British Standard generally represents recognised good practice. A dutyholder may adopt another technically sound method, but should be able to explain why it is suitable and how it achieves effective control.
For that reason, a credible assessment should identify the legal duties and guidance used, state the standard or methodology followed and explain any justified departures. It should then be reviewed when systems, building use, occupancy, responsible personnel or control arrangements change, and whenever an incident, monitoring result or investigation indicates that the existing assessment may no longer be adequate.
Using the correct standard does not mean applying a fixed checklist to every building. A competent assessment should show how the chosen guidance was interpreted for the system actually present, including any areas that could not be inspected directly or fell outside the agreed scope.
- Check which legislation, HSE guidance and British Standard underpin the assessment.
- Confirm that the assessor’s conclusions relate to observed site conditions, not only existing drawings or maintenance records.
- Look for clear reasons where a standard clause or recommendation has not been followed.
- Ensure limitations, assumptions and required follow-up inspections are recorded.
This makes the document easier to review when water systems, building use or management arrangements change.
Get advice on Legionnaires’ disease risk assessment standards
If you need to establish which standards and guidance should underpin your Legionnaires’ disease risk assessment, speak to Blue Fish Water Management Ltd for practical advice tailored to your premises and water systems.