Legionella Control Scheme and Management
On completion of the risk assessment, if the dutyholder assesses that the risks associated with legionella are controlled or mitigated by the existing control measures within the practice then these should be documented as part of the written control scheme . To minimise the risk of legionella infection additions or amendments would need to be made to this when the current control measures are assessed to be insufficient, when there are changes to the water system or a significant legionella breach arises . This might also be necessary if, when carrying out the risk assessment, it is not possible to access all parts of the water system (e.g. due to the fabric of the building).
The risk assessment and control measures must be reviewed regularly and specifically when there is any reason to believe that the previous risk assessment may no longer be valid (e.g. a change to the water system, checks indicate control measures are no longer effective or a significant legionella breach arises).
The dutyholder should appoint a competent person or persons, known as the ‘responsible person’, to take day-to-day responsibility for controlling any identified risk from legionella bacteria. The responsible person can be the employer one or more employees or someone contracted for this purpose. It is important that the appointed responsible person has sufficient authority, competence and knowledge of the practice’s water systems to ensure that all operational procedures are carried out effectively and in a timely way .
Minimising the release of droplets and ensuring that water conditions prevent the proliferation of legionella bacteria are key factors in controlling the risks associated with legionella. Measures may include:
- Minimising spray and aerosols (e.g. high-power aspiration at the dental chair, lower speed handpieces)
- Ensuring that water is at a temperature that does not favour bacterial growth (i.e. <20°C and >45°C)
- Ensuring that water cannot stagnate (e.g. running hot and cold water outlets each day; following the DUWL flushing and draining regime; having redundant pipework removed)
- Avoiding materials that encourage bacterial growth (e.g. using fittings, materials, and appliances approved for use in the UK )
- Keeping the systems and water clean (e.g. using anti-retraction devices with dental instruments attached to DUWL or the dental chair unit (DCU); inspecting DUWL bottles each day when filling or decontaminating; use of filters)
- Treating the water to kill legionella or limit its growth (e.g. use of a biocide in DUWLs and DCUs as recommended by the manufacturer)
This is documented in the written control scheme. A written control scheme should include [1,4,5]:
- A description of the water system (including pipework, pumps, valves, cold water supply/storage tanks, hot water generation/storage tanks, sinks, toilets, showers, air-conditioning units, dental unit water lines)
- The person responsible for carrying out the risk assessment and managing the implementation of the written scheme
- Any significant findings of the risk assessment and modifications to eliminate the risks
- The safe and correct operation of the water system
- Details of the control measures used to minimise the risk of legionella exposure (e.g. how to monitor water temperature using a calibrated thermometer, including the frequency of monitoring)
- The checks carried out to ensure the risks are being managed, including their frequency.
- An action plan to be followed if the written scheme is shown to be ineffective thereby increasing the risk of colonisation, or there is a significant legionella breach. The plan will include who should be notified (e.g. Health Board contact).
Regular monitoring is necessary to ensure that precautions remain effective. This should be overseen by the responsible person and involves competent member(s) of staff checking the condition and performance of the water system, checking for signs of contamination, ensuring that control measures specified in the written control scheme are being carried out effectively and initiating remedial action, if required. The responsibilities within the practice for legionella risk assessment and control should be documented, for example within a policy on legionella control (see Legionella Policy and Procedures template).
The written control scheme should be retained while the water system is current and for a further two years. The results of any monitoring inspection, test or checks carried out, with dates, should be retained for at least five years .
The HSE provides a summary of the regulatory requirements in Legionnaires’ disease, a brief guide for dutyholders  and further details provided in Legionnaires’ disease: the control of legionella bacteria and water systems. (Approved Code of Practice L8, Fourth edition)  and HSG 274 Legionnaires’ disease Part 2: The control of legionella bacteria in hot and cold water systems . Specific DUWL guidance is provided by Health Protection Scotland in Literature and Recommendations: Management of Dental Unit Waterlines .
Sources of Information
- Legionnaires’ disease: the control of legionella bacteria and water systems. (Approved Code of Practice L8, Fourth edition, 2013). Health and Safety Executive
- Literature and Recommendations: Management of Dental Unit Waterlines (version 2.0, 2019). Health Protection Scotland
- Water Regulations Advisory Scheme
- Legionnaires’ disease, a brief guide for dutyholders (2012). Health and Safety Executive
- HSG 274 Legionnaires’ disease Part 2: The control of legionella bacteria in hot and cold water systems (2014) Health and Safety Executive