Legionella Risk Assessment in Dental Practices


The recent publication of Health Technical Memorandum 01-05: Decontamination in primary care dental practices (HTM 01-05) re-emphasises the requirement for risk assessments to be undertaken for the control of legionella bacteria in water systems.  Paragraph 19.2 states ‘All premises are required to have a written scheme and a legionella risk assessment for controlling any identified risk in accordance with with the Health and Safety Executive’s Approved Code of Practice L8’ (2).

This requirement is not new (L8 was first published in 1992) but is restated in the context of how it applies for dental practices. In particular it places the onus on the Registered Manager to ensure that there is a risk assessment, an operational plan and a programme of staff training.

The risk assessment will need to identify what water systems are present and where these may pose a risk. On one level this may appear simple but the assessor is required to consider factors such as the management controls, operating procedures, normal and abnormal operating criteria, persons with the potential to be exposed and identify potential problems with the systems.  HTM 01 – 05 states that the risk assessment should be carried out by a Competent Person.


Legionella bacteria are ubiquitous in nature and commonly colonise air conditioning plant, water storage tanks, hot and cold water distribution systems and spa baths. Where conditions are right the bacteria can multiply to significant numbers and present a risk.  Infection is caused by the inhalation of Legionella bacteria in the form of an aerosol.  To cause infection the bacteria therefore needs to become airborne for example from a shower or spray tap.  Though few in number infections have been linked to infection from water to equipment served from dental unit water lines.

Legionellosis is a generic term given to respiratory infections, such as Legionnaire’s disease, caused by Legionella bacteria. Over fifty different species of Legionella have been identified.  Only a few species have been directly associated with outbreaks of infection. Legionella pneumophila Serogroup 1 is the most commonly identified form of the bacteria and is responsible for over 80% of the fatalities arising from Legionnaire’s disease.  On average there are around 300 – 350 reported cases of Legionnaires’ disease in the United Kingdom per annum though few have actually been positively linked to dental equipment.

The potential for legionella bacteria to present a risk in dental practices has long been recognised.  A report by B A Oppenheim and Others (1) in 1987 recognised the widespread colonisation of dental stations by legionella pneumophila but also noted that this did not correlate to high numbers of infections.  Design of equipment, material composition and operating procedures have all progressed since in the light of knowledge of the implication of colonisation by pathogens but further controls are still necessary.

Legislation and Guidance

The Approved Code of Practice, L8, the control of legionella bacteria in water systems is the principle document defining the controls required in respect to the risks from legionella bacteria.  Approved Codes of Practice give practical guidance on compliance.  Failure to comply with an Approved Code of Practice is not an offence in itself, however, these codes have special legal status.  If an employer/individual faces criminal prosecution under health and safety law, and it is proved that the advice of the Approved Code of Practice has not been followed, a court can regard it as evidence of guilt unless it is satisfied that the employer/individual has complied with the law in some other way.  Following Approved Codes of Practice is therefore regarded as best practice.

The regulatory framework extends to include consideration of legionella bacteria under COSHH (7), publications and regulations covering the design of water systems, such as British Standard 8558(8) and the Water Fittings Regulations (9). The principles of which are drawn on and extended into the healthcare environment through the NHS Estates Health and Technical Memorandum series principally HTM 04-01 – Safe water in healthcare premises.

HTM 04-01 focuses on: a) legal and mandatory requirements, b) design of systems, c) maintenance of systems and d) operation of systems It sets out items calling for action and cross references to the Code of Practice.

Where enforcement action has been brought by authorities through the criminal courts against premises owner and system operators this has often been seen to be ultimately under the Health and Safety at Work Act but to refer to the other Regulations and guidance notes. Civil actions have also been brought where there has been death or injury and have been seen to widely reference the full range of guidance notes and best practice documents.

Requirements for Control

HTM 01-05 Paragraphs 19.2 and 19.3 requires the Registered Manager to implement an operational plan for each site under their control and to implement a programme of staff training. The plan typically will include elements such as the physical drain down of all equipment daily, routine flushing of water lines, disinfection of equipment in line with equipment manufacturers’ recommendations, monitoring of water temperatures and similar.  The operational plan needs to be written down, to include schematic drawings and to have detailed operational instructions to attend to normal and out-of-line conditions.  The risk assessment and written scheme of control require review routinely, in the event of change, where controls are seen to have failed, in the event of infection or similar.


Publication of Health Technical Memorandum 01-05 emphasises the requirement for legionella risk assessment in dental practices. The requirement falls to the Registered Manager of the practice but requires that the assessment be undertaken by a Competent Person.

The risks identified are likely to be minimal but are foreseeable and invariably there will be a number of improvement actions and on-going control actions that are required to be implemented. Actions should be documented and finally processes put in place to ensure that the assessment, control scheme and staff training requirements are regularly reviewed so that they remain valid.



1 – OPPENHEIM BA, SEFTON AM, GILL ON, ET AL. Widespread Legionella pneumophila contamination of dental stations in a dental school without apparent human infection. Epidemiol Infect 1987; 99(1): 159-166.

2 – The Health and Safety Executive’s Approved Code of Practice, L8, the control of legionella bacteria in water systems

3 – NHS Estates HTM 01-05 2013: Decontamination in primary care dental practices (HTM 01-05)

4 – Health Technical Memorandum 04-01: Safe water in healthcare premises. Part A: Design, installation and commissioning

5 – Health Technical Memorandum 04-01: Safe water in healthcare premises. Part B: Operational management

6 – Health and Safety at Work etc. Act 1974, Sections 2, 3 and 4

7 – Control of Substances Hazardous to Health Regulations 2002

8 – BS8558:2015 Guide to the design, installation, testing and maintenance of services supplying water for domestic use within buildings and their curtilages. Complementary guidance to BS EN 806

9 – The Water Supply (Water Fittings) Regulations 1999


Related Case Study


If you'd like more information, please fill out the form below and we'll be in touch.

    © 2024 First Environment Ltd. Company registration no: 3224550

    Registered address: Cannock Chase Enterprise Centre, Walkers Rise, Hednesford, Staffs, WS12 0QU.