Legionella

Risk Assessment

Health and safety regulations require employers to carry out an assessment of the risks to the health from hazardous substances present in the workplace. A suitable and sufficient risk assessment is required wherever exposure to legionella bacteria is likely to occur.

Where there are five or more employees a written copy of the risk assessment should be provided and employees should always be informed of any significant findings from the assessment process.

Understanding when employees and others may be exposed to legionella is important when conducting a risk assessment. All potential sources of exposure should be identified as well as who is likely to be exposed.

In general terms the employer, or the person in control of premises (e.g. a landlord), has a duty to manage risk.  Although all systems require a risk assessment, not all systems will require elaborate control measures. A simple risk assessment may show that the risks are low and being properly managed, meaning no further action may be required.

The control and management of legionella is considered specifically within an Approved Code of Practice & Guidance (ACOP) entitled Legionnaires’ disease, The control of legionella bacteria in water systems, L8

The ACOP states “A suitable and sufficient assessment must be carried out to identify and assess the risk of exposure to legionella bacteria from work activities and water systems on the premises and any precautionary measures needed.”

Further guidance for dutyholders, which includes employers and those in control of premises is contained within Legionnaires’ disease: Technical Guidance. The technical guidance, also referred to as HSG274, is in three parts, detailing control measures in various types of water systems (evaporative cooling systems, hot and cold water systems and other risk systems).

An effective risk assessment will consider the following:

• If the water temperature in all or some parts of the system is between 20–45°C (legionella will grow and multiply between these temperatures).
• Whether water is stored or re-circulated as part of the water system.
• The presence of nutrients such as rust, sludge, scale, organic matter and biofilms that can encourage growth of bacteria.
• The conditions likely to encourage bacteria to multiply.
• If it is possible for water droplets to be produced and, if so, whether they can be dispersed over a wide area, e.g. showers and aerosols from cooling towers.
• If it is likely that any employees, residents, visitors, etc are more susceptible to infection and whether they could be exposed to any contaminated water droplets.

It’s important to remember that the person who carries out the risk assessment and provides advice on prevention and control of exposure must be competent to do so.

Help and advice may be obtained from outside sources when completing a risk assessment e.g. an accredited water treatment company.