Legionella Risk Assessment
The first step in any risk management process is production of a professional risk assessment. Legionella management is no different and as required by the HSE’s Approved Code of Practice (ACOP L8), since the removal of the 300 litre limit, a written down risk assessment is now required for all commercial buildings with a water supply employing 5 or more people.
As set out in the guidance, the person on who the statutory duty falls is required to have ‘access to competent help in assessing the risks’. This involves the engagement of an external water consultant to produce a risk assessment. The risk should;
- Identify and evaluate all potential sources of risk
- A means by which exposure to bacteria can be prevented (where possible)
- Where prevention is not possible, a means by which the exposure can be controlled.
What does the risk assessment process involve?
A Legionella Risk Assessment involves a trained engineer visiting a premises and making an objective assessment of the water system’s potential to be colonised by Legionella bacteria and the various factors favourable for their continued growth These factors include;
1. Temperature – Legionella require a range of between 20 – 50oC to multiply
2. Nutrients – much like any other living organism the bacteria need a source of food. In a water system this takes the form of sludge, scale, rust and even other bacteria
3. Aerosol Creation – an assessment of the type of water services present to judge the likelihood of an aerosol being created.
4. Personnel – it is well known that males are 3 times more likely than females to catch Legionniare’s disease and the elderly and immuno compromised are more at risk.
5. Potential for Stagnation – stagnant water can provide an excellent breeding ground for bacteria and often where slow moving water is found the temperature is raised.
In completion of a risk assessment all areas of the water system are inspected including loft spaces and void areas however there is no disruption to the water supply and this can usually be completed during usual hours.
Following the on site assessment, a report is produced together with remedial recommendations and basic schematics drawings. In general premises fall into one of two categories;
1. No reasonably foreseeable risk for exposure to Legionella. In this instance a site will be deemed ‘low risk’ and no further measures / assessment are necessary. This would usually only apply to systems without any stored water i.e. cold water storage tanks and / or hot water cylinders.
2. Reasonably foreseeable risk of exposure to Legionella. This is usually the case where a cold water storage tank and / or hot water cylinder are present. It is then necessary to take further steps to mitigate the ongoing risk.
Where there is a foreseeable risk it is necessary to have some form of ongoing Legionella Management.
How often should I review my risk assessment?
A full re assessment should be completed every 2 years but in addition to this;
change to plant / water system or its use
change to use the of the building
new information about risks / control measures
tests indicate control measure are ineffective
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