Legionella Risk Assessment: Key Facts & Controls

Legionellosis is a collective term for diseases caused by legionella bacteria, including the most serious, Legionnaires’ Disease, and the similar but less severe conditions of Pontiac Fever and Lochgoilhead Fever. Legionnaires’ Disease is a potentially fatal form of pneumonia, and everyone is susceptible to infection. The risk increases with age, but some people are at higher risk, e.g. people over 45, smokers and heavy drinkers, people suffering from chronic respiratory or kidney disease, diabetes, lung and heart disease or anyone with an impaired immune system.

Legionella pneumophila and related bacteria are common in natural water sources such as rivers, lakes and reservoirs. They may also be found in purpose-built water systems, such as hot and cold water systems and spa pools. If conditions are favourable, the bacteria may multiply, increasing the risks of Legionnaires’ Disease, and it is vital to control the risks by introducing appropriate measures.

Legionnaires’ Disease is usually contracted by inhaling tiny droplets of water (aerosols) suspended in the air containing the bacteria, which is why showers and spa baths are at higher risk. There is no risk from drinking contaminated water.

The Need for a Risk Assessment

Since a change to guidance (known as the approved code of practice, ‘ACOP’), all systems require a risk assessment to assess legionella risk; however, not all systems will require elaborate control measures. A simple risk assessment may show that the risks are low and are appropriately managed to comply with the law.

Who Should Carry Out the Risk Assessment?

The ACOP requires a “competent person” to conduct the risk assessment”. Where risks are small, as, in many domestic properties, there is no reason why a landlord or agent cannot do the assessment themselves. The landlord or agent will be the ‘duty holder’ as they will be under the duty to ensure the property is safe and free from any substance that could harm the health of occupiers (including legionella).

The duty holder can nominate a “responsible person” who will undertake any general routine duties found under the risk assessment. Commonly the duty holder will appoint themselves as being the responsible person. If the landlord uses an agent, they may nominate the agent as the “responsible person”.

It is perfectly acceptable for the duty holder to ask a competent person such as a gas engineer when next carrying out a gas safety check to look for specific risks such as tanks in the loft, dead legs and checking temperatures.

Identifying the Risk

The risk assessment should identify and evaluate potential sources of risk and:

• the particular means of preventing exposure to legionella bacteria;
• or if prevention is not reasonably practicable, the particular means of controlling the risk from exposure to legionella bacteria.

Several factors create a risk of someone acquiring legionellosis, including (but not limited to):

• conditions suitable for the growth of the organisms, e.g. suitable water temperature (20°C–45°C)
• deposits that are a source of nutrients for the organism, such as sludge, scale, rust, algae, other organic matter and biofilms;
• a means of creating and spreading breathable droplets, e.g. the aerosol generated by showers or spa pools.

Any risks identified should have corresponding control measures in the risk assessment.

Void Periods

Void periods are a risk because water can become stagnant for a more extended period giving the bacteria time to multiply at the correct temperatures.

The risk assessment will need to show that procedures are in place to eliminate or reduce the risk.

Void periods could include periods when the occupiers are away for a protracted period, particularly over the summer, as in student lets. Water stored in the loft may be stagnant and warm enough to encourage breeding. The same may happen if occupiers do not use an ensuite for an extended time, but the heating keeps the water warm. Occupiers should be given information about precautions they should take if the supply is unused for a protracted period.

Recording the Risk

The assessor should enter all of the above and anything else referenced in the ACOP guidance onto the risk assessment form and any recommended remedial action. For example, the risk assessment could identify a water tank in the loft with no lid. This is an increased risk, and the evaluation should recommend a lid be fitted. The assessment can be further updated once the lid has been done, thus reducing the risk.

The ACOP guidance provides:

Once the risk has been identified and assessed, a written scheme should be prepared for preventing or controlling it. In particular, the written scheme should contain the information about the water system needed to control the risk of exposure. However, if it is decided that the risks are insignificant and are being properly managed to comply with the law, you may not need to take any further action. But it is important to review the risk assessment regularly and specifically if there is reason to suspect it is no longer valid, for example, changes in the water system or its use.

Health and Safety Executive

The Health and Safety Executive say risk assessments should be “simple, proportionate (to the risk) and effective”.

A good set of 4 rules to remember are:

Keep it Hot: Keep hot water hot, above 55 degrees if it is stored

Keep it Cold: Ensure cold water is stored below 20 degrees

Keep it Moving: Stagnant water is where it breeds, so ensure water does not sit for too long

Keep it Clean: Dirty systems give food to the bacteria so they can grow.