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 and spa pools, such as hot and cold water systems. If conditions are favourable, the bacteria may multiply, increasing the risks of Legionnaires' Disease, and it is crucial 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 inspection 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.

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. appropriate 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;
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.

Recording The Risk

The responsible person 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 that a cover be fitted. The responsible person can further update the assessment once the cover 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 maintain the risk from 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 essential 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.

Legionella Risk Assessment Template