As an employer or person with the responsibility for the control of premises you have a legal obligation to manage the risk of Legionnaires disease. Legionnaires disease, also known as legionellosis, is caused by the inhalation of airborne droplets which contain legionella bacteria. These airborne water droplets or aerosols are often invisible and are generated by simply running a tap or using a shower. Infection by legionella bacteria can result in pneumonia. Symptoms include a cough, shortness of breath, high fever, muscle pain and headaches. Legionnaires disease has a fatality rate of about 12%.
Who is at risk?
Legionnaires disease can affect anybody, although males over 50 years are more susceptible. The risk of contracting Legionnaires disease is also increased from smoking and people with an existing pulmonary illness.
Where is the bacteria found?
Legionella bacteria are found widespread in natural water sources. However, legionella bacteria can also colonise any hot and cold water system. Colonisation occurs when water is allowed to stagnate and either the hot or cold water temperature is between 20°C and 45°C. Insufficient cleaning also allows the accumulation of sludge, rust and scale which will support the growth of the legionella bacteria.
What precautions should you take?
Prevention of Legionnaires disease relies on applying control measures to minimize the growth of the legionella bacteria and creation of aerosols. These measures include:
- Knowing your water systems and removing any redundant pipework, keeping pipe lengths as short as possible which could allow water to stagnate within;
- Nominating a competent person to manage the water system;
- Flushing irregularly used outlets such as showers, toilets and running taps for 10 minutes weekly to reduce water stagnation, ensuring there is good ventilation when carrying out this task; Routinely cleaning shower heads and taps; removing any lime scale, mould or algae growth;
- If cold water storage tanks are present, ensure they are fitted with a tight lid to prevent water being contaminated, insulated so cold water is kept below 20°C and the tank is annually drained, treated and inspected for damage;
- If water is heated and stored in a hot water cylinder, ensure that the hot water system is regularly serviced, drained, cleaned and the hot water is set to a temperature above 60°C;
- Monitoring the water temperatures of the cold and hot water supply from the tap furthest / nearest to the water boiler and furthest /nearest to the cold water tank;
- Circulated cold water should be below 20°C and hot water above 50°C.