Legionella is a bacteria that grows in water. It was first identified after an outbreak at an American Legion Convention in Philadelphia in 1976. Legionnaires’ disease is usually contracted by inhaling the Legionella bacteria in tiny droplets of water.

Legionnaires’ Disease is a form of pneumonia and fatal in approximately 12% of the 200-250 cases reported in the UK every year. Certain groups are more susceptible to contracting Legionnaires’ disease, for example men, those over 45 years old, smokers, alcoholics, diabetics and those with cancer or chronic respiratory or kidney disease.

Legionella appear to grow best in water between 20 – 45°C. For this reason it is vital that systems which have the potential to grow Legionella are closely monitored and treated. Unfortunately these systems are extremely common and present in most companies – including hotels and hospitals.

Cooling towers pose a significant risk and, as a result, every company with a cooling tower must register with the local council. This is due to the fact that cooling towers process water at a temperature within the 20 – 45°C bracket and produce an aerosol. There have been many Legionella outbreaks in the past which have been traced back to a cooling tower (one of the most well-known cases was the Barrow incident, which you can read more about here). More information on exactly what a cooling tower is and how to treat them will follow.

Hot and cold domestic water systems must also be closely monitored and treated. Taps, showers, water tanks and other hot or cold water outlets in any company are at risk if not correctly maintained. For example, showers consistently run within the 20 – 45°C bracket and water is left in the pipework to the shower and the showerhead itself may be left to stagnate. This presents a Legionella risk and if the shower is not used for a period of time they can be a significant threat. More information on treating hot and cold water systems will follow.

Legionella risk assessments must be conducted under ACoP L8, the guidelines for employers on Legionella and Legionnaires’ disease. These must be carried out on any open evaporative cooling system and any domestic system.


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