LEV, Belfast, Dublin




In July, 1976 in Philadelphia an outbreak of pneumonia affected 221 people, killing 34. Many were members of the American Legion attending a convention in the Bellevue-Stratford Hotel. The causative organism, Legionella pneumophila, is widely distributed in nature and although positively identified and named only several months after the outbreak of the illness that gave the disease its name, legionnaires' disease, it has probably been causing infections in humans for hundreds of years.


Legionella species occur naturally in soil, rivers and lakes and have the ability to successfully colonise man-made water handling and storage systems, which often provide ideal conditions of nutrition and temperature for their proliferation. Legionella infection is not transmissible from person to person; it is caused by the inhalation of water aerosols containing the bacteria by susceptible individuals. The numbers of organisms required to induce infection is not known but will vary according to age, general health and other predisposing factors.

The potential for legionella to become a hazard to the health of large numbers of people is greatly enhanced by conventional water and air conditioning engineering methods as used in re-circulating cooling towers, evaporative condensers, showers, water storage and distribution systems and other aquatic systems such as whirlpool spa baths.

The single isolation of these bacteria from a water system does not mean that the disease will necessarily manifest itself but if the contaminated water becomes an aerosol the risk of human infection is greatly increased. Thus if man-made water systems produce jets, sprays or mists, as with cooling towers, showers and some types of humidifiers, it is important to minimise the chances of legionella colonising the water reservoirs, storage tanks and other aquatic systems serving them.


The Health & Safety at Work Act 1974 (HSWA) and Control of Substances Hazardous to Health Regulations (COSHH) include for the risks from hazardous micro-organisms, including legionella. Under the Regulations risk assessments and the adoption of appropriate precautions are required to be made. Furthermore, the Approved Code of Practice and Guidance L8 (Legionnaires' disease. The control of legionella bacteria in water systems), (the ACoP), sets out statutory requirements for dealing with such risk. The ACoP applies to the risk from legionella bacteria in any circumstances where the HSWA applies. In order to comply with their legal duties, as detailed in the ACoP, employers and those with responsibility for the control of premises should:

• Identify and assess sources of risk, (the ACoP dictates that persons responsible for undertaking the risk assessment need to have access to competent help and advice);
• Prepare a scheme for preventing or controlling the risk;
• Implement, manage and monitor precautions;
• Keep records of the precautions; and
• Appoint a person to be managerially responsible.

Proliferation of the bacteria typically occurs between 20 - 45˚C and is assisted by the presence of suitable nutrients present in Dirt, Sludge and Scale as well as conditions of poor water flow, stagnation or where dead legs occur in water systems. Employers are required to control the risk of exposure to legionella bacteria in accordance with Control of Substances Hazardous to Health (COSHH) Regulations. This is achieved by following the Approved Code of Practice L8: The Control of Legionella (Bacteria in Water Systems).

In general these require the employer to conduct the following:

• Identification & assessment of the risk
• Prevention or minimisation of risk from exposure to Legionella Systems for the management and selection,
• training and competence of personnel
• Record keeping of maintenance,
• cleaning and disinfection


The survey involves a visual inspection of all available pipework, cold water storage tanks, calorifiers / boilers / electric water heaters / other plant, all outlets to ensure compliance. An asset register is compiled, along with a simple schematic drawing. Prioritised recommendations will be produced in order to bring the system up to standard where applicable.