What is Legionnaires’ Disease?
Legionnaires’ disease is one of a group of diseases collectively known as legionellosis. There are thirty-seven different species of bacteria associated with legionellosis, the most serious being Legionella pneumophila, which if infected with can result in pneumonia and other potentially life threatening effects.
Where does it come from?
Legionella organisms are widespread in natural water sources such as rivers, lakes, mud and soil, but can also colonise man-made recirculating hot and cold water systems such as storage tanks, calorifiers (hot water tanks), air conditioning systems and cooling towers.
How do you become infected?
Legionellosis is normally contracted by inhaling airborne droplets that contain Legionella bacteria, which first require conditions that permit growth of the organism and involve the creation of droplets, which can be inhaled.
Legal Requirements for businesses
(1) General duties under the Health and Safety at Work etc. Act 1974 and the Control of Substances Hazardous to Health Regulations 2002 extend to the risks from Legionella arising from work activities.
(2) The HSC Approved Code of Practice L8: The control of Legionella bacteria in water systems provides guidance on the standards required to address the legal duties relating to Legionella risks. The Code of Practice applies whenever water is stored or used in a way which may create a foreseeable risk of Legionellosis, including;
o Water systems incorporating a cooling tower
o Water systems incorporating an evaporative condenser
o Hot and cold water systems
o Humidifiers and air washers that create a spray of water droplets and in which the temperature is likely to exceed 20°C.
o Spa baths and pools in which warm water is deliberately agitated or recirculated
Action Required
The principles of a Legionella control system are:
- The identification and assessment, by a competent person, of legionella risks.
- Preparing a scheme to prevent and/or control the risks of legionella.
- Implementation and management of the control measures.
- Keeping relevant records, e.g. temperature checks, system schematics.
- Appointment of a competent person to manage to control measures. (Responsible Person)
Typical controls for hot & cold water systems
The main way to control Legionella is by keeping water temperatures outside the range in which the bacteria readily survive which is 20 to 45C. You should aim to store hot water above 60°C to reach the tap above 50°C. Cold water should be stored and distributed below 20°c.
Monthly monitoring of the temperatures of hot and cold water at sentinel taps (the first and last tap in the system) is recommended covering annually a representative number of the remaining taps on a rotational basis. Temperatures for taps fitted with thermostatic controls (TMV’s) should be taken at the pipe as close to the TMV as possible. TMV’s should be fitted as close to the outlet (tap) as possible to minimise growth opportunities for Legionella to grow.
Infrequently used taps and other outlets should be identified and flushed through weekly. Shower heads should be dismantled, cleaned and descaled quarterly.