A legionella risk assessment is undertaken to enable the person responsible for the control of the premises to comply with the guidance in the HSE document, “Legionnaires’ disease: The control of legionella bacteria in water systems – Approved Code of Practice and guidance (ACoP L8)” and BS 8580:2010: “Water quality - Risk assessments for Legionella control – Code of practice”. Survey information of the water system condition and other factors applicable to the requirements of the ACoP L8 has been recorded and recommendations are made in the report with reference to the relevant sections in the ACoP L8 document.
Implementation of recommendations as identified in the survey places a responsibility on employers and persons responsible for health and safety on the premises to prepare a scheme for preventing or controlling the risk from legionella bacteria. These requirements can be achieved by adopting a scheme of monitoring in conjunction with a regime of preventive maintenance. Records of all activities relating to the control regime must be kept.
To identify and evaluate areas of concern and thereby enable a decision to be made with regard to the health and safety risks associated with water systems within a building.
Legionnaires disease is the most well-known and serious form of diseases known as Legionellosis. Legionnaires disease is a potentially fatal form of pneumonia (infection of the lower respiratory tract) caused by the legionella bacteria. Legionnaire‟s disease is normally contracted by inhaling water aerosol/droplets contaminated with legionella bacteria. Legionella pneumophila is one species and is commonly associated with disease outbreaks. Legionella pneumophila can also cause short feverish illness without pneumonia known as Pontiac Fever and Lochgoilhead Fever.
Legionella bacteria are common and can be found in environmental water sources. Legionella bacteria in water provided with an ideal temperature range 20oC – 45oC and nutrients are most likely to proliferate. Legionella will survive at temperatures below 20oC but is considered to be in a dormant state with no growth activity. The bacterium does not survive temperatures maintained consistently at 60oC or above.
Research and investigations indicate that the occurrence of legionella contamination is greatest in manufactured water systems such as water cooling towers, evaporative condensers, hot and cold water services, water spray humidifiers, air washers, spa baths and pools etc. Sediment, scale and organic materials present in water systems, can provide nutrients and give protection for legionella.
Legionella have been shown to colonise certain types of water fittings, pipe work and materials used in the construction of water systems. The presence of these materials may provide nutrients for legionella and make eradication difficult. Other organisms in water systems such as bacteria, amoeba and algae can provide a suitable nutrient and habitat in which legionella can survive and multiply.
The formation of biofilms within a water system is undesirable and may provide a protective harbour and favourable conditions for legionella proliferation. Incorporation of legionella in biofilms and in enclosures within protozoa can protect the organisms freely suspended in water.
Legionnaire‟s disease is most commonly caused by the inhalation of water droplets/aerosol contaminated with the legionella bacteria. It is therefore important that systems susceptible to colonisation by legionellae and which incorporate a potential means for creating and disseminating water droplets/aerosol should be identified and the risk they present should be assessed. This identification and assessment is required under the relevant Approved Code of Practice & Guidance (ACoP L8) "the control of legionella bacteria in water systems‟.
The assessment must be completed for routine system operation and use and also for circumstances such as breakdown, abnormal operation, commissioning or other unusual circumstances.
Once the assessment has been completed a monitoring regime can be implemented to prevent or control the risk. The monitoring regime will be based on a sound knowledge of the varying levels of attention required by the differing risk sources within the building.
The assessment takes account of:
It should be noted that a legionella risk assessment is valid for a period of two years. However there is a requirement for the assessment to be updated when the original assessment is no longer valid due to circumstances such as:
Once a risk has been identified and assessed, a scheme should be prepared for preventing or controlling it. The risk is heightened when conditions are not monitored and controlled and legionella is allowed to proliferate. The scheme should be implemented together with planned preventative maintenance in line with that contained within the general recommendations of this report. This will meet the requirements of ACoP L8 and “prepare a scheme for preventing or controlling the risk”.
Under general Health & Safety Law employers or persons in control of premises (e.g. a Landord) have a responsibility to ensure that the risk from exposure to legionella is properly controlled. Those who could be exposed may include guests, staff, customers and contractors
Risk assessment/Audit records must be kept for five years.
Health & Safety Executive publication
Legionnaires’ disease. A guide for employers
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