Barrier systems for control of Legionella

Article published in the Regulator issue 1:2015

Following a recent planned inspection, NOPSEMA made recommendations to a facility operator regarding the need for an effective management framework to ensure the periodic inspection, maintenance and monitoring of the drinking water system. One of the purposes of the recommendations was to ensure a robust system exists to prevent pathogens, such as Legionella, multiplying in the water system.

The bacterium, Legionella, is found naturally in fresh water systems. Legionella have also been isolated from artificial water systems such as evaporative condensers, hot and cold water systems, shower heads, emergency showers and treated sewage in which the organisms have been able to multiply because of warm conditions and the presence of nutrients. These water systems and conditions exist on offshore facilities. 

The occupational respiratory disease known as Legionnaires’ disease (Legionellosis), commonly caused by the bacterium, is a serious illness (lung infection) resulting from inhalation of aerosolised water which contains the bacterium. The Energy Institute’s Occupational Health and Hygiene Committee found it relevant to provide the oil and gas industry with appropriate guidance on how to manage the control of Legionella in its facilities following the 2012 outbreak of Legionnaires’ disease in Edinburgh, Scotland. The published guidance, entitled Legionellosis risk management and Legionella control – Guidance for oil and gas facilities, offshore platforms and refineries, is available at

Prevention of Legionnaires’ disease requires the formal identification and assessment of risk, by a competent person, from sources known to cause the disease, in the water systems and associated equipment on an offshore facility. The formal risk assessment should document the multiple barrier systems employed on the facility to prevent, detect and control Legionella.

The barriers could include:

• identifying a competent  and responsible person for inspection, maintenance and monitoring the water system

• performing periodic inspection, maintenance and monitoring on the water system e.g. filters, temperature, flow rates, disinfection, microbial testing • recording  results of the inspection, maintenance and monitoring performed

• performing a periodic audit of the water system. Operators are encouraged to monitor, audit and review the multiple barrier systems which are used on the facility to ensure a robust system exists to prevent pathogens such as Legionella multiplying in water systems.