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Control of legionella bacteria in hot and cold water systems

Health and Safety Executive - Safety Notice
Department Name: Hazardous Installations Directorate (Offshore Division)
Bulletin No: HID 5-2010-1
Issue Date: 21 May 2010
Target Audience: Offshore Industry
Key Issues: This notice is to remind duty holders of the requirement to:
  • identify and assess sources of risk for legionella bacteria in hot and cold water systems, and
  • take steps to prevent or control the risk by putting adequate controls in place and maintain and monitor those controls to ensure effectiveness


This notice is to remind duty holders of the requirement to:

This follows recent inspections of offshore installations, which have identified significant failings in the control of legionella bacteria in hot and cold water systems and resulted in formal enforcement action being taken against the duty holders concerned.


Legionnaires' disease is a potentially fatal form of pneumonia caused by the bacterium legionella pneumophila. The predominant route of infection is inhalation of contaminated aerosols. On average there are approximately 300 - 500 reported cases of Legionnaires' disease each year in the UK. One case has been reported for offshore in the last ten years but not everyone exposed will develop symptoms and those that do not develop the full blown disease may present with mild flu like symptoms. Although the risk of contracting the disease through exposure offshore is low; legionella bacteria are known to colonise and multiply in hot and cold water systems on offshore installations.

Action required:

Duty holders are required to assess the risks from legionella bacteria within their potable water systems and put in place a scheme to prevent or control the risk. In relation to offshore installations the actions required will include, but are not limited to, the following:-

Assessing and managing the risk

Preventing and controlling risk

Relevant legal documents:

The relevant legal requirements are:


You can find more relevant information in the following publications:

  1. Legionnaires' disease. The control of legionella bacteria in water systems. Approved Code of Practice and guidance L8 Third Edition HSE Books 2000 ISBN 978 0 7176 1772 2
  2. Control of substances hazardous to health. The Control of Substances Hazardous to Health Regulations 2002 (As Amended) Approved Code of Practice and guidance L5 Fifth edition HSE Books 2005 ISBN 978 0 7176 2981 7
  3. UK Offshore Operators Association (now UK Oil and Gas) Guidelines for Environmental Health for Offshore Installations 2007
  4. See also Legionnaires' disease

Further information:

Any queries relating to this notice should be addressed to:

OSD 5.4
Health and Safety Executive
Hazardous Installation Directorate
Offshore Division
Lord Cullen House
Fraser Place
AB25 3UB

General note:

Please pass this information to a colleague who may have this Product/Equipment or operate this type of system/process.