Prevention of legionella

Another Approved Code of Practice that has been through the consultation process is L8, Legionnaires’ disease: The Control of Legionella Bacteria in Water Systems. HSE has revised the document, removing the technical guidance which has now been published separately online. The previous technical guidance was 13 years old and significantly out of date.

The information is aimed at duty holders including employers; those in control of premises; and people with health and safety responsibilities for others, and was one of several identified for review and revision; consolidation; or withdrawal, in line with a recommendation by Professor Ragnar Löfstedt in his report ‘Reclaiming health and safety for all’. A key change is some guidance being assigned Approved Code status, to clarify legal requirements where there is an accepted industry method of compliance. The revised L8 document is available at

Revised additional guidance (HSG274) gives practical advice and is in three parts:

  • Part 1: The control of legionella bacteria in evaporative cooling systems
  • Part 2: The control of legionella bacteria in hot and cold water systems – Interim guidance (please note that this is extracted from the previous edition of L8. As this section is under review, this is interim guidance and will remain in place until the review and revision of the hot and cold water section is complete).
  • Part 3: The control of legionella bacteria in other risk systems

The complete hard copy edition of HSG274, including revised guidance on hot and cold water systems, and a revised online version of Part 2, will be published later this year. See

The final version will be published later this year.

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