This British Standard gives recommendations and guidance on the assessment of the risk of legionellosis presented by artificial water systems. It is applicable to any undertaking involving a work activity or premises controlled in connection with a trade, business or other undertaking where water is used or stored in circumstances that could cause a reasonably foreseeable risk of exposure to legionellae and contracting legionellosis. The standard is applicable to risk assessments being undertaken on premises, plant and systems for the first time, and to review and audit where a previous assessment has been undertaken and where control measures might have been implemented. This British Standard does not give recommendations for: the assessment of the risk presented by natural waters, including rivers, lakes, ponds, waterfalls, caves, dew ponds or natural recreational facilities, such as boating lakes; or the preparation of the scheme of control for the risk systems identified. AnnexA gives general guidance on the assessment of systems, while AnnexB to AnnexE give guidance on the assessment of specific types of system. AnnexF gives an example checklist for the assessment of a particular system (spa pool). A list of equipment that might be used by a risk assessor is given in AnnexG, and AnnexH gives guidance on the production of schematics. NOTE The guidance in AnnexA to AnnexE is not intended to be exhaustive; merely to highlight some of the more common issues associated with particular systems to be considered as part of a Legionella risk assessment. Where appropriate, these annexes contain references to publications that give more detailed information about these systems.