This document specifies requirements for technologies that enable on-site detection and quantification of Legionella spp. and L. pneumophila using a quantitative polymerase chain reaction assay (qPCR). It specifies general methodological requirements, performance evaluation requirements and quality control requirements. This document is intended to be used by manufacturers of these technologies so that they produce detection systems that end users may operate safely and effectively. End users will be guided by this document to adhere to manufacturer’s instructions, ensure user competency and perform the necessary controls. NOTE 1 For the responsibilities of the manufacturer and the end users see Annex A. Technical details specified in this document are given for information only. Any other technical solutions complying with the performance requirements are suitable. NOTE 2 For validation and performance requirements, see Clause 9. This document is intended to be applied in the bacteriological investigation of all types of water (hot or cold water, cooling tower water, etc.), unless the nature and/or content of suspended matter and/or background microorganisms interfere with the determination. This interference can result in an adverse effect on both the detection limit and the quantification limit. The results are expressed as the number of genome units of Legionella spp. and/or L. pneumophila per millilitre (or litre) of sample. Although the method described in this document is applicable to all types of water, some additives, such as chemicals used for water treatment, can interfere with and/or affect the sensitivity of the method. The qPCR methods do not give any information about the physiological state of the Legionella. However, there are on-site qPCR methodologies which are able to distinguish intact bacteria from free DNA. In such cases, validation of the method shall include satisfying this performance requirement.