This guidance is intended for the benefit of all those involved in the operation and maintenance of engineering services. It is an update of the original version of this document which was published in 2000 as Guide to ownership, operation and maintenance of building services. Principal areas of revision relate to legislation that has occurred since the first edition, the impact of climate change and subsequent need to address energy use and building performance. The intention has been to identify current good practice and address topics of particular interest and relevance to those involved at all levels in engineering services maintenance. This includes designers, manufacturers, installers, maintainers, building owners, occupiers and operators, professional advisers and specialist providers. It is not expected that the reader will read the publication from cover to cover; rather that it will be used for reference and guidance as needs arise.