Health and Safety Executive (HSE), Safety in the installation and use of gas systems and appliances, Gas Safety (Installation and Use) Regulations 1998, Approved Code of Practice and guidance, Draft Version of L56 (4th ed., 2013), Glossary Merseyside, England, UK 2013. SBN 978 0 7176 6419 1, http://www.hse.gov.uk/aboutus/meetings/hseboard/20 13/250913/psepb1389-b.pdf, (Hlth and Sfty - Brit) {723}