While the UK has an enviable safety record in the management of medical gas systems, it is only via strict adherence to the four tenets - 'continuity, adequacy, identity, and quality' - embodied within Health Technical Memorandum 02-01: 2006 - 'Medical Gas Pipeline Systems' (MGPS) that we can be certain that patients will not be harmed by these systems. So says Geoff Dillow, a former training head at the forerunner to today's Eastwood Park, the National Centre for Hospital Engineering, and co-author of the HTM, who has over 35 years' professional experience in assessing medical gas systems for compliance. In the first of four HEJ guidance articles on 'Managing Medical Gas Pipeline Systems' planned for coming months, he examines the critical role of the MGPS Permit to Work System (PTWS), and describes the parts played by those involved in its implementation and day-to-day management.