Born in London, Mapleson was educated in Amersham, Buckinghamshire, where his family moved in 1937. At the advice of his physics and mathematics teacher he studied physics at the University of Durham, graduating in 1947. After two years National Service in the RAF he returned to Durham to take his PhD before becoming a research assistant/lecturer in the Department of Anaesthetics of the Welsh National School of Medicine in Cardiff where the head of department was William Mushin.
Mapleson quickly came to the attention of anaesthetists when his examination of the conditions needed to eliminate rebreathing in the five anaesthetic systems was published. Within a couple of years the systems were often referred to by his labels.
Mapleson’s main research interests were in the pharmacokinetics of inhaled anaesthetics and the functioning of automatic lung ventilators and he published over 100 research papers and other publications. In 1973 he was recognised by receiving a personal chair in the physics of anaesthesia in Cardiff.
A founder member of the British Anaesthetic Research Society, Mapleson officially retired in 1991, although he still spends two mornings a week teaching and advising on research in the department.