Respiratory physiologist. Haldane was born in Edinburgh into a notable family, which included evangelist brothers Robert (1764 - 1842) and James Haldane (1768 - 1851), the latter being John Scott Haldane's grandfather. He was the brother of politician Richard Burdon Haldane, Viscount Haldane of Cloan (1856 - 1928), and authoress Elizabeth Haldane (1862 - 1937). If this were not enough, Haldane fathered biologist J.B.S. Haldane (1892 - 1964) and authoress Naomi Mitchison (1897 - 1999).
Haldane was read medicine at the University of Edinburgh, graduating in 1884. His first position was at Queen's College, Dundee (then part of the University of St. Andrews). He transferred to Oxford, where is uncle was Professor in 1887, and lectured and researched in medicine. He established that it was the high concentration of carbon dioxide in the blood, not the low concentration of Oxygen, which regulated the breathing rate (1905). He demonstrated the effects of altitude and water pressures on respiration and devised a procedure for the decompression of deep-sea divers, permitting their safe return to the surface avoiding "the bends". Using his technique a valuable cargo of gold was recovered from the wreck of the Lusitania between 1917 and 1924.
He became an authority on the effects of pulmonary diseases on industrial workers and was appointed Director of the Mining Research Laboratory in Doncaster (1912). Haldane improved mine safety by demonstrating the toxic effects of carbon monoxide and the use of rescue equipment.
He founded the Journal of Hygiene, in which the first set of diving decompression tables were published in 1908, and his published works include Organism and Environment (1917), Respiration (1922) and The Philosophy of a Biologist (1936).
In 1936 Haldane went to Persia to investigate cases of heat stroke among the oil workers however, on his return to the cold of Oxford, he caught pneumonia and died.