The Coal Hill School boiler room in 1963 contained a pre-World War II "clanking and spitting" furnace and boiler, on which heating throughout the school was dependent. The furnace had to be kept on overnight to stop the pipes from freezing in the winter.
On 2 April 1963, Susan Foreman, John Brent and Gillian Roberts made shelter there, after spending the night at school, and Susan wrote in her diary. Later, trying to warm up after an attack by the Cold, Susan Foreman actually found the boiler room too hot, but they stayed there anyway. (PROSE: Time and Relative)