Lewis Short
praefurnĭum (noun N) : prae-furnus.
* The opening of a furnace, the door by which fuel is admitted: si uno praefurnio coques,Cato, R. R. 38, 1.
* The heating-room, or hot anteroom of a bath, = προπνιγεῖον, Vitr. 5, 10, 2; 7, 10.
Charlton T. Lewis, Charles Short, A Latin Dictionary