Praefurnium
The praefurnium (plural: praefurnia) was the furnace room that provided heated air for use in a hypocaust system, the underfloor heating created by the pumping hot air into a cavity beneath the floor of a room, supported by brick (or sometimes stone) pillars. These were primarily used in conjunction with Roman bathing complexes in order to heat the warm and hot rooms of the baths, but could be used for the heating of living areas in colder climates. The word is derived from the Latin term for an oven, furnus, also the derivation from the English word ‘furnace’.
Heat was achieved in the praefurnium with a wood fueled fire. The praefurnium was not an actual part of the course of the baths, but was rather part of the service areas inaccessible to the patrons of the baths. It was typically situated closest to the caldarium in order to provide it with the hottest air, as the temperature would dissipate somewhat as it traveled to other rooms such as the tepidarium, which did not require the hottest air. Depending on the heating needs of the baths, more than one praefurnium may be present.
