A hypocaust was a form of furnace used by the Romans for the purpose of heating baths and apartments; the word comes from the Greek hupo, meaning underneath, and kaio, meaning heat. The furnace was placed in a chamber beneath the floor, and the heated air and products of combustion were made to circulate round the walls and under the floor by means of hollow tubes or a hollow lining, and were also carried pipes to other rooms. The floors were supported by pillars to leave the necessary space.