How large should the room be, to place a cremation furnace? A minimum of 65 square meters of space is needed to place a new cremation furnace with cremation filter system inside a crematorium. This is for one cremation furnace. When you want to place more furnaces next to each other then we advice to reserve some extra square meters around the cremators. This is wise to do as this is the best solution for maintaining on the cremation ovens, for a proper periodic maintenance.