Companies 2 and 11 were dispatched for an odor of smoke in a residence. Engine 23 arrived on scene and established command, followed by Ambulance 28, Chief 2-2, Quint 11 and Engine 111. Command was passed to Chief 2-2 upon his arrival and crews from Engine 23 and Quint 11 investigated all levels of the structure. Crews encountered a smell of smoke upon entering the structure and were able to isolate the source to the furnace. While crews from Engine 23 and Quint 11 investigating, personnel from Engine 111 investigated all exposures, checking for any fire extension. The crew run Engine 23 ran a test of the furnace and observed visible fire. They immediate shutdown the furnace and extinguished the fire and removed the power source. The structure was ventilated and crews returned.