The heaters were kept burning by attendants, know as "potato bugs" who accompanied the cars to their destinations, usually Boston or New York. Each potato bug tended four or five cars and serviced the heaters whenever the trains stopped for a sufficient time period to get the heaters taken care of. They rode with the train crews between stops and after reaching their destinations returned to Mane on passenger trains at the railroads expense. Source: "The Bangor and Aroostook, 1891-1966" published in February, 1966 by the railroad. On visits to Maine I have seen a few of these heaters for sale at antique stores and some have been known to have seen service heating ice fishing shacks.