We bought a house last year which has a Cannon K38 gas heater. We used it last year but it is obviously in need of a service or something (!) as the ceilings have black marks from it. We believe it is not venting properly and are wondering if it is worth getting serviced. We are intending to renovate in about a year so would rather keep using this winter and then replace it with the renovation. Any experts on this kind of heater?