My furnace was working intermittently. It would fire up but the flame would blow out. This happened sometimes, while other times it would ignite, stay lit and heat the house. The representative from Crystal Heating was able to come within a day of calling and repair the problem (gas jets needed cleaning) and also give the furnace a seasonal tuneup. He worked very quickly for a reasonable cost. Two months later, during very cold January temps, the furnace is working well and I have had no further issues, since the repair.