Starting this evening my Janitrol furnace is making an exceptionally loud bang. It has repeated the bang every time since at startup. I have disengaged the unit, cleaned the filters and cleaned out the unit, checking the venting for obstructions (haven't seen any). It's late and pretty cold out here in the Chicagoland area. Don't have a lot of options for staying elsewhere tonight, any suggestions to limp until morning?

Sorry noise could be a number of things, if you can isolate better for us where and when you hear it, maybe we can get a better idea.