Forced-air furnaces are a common means of keeping homes warm in the area during our long, cold winters. They usually run on a daily basis for months on end, and few homes can go without them for even a few hours. Furnaces are comparatively simple forms of heating: using burners and heat exchangers to warm the air in a centralized location, then blowing the heated air through the home via a series of ducts.
The system is efficient and inexpensive, especially when you used models with the EnergyStar label, but like any system, it runs into trouble from time to time. When it does, homeowners need to move fast to get the problem treated, let their house turn into an icebox while they wait for repairs. The sooner one can spot the signs of a serious problem, the better.