A puffback is a misfire in the furnace that, at its worst, can send soot throughout your home, requiring expensive cleaning and restoration in addition to repairs on your heating system. While rare, the consequences are severe enough to learn what a puffback is and how you might prevent it.
A puffback can happen when an oil burner doesn't ignite immediately and vapors are allowed to build up before ignition, resulting in an explosion similar to the backfiring of a car. Buildup of debris can also create an excessive explosion at ignition. In either case, the explosion can shoot soot and debris through the furnace or boiler's exhaust system and into your home. If you have a forced air system (a hot air system as opposed to a hydronic, or hot water, system), the problem will likely be worse as the heating ducts can spread the soot into every corner of your home, with the same efficiency that they spread heat. A puffback can be a chronic problem, with each ignition sending forth a small amount of soot that slowly accumulates on ceilings, carpets, or baseboards, or it can be a single sudden event that sends a large amount of soot through the heating system.