WHY DOES MY OIL FURNACE CHIMNEY FLUE NEED CLEANING?
The incomplete by-product of combustion of fuel oil is unburned carbon and sulphur - called oil soot. Oil soot accumulates on the walls and at the base of the chimney, which should be inspected and cleaned annually by a CSIA certified chimney sweep.
Most homeowners are unaware that the chimney venting system for the furnace needs maintenance. Most find out after the chimneys are clogged, or the interior collapses, that they need a chimney technician. It is usually too late for a routine cleaning at this point and homeowners are stuck with emergency service call costs and blockage removals or repairs in order to get the heat and hot-water turned back on. This could be avoided by routine maintenance and inspections of the furnace chimneys.
The best time of the year to clean an oil chimney is in the spring time, after the heating season. During the winter, the oil furnace is subjected to long running cycles, which will produce oil soot that may adhere to the sides of the chimney. The accumulation of these soot deposits will fall to the base of a masonry chimney, or directly into the top of the oil furnace if a metal chimney is located directly above the appliance. It will restrict the flow of flue gases, which consist mostly of nitrogen, carbon dioxide, and water vapor. Combustion will also produce carbon monoxide (which is a dangerous gas when not vented properly), which will spill back into the house instead of going up the chimney when the chimney base is not properly cleaned.
A big misconception on many homeowners' part is that the oil service company takes care of the chimney. The oil burner company may shovel out the base of a brick chimney and brush out the connector pipes, but they will not clean the chimney. Most furnace technicians fail to mention anything about the chimney leading homeowners to believe everything is fine. Some oil furnaces service men even tell the homeowner that the chimney is OK without inspecting the entire chimney, which includes going to the roof and inspecting the interior as well as the exterior masonry (if applicable), flashing, chimney cap, etc.
The National Fire Protection Association 211 codes state that "chimneys must be inspected and cleaned as necessary annually" - just like the oil service man services the furnace annually, so should the chimney system be serviced annually.
Many homeowners also may not be aware that the chimney's interior, when not maintained, will decay and break down - just like neglecting your teeth and not having them checked annually may result in cavities. (Or if you don't change the motor oil in your car for 50,000 miles, you can be sure something in the motor will break.) It's the same thing with your chimney. As stated earlier, the incomplete by-product of combustion is soot, which contains carbon and sulphur. Sulphur, when mixed with rain water (from a missing rain cap) or moisture from the flue gases themselves is absorbed into the flue tile and starts a deteriorating process called flaking or spalling. Just like tartar on your teeth, annual brushing will remove these soot deposits and keep the deterioration process to a minimum.
In metal chimneys, the interior lining is made from stainless steel, which will not rust, but will corrode from the oil soot's sulfuric acid reaction. This corrosion makes small pinholes, which will ruin the integrity of the liner, which will not be able to hold the by-products of combustion. When a clay lining in a masonry chimney flakes or a metal chimney's insides corrode, they are unable to contain the heat and the flue gases, thus creating a potential fire and health hazard.
Annual inspection and cleaning by a CSIA certified chimney sweep will find these problems and give you recommended corrective actions. When the sweep arrives at your home to do the annual inspection and cleaning of the oil chimney, he will set up his equipment (vacuum, etc.), remove and inspect the connector pipes (the pipes from the oil furnace to the chimney) - careful as not to spill soot into the home. The chimney connector will be cleaned and closed off so that when the chimney is swept, no soot will enter the home. An inspection of the exterior chimney will be made, the chimney swept, and then the interior of the chimney inspected for deterioration and soundness. The sweep completes the exterior work and next returns inside and removes the soot that was brushed down the chimney. When the connector pipes are reinstalled, the furnace will be restarted and checked for proper chimney draft. (info provided in part by John Pilger -Vice President of New York State Chimney Guild).