Some of the smoke that flows up your chimney condenses and becomes creosote that sticks to the flue. Creosote is a hard tar-like substance that builds up over time. As the coat of creosote thickens, it increases the chance of a fire breaking out in the chimney.
When a chimney fire burns, extremely high temperatures are created that can cause cracks to form in the flue. These cracks can pose a serious health threat to your family because they allow carbon monoxide that would normally vent up the chimney to be drawn back into the home. Carbon monoxide is an odorless colorless gas that can be lethal.
To prevent chimney problems, you should have your chimney professionally inspected and cleaned yearly. The National Fire Protection Association has adopted these levels of inspection to create code NFPA 211, Standard for Chimneys, Fireplaces, Vents and Solid Fuel Burning Appliances. This is the standard that certified chimney sweeps use when cleaning chimneys:
· Level I Inspection: Recommended when the chimney is easily accessible and the homeowner is planning to maintain it as is. In this inspection, a certified chimney sweep verifies that the chimney structure is sound and that the chimney is free of obstructions and combustible deposits such as creosote.
· Level II Inspection: If the homeowner has added a new home heating appliance or changed the type of fuel being burned, the chimney requires a Level II inspection. This inspection level may also be required after the sale of a property or an event that is likely to have caused damage to the chimney. This inspection includes the Level I inspection plus the inspection of accessible portions of the attics, crawl spaces and basements. It may also include a performance test, such as a smoke or a pressure test, and an interior chimney video inspection if recommended.
· Level III Inspection: When a Level I or Level II inspection suggests a hidden hazard and the evaluation cannot be performed without access to concealed areas, a Level III inspection is recommended. This type of inspection confirms the proper construction and condition of concealed portions of the chimney structure and the flue. Level III inspections are also necessary when investigating an incident that caused damage to a chimney or building.
In addition to yearly inspections, you may also want to consider a metal chimney liner. They protect the chimney from corrosion as a result of the byproducts released during combustion. Liners are made from stainless steel or aluminum and can be used to repair existing chimneys. They are U.L. tested, and if properly installed and maintained, they are safe and durable. Stainless steel is used in chimneys for wood burning, gas, or oil applications. Aluminum is only used for certain medium efficiency gas applications. High temperature insulation is required to be used in conjunction with the liners to ensure safety.