On Monday, February 10, 2013 a local professional chimney sweep found a nest that was built between chimney pipe and the wood chimney chase for a manufactured fireplace in Kansas City, Missouri. The nest and wood was charred, which means that the nest was trapping heat in an area that needed to be clear of obstructions. Heat chemically changes the structure of wood over time and lowers the ignition point. Where wood normally ignites at 500 degrees, wood exposed to heat over time may ignite at only 180 degrees or lower. In this case, the homeowners were lucky to have had service done to their chimney when they did or it would have gone unnoticed and eventually caused the wood chimney chase to catch fire.
Birds love to build nests inside and on chimneys where they have some protection from the elements. Unfortunately, nests are built with flammable dry twigs and other materials that can easily catch fire and cause a chimney fire or house fire.
Chimney swifts are especially drawn to dark, cool masonry chimneys and build their nests with mud and twigs on the side walls of flues and smoke chambers. In the U.S., the Chimney Swift is protected by the Migratory Bird Treaty Act of 1918. Neither birds nor nests can be removed from chimneys without a federally-issued permit. Other birds build nests on the smoke shelf or damper. All nests are flammable and are a fire hazard.
Unfortunately, the Migratory Bird Act prevents homeowners or chimney sweeps from removing nesting birds of any type inside chimneys, and substantial fines may apply per occurrence.
Homeowners can prevent the entry of birds into masonry chimneys by installing a masonry chimney cover with bird guard screen on top of the flue. A chimney cover serves dual duty by keeping rain out of the flue as well, which deteriorates mortar joints inside the flue and can cause costly damages.
According to the National Fire Protection Association, over 14,000 house fire occur each year due to improper maintenance or construction of chimneys and fireplaces. A portion of those fire are due to flammable materials in the flue (creosote) which ignite by a spark or flame.
The NFPA recommends annual inspection of all chimneys and flues by a professional chimney sweep.