Foul Smelling Smoke From a Chimney

The safest chimneys contain a strong cap and screen.

Constant use of wood-burning stoves and fireplaces is common during times of rising fuel costs. As long as a fireplace, furnace or stove is kept clean, fire and other problems are kept at bay. However, you may sometimes experience foul smells coming from your chimney. While routine sweeps will keep chimneys clean and safe, some agents may return and bring smells with them.

Mold

Leaky chimneys will eventually cause mold to grow. The most common way mold grows is for water to leak from the outside and settle inside where it's undetected. As mold grows, it can cause breathing problems and foul odors. It is important to seal chimneys thoroughly so mold doesn't form when a chimney is not in use.

Creosote Buildup

Creosote is a gummy, wood-burning byproduct. It forms on the interior walls of chimneys after extensive use. As it gets hot, creosote emits a foul, stale burnt wood smell that is forced back into the house by down drafts. Creosote is usually removed by routine chimney cleaning, though it can become stuck in flue joints and cause odors to remain. Creosote is also the main cause of chimney fires. Installing a sealing damper on the top of a chimney can prevent down drafts.

Dead Animals

Some foul odors in chimneys are caused by dead birds and animals. This type of odor is usually caused when a bird, raccoon, squirrel or other creature breaches the chimney cap and falls or climbs down into the chimney. When they are unable to get out they die and decompose. You can reach in and remove the dead animals, but a professional is usually required.

Animal and Bird Defecation

While some birds and animals will die inside chimneys, others safely use them for shelter. Birds, such as swifts, will nest if given the chance. Feces from baby birds accumulate inside chimneys. Raccoon and squirrel feces will also cause foul odors that can only be removed by clearing the area of animals, cleaning the chimney and installing a cap with a strong screen.

References

• University of Missouri Extension; Cleaning Stovepipes and Chimneys; David Barker; 1993
• Chimneycleaners.com: Frequently Asked Questions