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Winter Chimney Odor Issues

While burning wood in the fireplace on a chilly day, you are probably expecting to relax to the warm, soothing, and pleasant aroma of oak, chestnut, pine, or other favorite wood. Instead, a strange and unpleasant odor fills the room that worsens as the wood continues to burn and you’re wondering where it’s coming from. Winter chimney odors are often a warning sign of a potential chimney problem such as a flue obstruction, excessive creosote, or a water leak. Let’s explore a few possible causes and fixes to those winter chimney odor issues.

chimney debris, bordentown njAnimal Nests

The chimney is a popular hideout for small animals looking for a place to rest while escaping predators. However, many of these critters, like squirrels, raccoons, and even little birds, find that they can’t get out as easily as they climbed in and perish inside the flue.  The decaying organic matter will cause a strong foul odor, especially when exposed to heat. You may also hear gnawing, clawing, or scratching noises in the chimney, indicating that there may be live animals stuck in the flue.  Don’t smoke them out. Instead, contact a trained chimney technician or Mercer County Chimney Services who will safely and humanely remove any wildlife that has taken refuge in your chimney. Installing a chimney cap with a mesh screen is a simple solution that will help keep animals and pests out of the chimney.


Creosote is one of several by-products that are produced during the combustion of wood in the fireplace. It is mostly carbon and tar that sticks to the interior masonry walls and other components as smoke and exhaust exit the chimney. Without regular chimney sweeping, creosote will harden into a thick, crusty, charcoal-like substance known as stage 3 creosote. An excessive accumulation may cause the chimney to smell like burning tar or a smokey barbecue when you light the fireplace in the winter. Since stage 3 creosote is highly flammable, you should avoid using the fireplace and immediately schedule a professional chimney sweep to remove the creosote.

Negative Air Pressure

Negative air pressure is a common problem, especially in newer, more energy-efficient homes. The tight building envelopes in energy-efficient homes restrict airflow that can impede the chimney draft resulting in negative air pressure. Ceiling and exhaust fans, the clothes dryer, and other appliances that require ventilation are competing for oxygen that can cause a sudden change in air pressure. When negative pressure occurs, the chimney draft reverses, and a downdraft forces smoke, soot, and debris out the fireplace instead of the chimney. The air movement stirs up the odors releasing a bad smell in the living space. Opening the window slightly will allow sufficient oxygen to correct the negative air pressure. Consult with your chimney technician for a more permanent solution, such as a top-sealing damper.

leaky chimney, Ewing NJWater Leaks

Water can leak in the chimney through various entry points, including a broken or missing chimney cap, damaged flashing, gaps in the mortar joints, and other masonry damage. The humidity can also cause condensation to occur on the interior masonry and chimney liner. Water leaks mix with the soot, ash, and other debris that can release a foul odor. It can also promote mold, mildew, and other bacteria resulting in an earthy or musty smell. Since water leaks can cause severe damage to the masonry, chimney liner, and other components, it is vital to schedule a chimney inspection as soon as possible to uncover the source of the water leak.

If foul odors are coming from your chimney or fireplace, schedule an appointment with a professional chimney sweep or Mercer County Chimney Services. They will resolve the issue causing the odor, making your fireplace experience enjoyable.