Why Does Smoke Puff out of a Wood Stove & a Stove Pipe?

Weather Factors

• If you vent your stove through an outside masonry chimney and if it operates well most of the time but back-puffs on rainy days, the problem is that the wet bricks, concrete or stone pull the heat away from the emissions. This reduces the draft, or the force of the air moving up the chimney. Rain can also get into a chimney built in the center of a room and any heat generated by the stove is absorbed by the water, creating an inefficient draft. Installing a cap on it will deflect the rain away from the chimney opening and keep the flue liner dry. You can also apply a repellent to the outside of an exterior chimney that prevents water from soaking through the masonry. If it's warmer outside than inside, you may need to prewarm the flue by holding a piece of lighted paper inside the stove and keeping a strong flame burning until the smoke moves in the direction it should.

Chimney Obstructions

• Smoke can puff out of a stove or between the sections of stovepipe if the chimney is obstructed by any type of debris, including leaves or twigs, particularly during the fall months. An open chimney is also appealing to all types of animals, including birds, squirrels, snakes, raccoons, chickens, and bats. Not only do these creatures take up residence in chimneys, but they can also foul things up with their droppings. Prefabricated chimney kits normally include a cap and screen cage that fit over the top of the flue. You can install similar devices on a masonry chimney, as something as simple as a bird's nest can block the flue and even result in a chimney fire. Minimizing backpuffing is another reason to have your chimney cleaned regularly

Exterior Factors

• Objects such as nearby trees, the exterior walls of nearby buildings, or roofs can block the flow of air between buildings. One solution is adding height to your chimney or installing a chimney cap that better regulates the flow of air in and around it. To be effective, you must increase the chimney's height so that it is at least two feet higher than any obstacles that are within 10 feet of it on all sides.

Interior Factors

• To provide the ideal draft, the top of any chimney must extend at least three feet above the highest point of the roof it projects through or is attached to. Where the wood stove is located in the building also affects the draft and can produce smoke puffing from it. Draft depends on interior versus exterior air pressure, and the lower a stove is located in a building, the harder the warm air must work and the further it has to travel to exit the flue. The cure can sometimes be as simple as opening an exterior door or window while getting the stove going, or it may require the installation of an air intake duct connected to the stove's main air inlet, which is normally located slightly below the firebox.