What is a Flue or Chimney Fire and Am I at Risk?
A chimney fire or flue fire can occur as a result of creosote or soot within the chimney lining catching fire. One of the primary reasons to have an annual chimney inspection is to determine whether creosote has built up to the point of making a chimney fire a real threat. The National Fireplace Institute (NFI) recommends having a chimney cleaned once a minimum of 1/8” of soot or creosote has accumulated. Anytime a chimney is not maintained as recommended, the household may be at an increased risk of a chimney fire. Many people don’t realize when they’ve had a chimney fire, which can be extremely hazardous. The reality is that creosote is deposited in the chimney flue anytime there’s a wood-burning fire. There are ways to minimize the amount of creosote in your chimney and therefore reduce the risk of a flue fire.
Three Stages of Creosote
Since creosote is the major culprit in setting the stage for a chimney fire, it’s helpful to understand that creosote has three forms. In the first form, creosote is dusty or flaky and easy to remove. In the second form, it is tar-like or crunchy and more difficult to remove. In its third and most hazardous form, creosote is glazed and gummy or glass-like and hard – it appears as though tar has been poured down the chimney. This type of creosote is very difficult and can be impossible to remove. The third form is especially hazardous in the event of a chimney fire because the fire persists longer, creating dangerously intense temperatures.
Signs of a Chimney Fire
Homeowners don’t always recognize that they’ve had a chimney fire. While the fire in the flue is happening, there are two primary ways people realize what’s going on. The first is a roaring sound coming from the chimney, and it sounds almost like a train. The second is that sparks and flames may shoot out of the top of the chimney. For anyone who isn’t certain they’ve had a chimney fire or is perhaps completely unaware that one has occurred, the following provides evidence of a chimney fire that chimney professionals can easily identify:
· The creosote has become honeycomb-like or puffy.
· Flue tiles are cracked or collapsed, and large bits of tile may be missing.
· The chimney cap may be distorted or discolored.
· The television antenna attached to the chimney has heat damage.
· There are cracks in the exterior masonry.
· There is evidence that smoke has escaped through mortar joints of the chimney masonry or through tile liners.
· The metal damper or other metal internal components of the chimney, such as a metal smoke chamber, may be warped.
Tips for Reducing Excessive Creosote Buildup in the Flue
If a flue is too large for the appliance it is connected to, the result can be excessive creosote. When the draft in the flue is sluggish, gases expand, filling the space, and then quickly cool, which causes creosote to stick to the chimney walls like glue. The solution is to ensure proper installation of a wood-burning appliance, complete with a flue of the correct size. The following are other causes of excessive creosote deposits:
· Certain wood-burning habits create an environment which causes creosote to form more quickly. For example, smoldering fires that don’t get hot enough to burn gases lead to more creosote. Burn smaller, more efficient fires, making sure fires get plenty of air. In addition, make sure there is a strong draft in the chimney by removing obstructions.
· Never burn green wood because the heat from the fire burns out the moisture before getting around to providing heat. Fires with green wood create excessive creosote. Burn seasoned wood only.
· When a chimney flue is neglected, creosote is able to build up, season after season. Eventually, a flue fire becomes a huge risk. Annual chimney inspections plus chimney cleaning helps to prevent hazardous chimney fires.
Thousands of chimney fires occur in the U.S. every year, and many are deadly. The terrible reality is that a chimney fire can lead to a house fire so intense that occupants of a home are oftentimes unable to escape to safety. Once a chimney fire has occurred, it is imperative that the fireplace or wood stove not be used again until the flue lining has been inspected. In most cases, a flue liner replacement is necessary, following a chimney fire. Other masonry repairs and additional equipment repairs may also be required.
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