It is good to know what hidden dangers may be lurking in your chimney in order to keep you and your home safe from fire and/or carbon monoxide poisoning. This includes inspecting flue tiles for gaps, cracks, and flaking in addition to other concerns.
Gaps Between Flue Tiles – A chimney’s purpose is to safely vent hazardous flue gases (from the combustion process) from your home. These gases can contain creosote/soot, carbon monoxide and corrosive chemicals. Flue tiles are typically sealed with mortar to keep these gases within the flue. But over time, the mixture of heat, moisture and chemicals will erode the mortar, leaving gaps or voids between flue tiles.
Cracked Flue Tiles – Flue tiles can crack due to “sudden occurrences” such as a previous chimney fire, lightning strike, or seismic event. Cracks may also be caused by poor workmanship or the ongoing settling of your home.
Flaking Flue Tiles (Spalling) – Years of exposure to corrosive chemicals and moisture from combustion can attack clay flue tiles, causing pieces of the flue liner to flake off or delaminate, a process known as spalling.
Types of Chimneys and Fire Possibilities
Chimneys can be made from various materials. Two of the most common types of chimneys are masonry chimneys and metal chimneys. Fires that occur in masonry-built chimneys can cause the chimney liner to break and crack (if there is a chimney liner), can crack tiles, and can also be so hot as to melt the mortar that holds the chimney together.
Chimneys crafted from metal are frequently found in homes throughout the United States. Although created to hold up to very high temperatures, metal chimneys can still be damaged by fire. Should this happen, the chimney liner and/or chimney must be removed and replaced with a new one.
Reducing the Possibility of a Chimney Fire
It is critically important that you keep your chimney clean. Build-up of such substances as creosote can be very hazardous. Creosote is a black or brown substance that may appear gooey, flaky, or crusty. It almost looks like tar. It is important to keep your chimney clear of creosote because it can catch fire.
Creosote and the build-up of other hazardous substances can be the result of not enough air supply in the chimney. How does this happen? Air supply reduction occurs when you close glass fireplace doors, not opening up the flue enough to let air flow, and just not enough air flowing through the chimney. In addition, using unseasoned wood in your fireplace can contribute to creosote build-up. Unseasoned wood has moisture in it taking it longer to burn. Unseasoned wood that burns at a lower temperature for a longer period of time can create the perfect condition for creosote to build-up within the chimney.
Signs of a Chimney Fire
According to the Chimney Safety Institute of America, there are several specific signs that you can look for to determine if there has been a significant fire in a chimney:
- A rain cap that is discolored or misshapen.
- Cracks in the masonry on the outside of the chimney.
- Evidence of creosote in the chimney itself. The creosote may look like a honeycomb and may be puffy looking.
- The roof surrounding the chimney is damaged/melted.
- Flue and other tiles that are cracked or missing.
Enjoying a fire in a fireplace is one of the joys of home ownership. However, enjoying a fire in a fireplace does come with some dangers. To reduce the possibility of a chimney fire, have your chimney cleaned and inspected at least once a year. If items are found that need to be fixed and/or replaced, make sure to have these issues corrected before your use your fireplace again. In this way, you and your family can enjoy your fireplace safely.