Chimney fires are the direct result of burning a fire in a chimney that has not been regularly inspected and swept clear of creosote. These fires can be large and dramatic, with loud cracking noises and lots of dense smoke, but can also burn slowly if they don’t get enough air for fuel. These slow burning fires reach very high temperatures that cause as much damage to the chimney structure and combustible parts of the house as the louder and more dramatic fires do.
So what causes the chimney fire? The purpose of the chimney is to expel the by-products of the wood that is burning to create heat. This includes smoke, vapors, gases, unburned wood particles, assorted minerals, among other things. As these hot particles rise in the cooler chimney, condensation occurs. This creates the sticky residue known as creosote.
The longer the smoke is in the flue, the more likely it is that creosote will form. Failing to open the damper wide enough to provide adequate air flow, burning unseasoned wood, and cooler than normal chimney temperatures all lead to quicker build-up. This means if we have a particularly cold winter, and you burn a fire often, you may need to have your chimney swept more than once a year.
When a fire does occur in a masonry chimney, it typically melts mortar, cracks tiles, causes the liner to collapse and damages the outer masonry of the chimney. Once the tiles crack and mortar is displaced, the flames can reach the wood frame of the house, which is extremely dangerous and typically causes the loss of a home.
Metal chimneys today are designed to withstand flue temperatures up to 2100 degrees without sustaining damage. These are required installation in new builds in many states in the U.S. While a fire is less likely, it could still happen and if it does, the factory-built metal chimney cannot be repaired, and must be replaced.
Wood stoves are designed to contain hot fires. But the connector pipes that run from the stove to the chimney typically cannot withstand the high temperature that a chimney fire creates. If a chimney fire occurs with a wood stove, the connectors can warp, buckle and separate. These cannot be repaired and must also be replaced.
Call Chim Chimney today and have your chimney inspected and swept so you are ready for a cozy season of warm, crackling fires this winter.