How Bad Is a Chimney Fire and Why Is a Chimney Fire Dangerous?

So, what makes a chimney fire so dangerous and how bad is it? Chimney fires are dangerous because they can rapidly spread to other areas of the home, putting those within the home at risk of injury or death. Not only that, but they can cause a lot of damage to the chimney itself.

Here’s a snapshot of the kinds of damage chimney fires can cause to your chimney, depending on which type you have:

• Masonry Chimneys – When a chimney fire occurs in a masonry chimney – whether the flue is an older, unlined type or tile lined to meet current safety codes – the high temperatures at which the fire burns (around 2000 degrees F) can melt mortar, crack tiles, cause liners to collapse, and damage the outer masonry material. Most often, thermal shock occurs, tiles crack, and mortar is displaced. All this damage provides a pathway for flames to reach the combustible wood framing of the home, which is extremely dangerous.
• Prefabricated/Factory-Built Metal Chimneys – In most jurisdictions in the U.S., metal factory-built chimneys that are designed to vent wood-burning stoves or prefab metal fireplaces must pass special tests or they can’t be installed. Most tests require the chimney to withstand flue temperatures up to 2100 degrees F, without sustaining damage. Even still, if there’s a chimney fire, these systems can be damaged. And unfortunately, when prefabricated, factory-built chimneys are damaged by a chimney fire, they must be replaced.
• Wood Stoves – Wood Stoves are made to contain hot fires. The connector pipes that run from stove to chimney, however, aren’t. They can’t withstand the high temperatures produced during a chimney fire and will warp, buckle, or even separate from the appliance and chimney because of the vibrations of air turbulence during a chimney fire. If a separation does occur, fire, heat, and smoke can transfer to other areas of the home. Additionally, like prefab chimneys, if the connector pipes on a wood stove are damaged, they must be replaced.

Another consideration is what a chimney fire can do to the home if it spreads. A rapidly spreading fire can cause extensive damage to walls, ceilings, attics, framing, and furniture. All those repair and replacement costs can add up quickly.

When you consider that a chimney sweeping and inspection cost around $150-450 and could potentially save you thousands or even tens of thousands of dollars in repairs, the smart choice is obvious: schedule routine inspections and cleanings for your chimney system.

Where Do Most Chimney Fires Start?

Most chimney fires start inside the flue where there’s either creosote buildup or a flue blockage of some kind. As heat from the fire reaches these flammable materials, the creosote or blockage ignites, starting a chimney fire.