Chimney fires are a frightening prospect for any homeowner who burns with wood (or pellet).  Beyond damaging your chimney, chimney fires can spread to your home causing injury and death as well as extensive property damage.  But chimney fires can be eliminated with proper precautions.

Understanding Chimney Fires

There are two types of chimney fires, free burning and slow burning.  Free burning fires are easier to detect because you will hear a loud roar like a freight train is running through your living room.  Billows of smoke and spewing flames will pour out of your chimney.  Slow burning fires are silently destructive.  They burn quietly at high temperatures for a long period of time.  While slow burning fires appear less dangerous, the high temperatures can cause serious damage to your chimney and catch other parts of your home on fire.

Both types can cause extensive damage even if contained to your chimney.  Chimney fires can reach 2000 degrees Fahrenheit, which is hot enough to melt some metals.  This is why even prefabricated chimneys, that are designed to withstand high temperatures, are still liable to be damaged by a chimney fire.  Often, the high temperatures will distort or collapse the metal liner.  If you have a masonry chimney, a chimney fire may cause structural damage by cracking mortar, bricks and stone or causing a chimney liner to break or collapse.  The damage caused to a chimney by the flame is what puts the rest of your home at risk because it creates pathways to other flammable materials like the walls and roof of your home.

How to Respond to a Chimney Fire

If you do have a chimney fire, your immediate response should be to get everyone out of your home.  Once you’re all safe, call the fire department.  While you’re waiting for them to arrive, you can help prevent the fire from spreading by dousing your roof with a garden hose.

It’s important to bring in a professional chimney sweep in after a chimney fire to determine the original cause of the fire and assess the damage.  You may need to have your chimney repaired or the liner replaced before your fireplace is safe to use again. If the damage is not repaired a second chimney fire could bring down your home.

What Causes Chimney Fires

The leading cause of chimney fires is creosote buildup.  Creosote is a highly flammable substance that is a byproduct of incomplete combustion.  It’s created when volatile gasses and particles in smoke from an inefficient fire meet cooler air in your chimney and form a tar-like condensation along the walls of your chimney.  Eventually if you don’t have your chimney cleaned (or aren’t burning properly) it can be plugged by creosote.

The more creosote in a chimney the more likely it is to catch fire.  If the level of oxygen and the temperature within your chimney are at the right level, it can cause the creosote buildup to ignite. When the level of creosote in a chimney is low, there is little danger. In that instance, the fire would burn out quickly. When there are large amounts of creosote, it can burn for a long time and will cause the greatest amount of damage if ignited.

Preventing Chimney Fires

Most chimney fires can be prevented by reducing the buildup of creosote in your chimney and having your chimney annually cleaned out and inspected by a chimney sweep.

To reduce the accumulation of creosote, follow these practices:

  • Only burn seasoned firewood: green wood requires more energy to burn because of the higher level of moisture which results in a less efficient fire and smoke that is higher in particulates and volatile gas that will form into creosote. Seasoned wood burns hotter and more efficiently creating less creosote. To ensure that your wood is properly seasoned, test it with a moisture meter (visually, it’s impossible to tell if the inside of wood is dry).
  • Only use dry newspaper or proper kindling to start a fire.  Gasoline, kerosene and other composite products should never be used to start a fire in your fireplace.
  • Only use unadulterated firewood: You should not burn stained, glued or painted wood, cardboard, wrapping paper, or trash because they contain volatile organic compounds and toxins. These substances are not only harmful for the environment (and humans), they also contribute to creosote buildup.
  • Burn your stove or fireplace properly: Different appliances require different burning techniques.  Refer to your manual for specific operating instructions for your appliance.

Remember that reducing the amount of creosote that builds up each burning season is only the first step to chimney fire prevention.  The second step is bringing in a professional chimney sweep, at the end of the season, to clean out the creosote that has accumulated and inspect your chimney.  A clean chimney means a safer home.  Adding this year’s creosote on top of last years can lead to a dangerous collection that puts your home more at risk.  By taking both steps you can enjoy your fireplace without worrying.