Chimney Fires

A chimney fire is a preventable event that has the potential to cause damage to your chimney or even a house fire.  Chimney fire prevention is one of the reasons to have your chimney swept and inspected on a regular basis.  We will be discussing the cause and effect of a chimney fire, how to prevent them, and what to do during and after should one occur in your chimney.

There are a few myths surrounding chimney fires that we would like to address.
     We have heard many stories of "burning out the creosote," essentially causing a chimney fire deliberately to clean out the chimney.  This practice has the potential to cause the same damage as a "naturally" occurring chimney fire and is to be avoided.  Creosote that has pyrolysed as a result of a chimney fire can expand substantially and actually block more of the chimney than the buildup you started with!
     We have seen a trend that people don't consider chimney fires that dangerous and don't don't take proper steps to mitigate possible damage or have the chimney inspected after the chimney fire and continue to use the chimney.  It is not uncommon for a chimney fire to cause clay flue tiles to crack and can stress or even buckle the metal in factory built chimneys.  This damage is usually not evident to the homeowner without an inspection.  Heat from the chimney fire can be conducted to combustible building materials next to the chimney or hot brands flying out of the chimney can land on the roof and cause a house fire (and in the example of flying brands, it might not even be your house that catches fire!).  If you suspect a chimney fire close off as much air to the chimney as possible and call the fire department.  Afterwards have the chimney inspected before further use.
     When presented with evidence that a chimney fire has occurred, sometimes we hear "I couldn't have had a chimney fire, I don't burn wood!"  While wood is the most common fuel in use that could lead to a chimney fire just about any fuel has the potential to produce flammable products of combustion that could build up in a venting system.  Yes, this even includes gas!  While extremely rare, chimney fires from other fuels can be just as damaging.  Have those chimneys checked out no matter what fuel you use!

A chimney fire occurs when deposits of creosote and other flammable material in the chimney is ignited and burns within the chimney structure.  Please see our other page, "Creosote - What is it and Why is it Bad?", for more information on how and why creosote appears in chimneys.  The fact that flammable material must be present for a chimney fire to occur brings us to our most important point: Chimney fires are completely preventable!  A clean chimney without buildup cannot have a fire.  You can prevent dangerous buildup in your chimney in several ways:

1. Burn proper fuel for your appliance with any necessary adjustments to fuel delivery or airflow properly made.  This means dry and properly seasoned cord wood, proper adjustments to an oil fired heater, etc.  This will help reduce or prevent the creation of flammable material that may collect in your chimney.

2. Avoid low temperature burns over extended periods.  Even with proper fuel, dampering a fire down to much can cause incomplete combustion and cooler flue temperatures, both of which contribute to buildup in your chimney.

3. Have your chimney swept and inspected regularly.  This will allow you to know about and correct issues with your chimney as well as clear any buildup that may be present.  Clean chimneys don't have chimney fires!

While we have discussed why chimney fires occur and how to prevent them, we know that not everyone will heed these warnings so lets go over what to do in the event of a chimney fire.
     The first step is to recognize what is going on.  Often chimney fires are very noticeable and there is very little doubt about what is happening.  These "free burning" chimney fires will draw enormous amounts of air into the chimney causing a loud rushing or rumbling sound.  Chimney connector pipe may vibrate or rattle.  You may hear crackling and popping noises from within the chimney.  Outside you will see a large volume of smoke exiting the chimney possibly along with embers and flaming brands.  There is also a slow burning version of chimney fire that may not be noticeable at all but can be just as dangerous.  You may still hear crackling or popping but the spectacular pyrotechnic display of a free burning chimney fire may be absent.  While the fire burns much slower, it can burn just as hot as a free burning chimney fire and thus cause the same damage.
     As soon as you suspect a chimney fire, try to prevent as much air from entering the chimney as possible.  Close fireplace doors, close down stove air controls, block off any open unused thimbles, etc.  Oxygen is essential to a chimney fire and the less it can get the less severe the fire could be.
     Call the fire department.  Nobody wants all the attention from the neighborhood a fire engine in front of your house can create but chimney fires have the potential to spread to the house and should be extinguished as quickly as possible.  While waiting for the fire department, use a garden hose to keep your roof wet in an attempt to keep any flaming material from igniting it.
    Call a chimney professional.  After the fire is out and the fire engines are gone, there is still a danger.  It comes when a homeowner attempts to use the chimney after a chimney fire without it being checked out.  Damage from the chimney fire can make your chimney unsafe to use and could lead to several dangerous situations including carbon monoxide buildup in your home, or even a house fire.  Never resume using a chimney after a chimney fire without a chimney professional conducting a thorough inspection, even if a firefighter says it's ok.

To wrap it up, let's remember three things.  First, chimney fires are a dangerous event and not to be taken lightly.  Second, never use a chimney after a chimney fire until a chimney professional has inspected it.  And last and most important: chimney fires are completely preventable!  Using your heating appliance properly with proper fuel and having your chimney inspected regularly will help you to enjoy years of safe heat.