Chimney Fires, Prevention and Response

With the colder weather, we've started responding to flue fires.  We thought it might be a good time to put some information out regarding this type of fire: what they are, what you should do if you have one, and why they can be especially dangerous.

If you have a wood burning stove or fireplace you may already know about inspections, cleaning, and the general care and maintenance of your chimney flue. If you don’t, there’s a lot of good information on the web you can use to evaluate what condition yours may be in, and what your fire risk may be.  Or you could hire a professional to inspect and service your system.

A chimney fire is the uncontrolled burning of creosote ( a highly combustible black or brown substance) on the inner surfaces of chimney tiles, flue liners, stove pipes, etc. Creosote buildup can occur if the fireplace or wood burning stove has a restricted air supply, is burning unseasoned wood, and has cooler-than-normal chimney temperatures. This creosote buildup can ignite if the fire is hot enough or if burning embers attach themselves to the creosote.

Chimney fires have the potential to burn explosively. They can be noisy and dramatic enough to be seen and heard by neighbors or people passing by. The flames and dense smoke they produce can shoot out of the top of the chimney. With this type of fire people report hearing a low, rumbling sound like a freight train or a low flying airplane. Under certain situations, slow-burning chimney fires can also occur. These fires don’t get enough oxygen or have enough fuel to be as dramatic or visible, but they can reach very high temperatures and can cause as much damage to the chimney structure and nearby combustible parts of the house as a visible fire.

If you have a chimney fire, it’s important to get everyone out of the house, including yourself, as soon as possible and call 911. If the fire is confined to the chimney flue and there’s no smoke present in the house, there are a few things you can do that may help to mitigate the problem and potentially save damage to your home. Remember, a home is replaceable; a life is not. If you don’t know the extent of the fire, stay out. Otherwise, these steps can be attempted:

• 1. Close the chimney flue and all other dampers to limit the amount of oxygen available to the fire

  2. If available, use a chimney fire extinguisher such as the "Chimfex", available at Home Hardware

  3. Remove the fuel (wood) from the fire box.  If it can be done safely!

  4. Close all other exterior doors, windows and interior rooms in the house to limit the potential for spread if the fire escapes the chimney

After the fire has been extinguished, do not use the fire place until it has been properly inspected and repairs are made by a qualified service technician prior to use. Chimney fire damage and repair may be covered by homeowner insurance policies, but you may want to check with your insurance provider to verify the coverage you have.

This type of fire can get out of the chimney and into the combustible areas of your house, usually in places you can’t see or get to easily.

The reason this happens is because a chimney fire can cause a weakening of the mortar joints in a masonry chimney, or in the slip joints of a manufactured flue,  allowing the hot gases and embers from the chimney fire to vent into the spaces between floor levels, ceilings, and attics of your home’s structure.  You might think that the fire is out, but in fact it’s slowly smoldering somewhere you can’t detect it. Hours may pass before you’re aware that something in your house is on fire.  By the time you do realize it, it may be too late.

This is why we send a full response to chimney fires. Having multiple fire personnel and equipment showing up to your chimney fire may look like overkill for something that’s usually handled by one or two guys on a ladder, but because you can’t know the extent of the problem without careful investigation, it’s better to have more resources available just in case.

Bottom line is to keep your wood burning appliances in top shape, have your chimney cleaned regularly, and have a plan in case you have a problem.  Be aware and be prepared