As a retired firefighter and a CSIA Master certified chimney sweep, I care a lot about fire safety and have dedicated decades of my life to reducing chimney fires and house fires in this community. I also know that in many ways, education is the key to fire prevention. So let’s get some of those common questions about chimney fires answered!
What causes chimney fires?

what to know about chimney fires - crofton md -clean sweep aa (1)The #1 cause of chimney fires is improper maintenance and neglected sweepings of the chimney system.

The National Fire Protection Association (NFPA) and the Chimney Safety Institute of America (CSIA) state that all chimney and venting systems should be inspected yearly and swept as needed. But many homeowners think, what’s the big deal about a dirty chimney?

Well, here’s how a dirty, neglected chimney can lead to a chimney fire…

Flue liners aren’t just generic sizes that you can choose based on what you want. Each liner is sized using a mathematical equation based on the size of the firebox, be it a wood stove or a fireplace. In other words, the size of the firebox in the appliance determines the size of the exhaust pipe needed.

Now, let’s say you neglect to sweep your chimney and you’ve got heavy creosote or baked-on creosote (tar deposits) coating the inside of that liner…what’s it doing? It’s reducing or shrinking the size of the liner’s opening.

Can’t be too big of a problem, can it?

Well, imagine that you have an 8-inch pipe coming off of your appliance and you have an inch of creosote or soot on the inside of that liner. That creosote and soot would reduce the liner’s opening by an inch on each side.

So now you’ve gone from having a liner that can vent about 50 square inches when perfectly new and clean to something that drops down to about 28 square inches. You’ve almost cut the exhaust rate of flue gases in half!

When this happens, you start getting smoke coming back into the home, and because you now have superheated gases funneling through a smaller area, those gases cause the tar (creosote) in the liner to bubble, ooze, and emit vapor. That vapor then ignites and causes a chimney fire.

The #2 cause of chimney fire is improper use.

Truth is, you could have a chimney that’s in reasonably good shape with very minor sooting and deposits, and still have a chimney fire. How?

Well, let’s say it’s Christmas time and you figure there’s no harm in overloading the firebox for a big festive fire and tossing in some styrofoam, cardboard, or Christmas wrapping paper.

These materials actually produce a lot of heat, very quickly, and can essentially create a fireball in your flue. An otherwise “safe” chimney now has a chimney fire because of improper use. Anything that can ignite will, and within 30-90 seconds, your liner will crack (if it’s terra cotta) or your pipe will separate (if your liner is metal). If it’s not stopped, that chimney fire can spread to other areas of your home.

What should you do if you have a chimney fire?

When you have a chimney fire, the very first thing you need to do is dial 911. Depending on where you live, it’s going to take anywhere from three to maybe even 10 minutes or more for the first fire truck to arrive. This can be very scary for a homeowner.

Think about how long 30 or 60 seconds feel when you’re holding your breath underwater. Now, imagine how long two, three, four, five minutes will feel when you have a fire going on in your home and you’re waiting for somebody to come help.

So act quickly, get out of the house, and call 911.

Once the fire department comes and they’ve mitigated the emergency, the next phone call should be to a CSIA certified chimney technician to come out and do the proper level 2 inspection on the system to make sure it’s still suitable for use.

What that means is that they will have a camera that goes through the system, checking for any damage done by either the chimney fire or by the extinguishing methods that the fire department might have used to put out the fire.

If the fire department sprayed water in there, the water could have caused the metal or terra cotta liner to crack or warp. If that happened, the inside liner will need to be repaired or replaced before you can use the system again. The only way you’re going to know that is if you have a proper level 2 inspection performed, which is what is required by national fire code.

What are some misconceptions about chimney fires?

The problem with chimney fires is people don’t understand how fast everything happens. What can happen in two or three minutes is life changing…

You can have a fire start in the chimney, crack the liner in less than a minute or two, go into the wall space, set the wall on fire, travel up into and walk across your attic, and then be blowing through your roof before you’ve even processed what’s happening.

I’ve seen that many times.

Aside from how rapidly chimney fires can spread, another thing that makes them so dangerous is that you may not even know a fire is raging in your chimney, even if you’re in the same room as the fireplace or stove…

In fact, the most common chimney fire is a slow-burning chimney fire that the homeowner isn’t even aware of. The stereotypical chimney fire sounds that people talk about when they say it sounds like a plane’s landing in their dining room or a train’s coming through their living room, is really air.

That “whoosh” is the fire burning with such ferocity that it’s sucking the air out of the home. That’s where you’re getting the jet engine sound. But not all chimney fires are accompanied by loud sounds.

Every year, at least once or twice, as a fire firefighter we’d get called to a chimney fire and we’d rush up to the door, knock on it, and try to open it up. And the homeowner would be looking at us thinking, “What are you doing here?” He was watching football in the same room where the wood stove or fireplace was and had no idea that he had what looks like a roman candle shooting up out of the top of his chimney.

How many chimney fires occur in the U.S. every year?

From 2012-2016, fire departments responded to more than 52,000 fires involving heating equipment. While we have made some headway in terms of reducing chimney fires — partially because people are burning less wood less frequently compared to what they were doing in the 70s, 80s, and early 90s and partially because systems have become more efficient — chimney fires are still pretty common.

Is there a fuel type that is more susceptible to chimney fires?

Most chimney fires involve wood-burning appliances such as wood stoves and fireplaces because of the tar (creosote) that wood produces and its flammability.

What can you do to reduce your risk of a chimney fire?

There are a couple of things you can do to reduce your chance of having a chimney fire, and they’re pretty simple!

  • Burn dry, well-seasoned wood. Any kind of wood is good (hardwood or soft) as long as it’s well seasoned, dry, and has a moisture content of 25% or less.
  • You can purchase a moisture meter at your local home improvement or hardware store.
  • At a minimum, have the chimney inspected on a yearly basis and swept if needed.

Final tips on enjoying your wood-burning fireplace safely:

  • Never use chemical fire starters.
  • To get the fire going, the best thing to do is to get some dry kindling and a small amount of newspaper.
  • Make sure your damper is open before you light the fire so that smoke can be properly ventilated.
  • Make sure you’ve got a good draft by preheating the inside of the flue if you can.
  • Invest in fire extinguishers for your home. ABC fire extinguishers are good combination fire extinguishers that’ll work for most common fires you might experience in your home.

A good way to preheat the inside of the flue is to hold an electric hairdryer up and point it towards the damper. Or you could wind up a couple of pieces of newspaper on an angle so it looks like a large ice cream cone, and light the end where the scoop of ice cream would go.
Hold it up towards the damper, and as it starts to get warm on your hand, then you should be able to take that piece and light the fire.

Either method of preheating the flue will start to prime the damper and flue with warmer air to create a draft. Then, when you do actually light the fire, you will already have the air currents moving in the right direction.

You see, cold air is much denser and heavier than hot air, so if you have a flue liner that’s 1-foot square and 20 ft. tall, you have 20 cubic feet of air. That means you’re going to need 40-50 cubic feet of hot air to push that cold air out and get the smoke going in the right direction.

As far as fire extinguishers are concerned, you should have one in the kitchen, one in the garage, one in the basement (if you have a basement), and maybe one in a hall closet.

Don’t just put them in rooms where fires are likely to happen, because if you have a fire in the kitchen, you don’t want to have to go into the kitchen to get the fire extinguisher. Likewise, having a fire extinguisher next to your fireplace won’t be much help if the fire is in the fireplace. Instead, consider having one in an adjacent room so you only have to go near the fireplace once, armed with a fire extinguisher in hand.

A fireplace, stove, insert, or log set can be a great thing to have — just make sure you’re taking care of your heating appliance, getting it the proper maintenance it needs every year, and practicing safe use all winter long! If you have any questions you’d like us to answer, feel free to reach out. We’re happy to help!