What Types of Creosote Are in My Chimney?

By official classification, there are three types of creosote. If you run a wood-burning heating appliance, you should be familiar with all three types, how they are formed, how they can be removed and the dangers they can present.

Any time wood burns, creosote is produced. It’s a flammable byproduct of smoke that remains in the flue and attaches to the liner or chimney masonry. While you can’t completely prevent creosote from forming in your chimney, you can significantly reduce the amount that forms by remembering this formula:

Dry wood + hot flue + plenty of air

Stage I creosote

This creosote is primarily soot and is relatively easy to brush out of the flue. Stage I creosote forms when the burning wood is dry and combusts thoroughly and there is plenty of air to keep the fire hot and draft the smoke efficiently up into and out of a warm flue.

Stage II creosote

When air is restricted in the firebox, conditions are perfect for making stage II creosote, a black, flakey substance with hardened tar that is challenging to simply brush away. Less draft air means lower-temperature burns, more smoke and a more sluggish path for smoke through a cooler upper flue. Obstructions within the flue, an air-tight house and glass fireplace doors all can contribute to hampered air flow.

Stage III creosote

Stage III creosote is the most dangerous. It is a hard, concentrated fuel that may partially burn off with a small chimney fire, but rarely goes away completely. In fact, in most cases, this type of creosote keeps building up until you may end up with 100 pounds or more of the substance in your chimney. This sets the perfect stage for a disastrous chimney fire.

Stage III creosote forms when:

· only some of the wood actually burns

· a huge amount of smoke is generated

· the upper flue is very cold

· very little air gets to the fire to aid combustion

· the flue is too big for the appliance (fireplace, stove) connected to it

The circumstances that cause stage III creosote are similar to those that cause stage II, only in stage III they’re more pronounced.

Creosote removal

As noted, stage I creosote usually can be brushed away. Stage II usually requires a tool called a rotary loop that has metal rods that circulate rapidly and break the creosote away from the liner or the masonry. Removing stage III creosote is very difficult and likely will involve steel chains instead of rods on a loop device along with special chemicals that eat away at the buildup.

Removing any of the creosote stages should be performed only by a trained, CSIA-certified chimney technician.

Reducing creosote buildup

The formula we mentioned earlier, dry wood + warm flue + plenty of air, is the best way for you to keep creosote buildup at a minimum. But there’s a fourth part of the formula that’s just as important: annual cleaning by a certified, professional chimney sweep. Use this full formula, and you’ll be able to enjoy your beautiful fireplace with perfect peace of mind year after year.

Chimney Saver Solutions of Richmond, VA, does just what our name implies: we save your chimney with expert chimney cleaning, chimney inspection and chimney repair. Call us at (804) 440-5000 for the very best in workmanship and service for your fireplace, chimney, heating stove or furnace.