Fireplaces are designed to safely contain a wood-fueled fire, while, at the same time, heating your home. Chimneys are designed to expel the substances—smoke, water vapor, gases, etc.—produced from your wood fire. As these substances are ushered up and out of your house, another substance is formed in the process; that substance is known as creosote.
You’re probably asking yourself, “what exactly is creosote, and why is it dangerous to allow it to accumulate inside your chimney?” It’s fairly easy to explain. Creosote is a sticky chemical residue—somewhat similar to watery tar—that is formed when wood is burned at lower-than-optimal temperatures and is capable of building up within your chimney, thereby decreasing the amount of open space through which exhaust gases and smoke can pass. Increased amounts of creosote are formed from burning unseasoned softwoods in your fireplace than properly seasoned hardwoods as well. The residue begins as unburned oil in the form of gas. As the gas moves up the chimney, the oils begin to form a coating inside the chimney as they cool. This buildup is a definite fire hazard.
The residue continues to build up over the course of the heating season. Depending on the internal dimensions of your chimney, this buildup can restrict the flow of air tremendously, which can lead to smoke buildup in the fireplace as well as in your house. This reduced airflow can also cause your fires to burn cooler, as they’re not able to get the necessary amount of oxygen for increased combustion; all of this results in additional creosote buildup inside your chimney. Creosote becomes dangerous when it is allowed to accumulate in your chimney because it turns into a fuel source for a possible deadly chimney fire. The build up of creosote can never be avoided completely; however, burning small, hot fires and using dry, seasoned wood can minimize the buildup.
Sooner or later, every chimney needs to be cleaned, as this is the only way to truly remove dangerous creosote buildup. It is highly recommended that you leave this task to a CSIA Certified chimney sweep to ensure that the job is done properly. The frequency for your cleanings will depend on the amount of use your fireplace receives, but it should never be any longer than a year between cleanings. Remember: a clean chimney is far less likely to catch fire than a dirty one. So what are you waiting for? Call to schedule a chimney inspection to have your chimney cleaned so you can enjoy the rapidly approaching cold-weather months with the rest of the fireplace folks.