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.

what you need to know

What’s the Big Deal about a Little 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.

Other than through your chimney, you can ingest creosote through your food and water. This will cause a burning sensation inside of your mouth. Children are also extremely dangerous around creosote because they do not understand the harm.  When they play around the fireplace and creosote gets on their hands, they can then spread it when they rub their face or put their hands in their mouth.  People with health problems will experience worse symptoms if they come into contact with creosotes.  However, some medicines come with creosote as an ingredient, such as dandruff and psoriasis medication.

If you are forced to be around creosotes, take proper precaution.  Wear long clothes and accessories such as gloves and a mask.  When washing these clothes, make sure to keep them separate from everything else to keep them from spreading.  Having creosotes touch your skin can lead to serious skin irritation.

A Little Creosote Begets More Creosote…

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 rises up the chimney, the oils begin to condense and form a coating inside the chimney as they cool. Creosote is extremely flammable, and is one reason sweeps remove it during your annual chimney inspection.

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.

The Three Stages of Creosote

The build-up of creosote inside your chimney occurs in three stages, with each stage becoming more dangerous and harder to remove from the previous one.


  1. Stage 1: The first stage of creosote is the most manageable type to get rid of (as it can be easily cleaned by a trained chimney professional). At this stage, the creosote appears in the form of flaky soot. Identifying the creosote at an early stage is best time to contact a professional sweep for an inspection and cleaning.
  2. Stage 2: After it’s had some time to build up, the flaky creosote begins to harden on to the chimney liner, becoming more difficult to clean off. Even after it reaches stage two, a professional sweep can remove the creosote, but it requires more than just a brush to clean off.
Creosote from Chimney - Albany NY - Northeastern

3. Stage 3: Once the creosote in your chimney reaches stage 3, it becomes extremely dangerous for your home. Creosote at Stage 3 appears shiny and is also known as glazed creosote. Removing glazed creosote may require comprehensive treatment or repairs, as it has become fully stuck to the inside of your chimney.

Schedule an Inspection Before It’s Too Late

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.

It’s important to remember that a clean chimney is far less likely to catch fire than a dirty one. Call the certified professionals at Northeastern Chimney to schedule an appointment to have your chimney cleaned or if you have any questions about the services we provide. We can help set you at east, thereby allowing you to enjoy the cold-weather months with the fireplace-owning public.