Types of Chimney Deposits


If you follow along with this blog, you’d know that I talk a lot about creosote. Rightfully so, too. Creosote is the number one reason chimneys catch on fire

But creosote isn’t the only kind of deposit that forms inside your chimney. 

While creosote is the most dangerous, these other ones can build up enough to hinder the free flow of gases up and out of your flue if they are not removed. 

If the gases can’t flow out of the chimney, they’ll just get pushed into your living room causing smoke or carbon monoxide to fill the air. 

In this post, I’m going to give you an overview of each of the different types of common chimney deposits (including creosote).


Table of Contents


Types of Chimney Deposits


Removing Chimney Deposits


Hire a Certified Chimney Sweep

Types of Chimney Deposits

As I mentioned, the deposit you probably hear about the most is creosote. And that’s good because you need to be aware of the most common cause of chimney fires.

You can break down each of the deposits into various forms, but we like to divide them into three basic types: soot, creosote, and glaze.

Creosote Chimney Cap


You’ve heard of soot I’m sure. I knew about soot long before I had even heard about creosote. That’s the stuff that gets caught on Santa. 

Soot is primarily composed of carbon particles, but may also contain some ash

Soot has a soft texture and will be black or brown in color. 

Since carbon is combustible but ash is non-combustible, depending on the concentration of carbon and ash, soot could be flammable and needs to be cleaned out.


Glaze is a form of deposit that didn’t get the benefit of a cool name. In fact, that’s how most chimney-related things are: no cool names. 

That means it’s exactly how it sounds. It’s a deposit with a shiny, tarry substance. It can form puddles or drop down to make formations that resemble black icicles or stalactites. 

The glaze is the densest of the three deposits here. That means it represents the greatest amount of fuel to burn in the event of a chimney fire. 

That also means that it’s the most difficult type of deposit to remove from your chimney.


Last but certainly not least. Creosote is a combustible (i.e. flammable) deposit in your chimney system. It begins as condensed wood smoke, including tar fogs and vapors. 

Creosote is simply the byproduct of incomplete combustion. Since it’s nearly impossible to burn to 100% combustion, you’ll always have at least a little bit of creosote built up into your chimney as you use it. 

Creosote can be either brown or black and form curly, flaky deposits or even bubbly deposits in the venting system. 

Creosote is highly flammable and you should make sure you are taking the steps to remove creosote from your chimney. 

Read More: What is Creosote?

Removing Chimney Deposits

This is where chimney sweeps come in!

While a large part of the job is repairs, our primary job as a chimney sweep is to remove the chimney deposits and inspect your chimney to evaluate the overall condition.

A competent chimney sweep will be able to give you recommendations to help improve the safety and efficiency of your chimney and fireplace.

chimney ashes

Why Get a Chimney Sweep

I wish I could say that all Chimney Sweeps can sing and dance like Bert the chimney sweep in Mary Poppins

But we’re just not that talented. Maybe we can add that to the National Chimney Sweep Curriculum

But, don’t worry. 

There are plenty of reasons to remove your chimney deposits: 

  • Removal ensures that the appliance vents properly
  • Removal aides in preventing chimney fires
  • Removal helps reduce or completely eliminates chimney odors
  • Removal of deposits also helps get rid of any blockages that could cause carbon monoxide gases to enter your home
  • Removal of deposits can help prevent deterioration of the chimney interior caused by acids in the deposits

There is no single answer for how often you should clean your chimney. The National Fire Protection Association (NFPA) recommends that you inspect your chimney at least once a year and have it cleaned as necessary. 

The frequency that you choose to clean your chimney should depend on how much you use your chimney, the type of chimney, the type of fuel, and your burning habits. 

A good rule of thumb is that chimneys should be cleaned when accumulations of soot and creosote approach or exceed 1/8 inch. 

The best way to know when your chimney is approaching those deposit levels is with an annual inspection. 

If the chimney company you hire recommends a sweep, you’ll likely see a variety of different cleaning techniques to remove the chimney deposits: standard cleaning, mechanical cleaning, and chemical cleaning.

creosote cap

Standard Cleaning

The most common way to clean your chimney will be with a brush to clean the chimney walls.

We use a powerful vacuum with a strong filter to prevent soot and creosote from entering your home.

This cleaning is effective for soot and ordinary deposits. But it doesn’t do too much for glaze deposits.

Mechanical Cleaning

Mechanical cleaning requires that we use wire brushes, plastic cables, or special chains rotated at very high speeds.

This type of cleaning is often used to remove hard creosote or glaze deposits. Mechanical cleaning should only be attempted by professional sweeps familiar with this type of cleaning.

Failure to do so could be hazardous to the operator and could destroy parts of your chimney.

Chemical Cleaning

Some chimney companies prefer to use chemicals when cleaning. This can be used with mechanical cleaning or as a substitute of mechanical cleaning.

These chemicals are used to help loosen or dissolve heavy deposits of creosote and glaze.

Just like with mechanical cleaning, chemical cleaning should only be attempted by trained professional chimney sweeps.

Final Thoughts on Cleaning

As you can see, there are a few different methods that we can use to help keep your chimney safe.

Don’t expect a chimney sweep to recommend all of these – your chimney might only need a standard sweep. But you should hire a chimney sweep that has the ability to do all of these types of sweeps.

Quick Tips for Hiring a Chimney Company

I know, it’s a lot to consider. 

But that doesn’t mean that it has to be a stressful task. You can easily reach out to your local chimney company and have a done-for-you solution in no time!

But navigating through all of the chimney companies in your city can be a chore all on its own. And it makes sense, too. 

Hiring anyone to come into your home to fix something like your chimney shouldn’t be a task you take lightly. So I created a list that you can use to make sure you make the right decision when you need someone to help you in your home.


How to Hire, What to Look For

When you’re hiring a chimney company, you should always ask the following questions before allowing them to come into your home:

  1. Can the company provide references? 
  2. Does the company carry a valid business liability insurance policy? 
  3. Does the company ensure that a certified chimney technician will be on the job? 

If they guarantee all three of those, then you are in a good spot. The technicians don’t necessarily need to be certified by the CSIA, but I do recommend putting in a bit more due diligence before accepting a certification that’s not by the CSIA. 

This is because certifications are a tricky thing, especially in an unlicensed industry like ours. Any company can craft a list of job-related questions and sell them as an exam and certify those who pass. 


I recommend you take a few extra minutes in your research before making your hiring decision to learn more about the certification the company has. Here are a few tips to make sure the certification is reputable: 

  • Is the word “certified” just part of the business name or is it an earned designation? 
  • Is the certifying body a for-profit business or non-profit? 
  • Does the certification need to be maintained and renewed through continuing education as the industry evolves, or is it well enough to be certified through a one-time exam? 
  • Is the certifying body well-established or are they relatively new to the scene? New doesn’t mean “bad” but you should make sure the requirements for certification are more or at least equally stringent as those of more established certifications
  • Is the mission statement of the certifying body focused on educating and protecting homeowners or is it more focused on making it easier to earn a certification? 
  • Does holding the certification require following a code of ethics? 

If you can answer all of these questions, then I think it will be safe to allow the company in your home to work on your chimney.

Please note that If you are hiring a chimney company to install a cap for you, most of the time, they will need to buy the cap themselves. This is primarily for liability and insurance purposes. 

Besides, it’s probably cheaper for them to buy a cap at the dealer discount than for you to buy one at retail cost.

It doesn’t matter if you are in Roanoke, Lynchburg, Blacksburg, or some other city anywhere in the USA — if you have any questions about the safety of hiring a chimney company, please don’t hesitate to email me at mitchell@patriotchimney.net or call me at 540-225-2626. I’m happy to help!

Final Thoughts

Patriot Chimney has a few CSIA Certified Chimney Sweeps that you can trust with your home and family. During your service, you can expect your technician to inspect your chimney with a video camera so we can give a full top-to-bottom, inside out inspection. 

We’re licensed, insured, certified, and guarantee you’ll be happy with your service.



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