What does a dirty chimney look like?

If you have ever hired a chimney sweep to sweep your chimney, you have probably heard about a dirty chimney. But, how do you know if your chimney is dirty? How do you know if your chimney needs to be swept? How do you know if the chimney sweep you hired did a good job?

First of all, let me show you a super dirty chimney. This chimney has a bunch of creosote built up inside of the flue. The owners of this chimney had SEVERAL fires too many before hiring a chimney sweep. Creosote is both corrosive (breaks down the lining) and combustible (can catch on fire). When creosote catches on fire in a chimney, that is called a chimney fire. Chimney fires are bad because the flue is not meant to withstand a fire’s temperature. It is meant to exhaust a fire’s heat. (We’ll explain more about this in a future post.)

In this picture you can see all this bumpy, flaky creosote stuck to the side of the chimney. That’s a lot. It shouldn’t be there. This view is from the top of the chimney looking down into the firebox. It’s not a view that you would likely see. Here’s another dirty chimney:

This is what we in the trade call a pre-fabricated chimney. This is a picture of a damper with a damper lock. The damper is the circular metal plate. It is intended to open and close, however when gas runs to the firebox they cannot close. The metal piece that is attached is called a damper lock, which is intended to hold a damper open. We have a little more information about damper locks here if you’re interested.

I included this picture because this is a view that you as a homeowner would see. If your damper has this kind of stuff on it, the chimney is dirty.

Here is a couple of before and after shots. (Our technicians take these sort of pictures so our customers can see what’s going on in their chimney.)

Pre-fabricated Chimney Before Sweeping

Pre-fabricated Chimney After Sweeping

See how dirty that chimney is? And then see how clean it is? That is a good example of how you can tell if your chimney sweep did his or her job. You can just look up into your chimney and see this stuff. Another option: put your phone into the firebox and take a quick picture. (This is an option if you’re not bendy enough to get your head into the firebox.)

Here is a before and after shot of a masonry chimney:

Dirty masonry chimney looking from the top of the chimney.

Clean masonry chimney looking down from the top of the chimney.

This is what we’re talking about when we say a chimney is dirty or it needs to be swept. Keep in mind, the point of sweeping a chimney is to remove all of that corrosive and combustible stuff from the inside of the chimney system. This prevents home fires. Also, keep in mind, looking at your damper is not the only way to see if you need a chimney sweep. Every single fire you light leaves a residue on the inside of your flue. Even if it doesn’t look dirty from the firebox, the flue might still be dirty. The only way to tell for sure if you need a chimney sweep is to hire a certified chimney sweep to perform an inspection.

If you hire a chimney sweep, you should be able to ask for a before and after photo. This is a good way to see how the chimney sweep did during his appointment.