When and How to Clean Your Chimney
If you have a chimney, it will need cleaning—that’s a fact. But when and how often do you have to clean your chimney? The answer depends on a number of factors, including how often it’s used, what kind of fuel you’re burning, and even what material your flue is made from.
Why Clean the Chimney?
The biggest concern is chimney fires, which occur when creosote build-up that condenses inside chimneys from wood smoke catches fire. This is most common with wood stoves but can be a problem with fireplaces as well. According to the Chimney Safety Institute of America (CSIA), chimney fires can reach 2,000F, which is hot enough to crack masonry chimney liners and potentially start a fire in the surrounding wood framing.
Tips for Keeping Your Chimney Clean
Burning well-seasoned, dry wood is one way to minimize creosote production. (Green wood burns at a cooler temperature, producing more combustion byproducts and colder smoke that’s more likely to condense in the flue.
Also, older wood stoves may be more likely to create creosote than new ones. “EPA-certified wood stoves burn more efficiently than older non-certified models, resulting in less creosote buildup in the chimney,” says the EPA. Still, the EPA, CSIA, and the National Fire Protection Association (NFPA) all say that even chimneys servicing newer wood stoves should be inspected and cleaned annually.
Chimney Cleaning for Wood, Gas and Oil Fireplaces
Any chimney that vents a fuel burning appliance, even non-wood-burning ones such as gas-fired or oil-fired boilers, furnaces, or water heaters, should be inspected by a CSIA certified chimney sweep.
Although creosote isn’t a worry with gas or oil, there are two other concerns:
- First, particularly with oil, there’s a chance of enough soot building up to block the chimney and cause deadly carbon monoxide to leak into your house.
- Second, with either fuel, some of the combustion byproducts can combine with water that condenses from the exhaust to create a solution that’s corrosive enough to damage the flue liner. Over time, that damage can be extensive enough to allow flue gasses into your home.
While wood stove chimneys and those for heavily used fireplaces should be cleaned annually, it’s likely your gas or oil chimney only needs a Level 1 inspection. The NFPA lists three levels of inspection:
- Level 1 is a just a visual check for dangerous deposits in the chimney and for structural soundness.
- Level 2 inspections are generally done only at home sales and when changing from one type of fuel to another. (Level 2 inspections also check that the chimney has the proper clearance to combustibles.)
- Level 3 inspections are done when structural damage is suspected.
DIY Chimney Cleaning
While it’s a very good idea to have the chimney inspected by a CSIA professional, serious DIYers can do some maintenance themselves. Here are the steps for cleaning your chimney yourself:
- First, take a good look at the inside of the flue. You might be able to inspect the chimney from the bottom, either by looking up from the fireplace with a flashlight, or through the cleanout with a flashlight and mirror.
- The best view is had from above, however. To do this, you’ll need to be above the chimney looking down, which means you’ll need to be able to use ladders and be on a roof safely and comfortably.
- Remove the chimney cap and shine a flashlight into the flue.
- Whether from above or below, look for damage to the flue and for build-up of a black, flak‑y substance. That’s creosote.
- If you find creosote, the chimney needs cleaning. If you spot damage, you need a pro who’s familiar with NFPA Standard 211 to make repairs.
Tools for Cleaning a Chimney
Though most people feel better off hiring a pro, with the right tools it’s possible—and even relatively easy—to clean your own chimney.
Buy a chimney brush that’s sized and shaped to fit your flue, and enough extension rods to run the flue’s entire length (rods come in 4-, 5-, and 6-foot lengths). For masonry flues, use a metal brush, and for stainless steel ones, use a poly brush.
To use a chimney brush, follow these steps:
- Close the door to the wood stove, or tape plastic across the fireplace opening.
- Working from above, with the damper open and the chimney cap removed, thread on the first rod.
- Insert the brush into the flue, push it down, scrubbing up and down as you go.
- Thread on additional sections of rod as needed and repeat the scrubbing until you reach the bottom.
- Once the brush is out of the chimney, look inside to see if you’ve removed all the creosote. If you haven’t, repeat the process.
- Once the flue is clean, use a shop vacuum to remove all the soot and creosote that’s fallen into the lower areas.