Chimney flues are the tubes that carry smoke from a fireplace or furnace out of the building to the top of the chimney. They are typically lined, either with ceramic flue tiles or metal. Regular cleaning of a chimney flue is important, especially if it vents a wood fireplace. Burning wood releases creosote, which is deposited inside the flue and can ignite, causing a chimney fire that can permanently damage the chimney and flue liner. Cleaning a flue is a strenuous job and involves climbing up onto the roof.
Cover the fireplace with a dust sheet and tape the cloth down tightly. This will prevent the dust scraped from the flue from spreading through the house.
Buy a wire flue brush in a size and shape that matches your flue.
Open the outside bottom clean-out door on your fireplace, if there is one. This will allow the dust from the flue to escape outside.
Set a ladder up outside of the house and climb up to the chimney with your flue brush, an extension handle, a flashlight and a bucket.
Remove the cap from the chimney and mount the flue brush on the handle.
Put on safety goggles, a dust mask, gloves and clothes that you can ruin with black dust.
Push the flue brush into the flue and scrub up and down the liner while turning the handle to give it maximum abrasiveness. This will loosen the build-up in the flue and send some of it falling to the bottom. The rest will attach to the brush; bring it out of the flue and dust it off into a bucket regularly. Keep looking into the flue with a flashlight to check cleanliness.
Climb back down the ladder when you have finished scrubbing the flue. Re-enter the house and carefully remove the dust sheet from the fireplace. Use a shop vacuum to clean up the powder from the flue; a regular vacuum will clog and could be damaged by the fine dust.