6 Tips for Inspecting a Chimney Flue

Following these 6 tips for inspecting a chimney flue will help ensure the safety of your home and family. A cracked or clogged chimney presents risks of carbon monoxide poisoning or fire. It is important to examine your chimney flue from top to bottom and cleaning it out may require specialized equipment. The Chimney Safety Institute of America certifies contractors to help you if you have concerns or discover that your chimney needs repair.

1 - Inspect Regularly

At minimum, you should inspect your chimney flue at the beginning and end of fireplace season. Periodic inspections will uncover minor problems before they turn into major ones. Cleaning out creosote build-up or repairing a crack is easier than rebuilding the chimney after it collapses or catches fire.

2 - Come Prepared for a Thorough Inspection

You will need the following tools:

  • Flashlight
  • Safety glasses and dust mask
  • Drop cloth
  • Wire brush
  • Shop vac
  • Ladder
  • Extension cord

Inspect the chimney when it is cool, after cleaning out the firebox and ash pit.

3 - Know What to Look For

Your flue liner might be made of sheet metal, clay tiles, or cast-in-place concrete. If it is clay or concrete, check for cracks on the surface. These cracks could allow exhaust gases or sparks to escape into the building. If the flue liner is metal, check for signs of warping. Look for signs of smoke escaping through joints or liners. Regardless of the material used, you will find creosote deposits on the inside of your chimney. Creosote is a condensate byproduct of incomplete combustion of volatiles in smoke. Creosote is highly flammable and can result in chimney fires if left to accumulate. You must clean the creosote from your flue when the deposits are more than 1/8 inch thick. Smooth, black creosote is more dangerous than flaky brown creosote. If the creosote is puffy or rainbow-streaked, this is a warning that a chimney fire may have already occurred.

4 - Inspect from all Angles

Place the drop cloth in the firepit and put on your goggles and mask before looking up the chimney flue. Operate the damper while looking up to make sure that it opens and closes properly. You must also inspect the chimney from above, so access the roof with a ladder if it is safely possible.

5 - Clean if Possible

You can remove some of the creosote deposits using a wire brush and a shop vac. Your chimney may have a smoke shelf above the hearth but inside of the flue. This shelf will catch the droppings that you scrape off from above. Therefore, your vacuum’s hose must be able to reach this shelf from the top of your chimney.

6 - Hire Certified Chimney Sweep if Necessary

If you cannot complete the inspection yourself or discover evidence of a chimney fire or cracking, hire a licensed contractor. The Chimney Safety Institute of America certifies chimney sweeps to evaluate and manage the hazards of fires, gas leaks and structural damage. Cracks to the flue liner may have been caused by poor construction methods which failed to address thermal expansion. They could also result from the building's foundation shifting as it settles. Either way, you must rebuild the chimney.