Safety Info.

"But my furnace chimney looks fine on the outside."
Many chimneys venting gas or oil furnaces or hot water heaters may appear to be in fine condition on the outside. But inside it could be a completely different situation. Yesterday's chimneys were not designed for venting today's more energy efficient appliances. Let's take a close look at what really counts...the inside.

Now look inside, see the problems?
A look at the inside of this same chimney shows how acid-laden residue from the furnace has attacked this flue. The original clay liner has eroded away; pieces of it are even missing. (Old chimneys might not even have a liner.) Mortar and bricks are loose and falling, and moisture has leeched through to the home's interior walls.

With continued use, more erosion will take place, possibly leading to leaks in the flue, complete flue blockage, or possibly even carbon monoxide poisoning of the home's occupants. 

Chimney problems can cause illness and even loss of lives.
It's happened thousands of times - illness, even death, from carbon monoxide or sulfur dioxide poisoning. With deterioration of the flue, the deadly gases can find their way into your home through even the smallest cracks.

In severe cases, the chimney erosion will lead to partial or complete internal collapse, blocking the flue and sending these poisonous gases into the home.

But fortunately, the problems of a deteriorating gas or oil furnace flue can be corrected without completely rebuilding your chimney.