Your Guide to Chimney Safety



Your chimney has a big responsibility. It carries toxic gas out of your home, and while doing its job, it must withstand constant attack by acid, creosote and extreme temperatures for months on end.

These conditions cause chimney damage and deterioration, and when that happens, your
family’s safety is in question. The risks of carbon monoxide poisoning and house fires become
very real.

Look at the picture on the left. Most people would not see anything wrong with this chimney.
But there is more to the story. On the inside, the chimney could be seriously damaged and
not up to safety regulations.


Old-fashioned chimneys were not designed to vent modern heating appliances. Besides, no
​chimney lasts forever.

Because of the hostile environment, the inside of both flues of this chimney have deteriorated. Notice the cracked flue tiles (left) and the deteriorated joints and/or misaligned flues (right). According to code, both flues should be relined.
Furnace Flue
Fireplace Flue


High-efficiency furnaces do not waste energy by sending heat up a chimney. As a result, temperatures in the flue drop low enough to produce condensation. This water combines with acids in the flue to create acidic moisture. Clay liners are particularly vulnerable to this acidic moisture assault. 

Examples of damaged furnace flues are:​​

• Chimney structure deteriorating
• Eroded or missing clay liner
• Carbon monoxide leaking into home
• Joint between flue tiles not sealed

• Flaking plaster and/or peeling
• Staining on wall surfaces due to moisture
• Excessive moisture in gas or oil flues
• Excessive soot in oil furnace flues


Fireplace flues service a fireplace, wood stove, pellet stove or other solid fuel appliance. Cracks in the flue show that it may have undergone a chimney fire, or have been connected to an improperly vented appliance, misused wood stove, or exposed to excessive moisture. A damaged flue brings the dangers of fire and carbon monoxide poisoning.

Examples of damaged fireplace flues are:

• Cracked or missing tiles
• Eroded brick and mortar
• Excessive or glazed creosote
• Joint between flue tiles not sealed
• Flue tiles not aligned properly
• Improper chimney draft


Chimney fires happen when creosote builds up in the flue and ignites. These fires can rage at temperatures up to 2000 degrees and roar just inches away from your home. The intense heat alone can bring surrounding materials to the flash point, and ignite your home. Also, sparks from the fire can find their way through small cracks in the liner and quickly turn a chimney fire into a house fire.

Creosote is estimated to be involved in 14,720 (or 22%) home heating fires per year, and it is estimated to result in 4 deaths, 24 injuries and $33 million in property damage per year. (Source: NFPA)


Carbon monoxide (CO) is a colorless, odorless gas. Sometimes an early warning is flu-like symptoms, but CO can cause brain damage and death with no warning. A damaged furnace flue poses a real threat of carbon monoxide poisoning, because this gas can escape through the smallest crack. Also, a partial or complete collapse of the clay flue liner can block the
flue, and quickly fill the house with deadly gas. Sadly this tragedy occurs in homes across the country every year.

Between 2001-2003, the CDC estimates that approximately 
15,200 people treated for unintentional non-fire carbon monoxide poisoning in emergency rooms and in 2005 there
were an estimated 61,100 incidents reported, up 18% from 2003. 89% of the reported incidents took place in the home! (Source: NFPA)

Felgemacher Masonry
2727 Broadway, Suite 5
Cheektowaga NY 14227