Did Santa cause the CHIMNEY FIRE or did you just not listen to workplace safety!

“Chimneys really decorate the roofline of a home… and they’re maintenance–free, besides. Right?”  Your chimney–and the flue that lines it–adds architectural interest to your home, but its’ real function is to carry dangerous flue gases from your fireplace, wood stove or furnace safely out of your home. A chimney helps your household air stay breathable…just as your windows and your bathroom, attic and kitchen vents do. Unlike those other exhaust points in your home, however, fireplace and wood stove chimneys need a special kind of care. Chimney fires cause hundreds of deaths and millions of dollars in lost property every year.  And although a plugged chimney is bad, you really cant point the finger in safety problems with fat guy in red!

Dirty chimneys can cause chimney fires, which damage structures, destroy homes and injure or kill people. 

Few flues are stout enough to come through a severe chimney fire unscathed. There is no such thing as a "friendly" chimney fire that will safely clean out your flue. With a roar like a freight train, it can crack open flue liner and chimney and spread to the structure of the house.

"Flue fires are perennial". They happen every winter when creosote deposits on the smoke chamber and flue walls are set ablaze by high heat or by flames licking up the chimney.

A chimney fire can be exciting and light up the night, but it is NEVER a laughing matter.  Here's how it happens and why it can threaten your life and your property.

Anatomy of a flue fire

Heated wood releases hydrocarbon gases. When these get hot enough (about 1100 degrees F) they mix with air and catch fire. When hearth or woodstove fires smolder, unburned gases condense and deposit on the stovepipes and the flue as runny acids and liquid tars that harden into creosote.
Both a cool flue and steam from green or wet wood encourage this condensation.

Creosote can appear as any of the followng;
- a sooty powder
- a gummy mess
- a hard glaze
- or a deposit that looks like burnt marshmallows.
The temperature of the fire also plays a big role in creosote formation or burning. Always run a wood stove within the manufacturer's recommended temperature limits. Too low a temperature increases creosote build-up, and too high a temperature may eventually cause damage to the chimney and result in a chimney fire.

Avoid roaring fires by adding only enough fuel to keep the fire at the desired temperature. And never burn household trash, cardboard or Christmas trees in your fireplace. The sparks they produce can lead to chimney fires.

Chimney fires can be identified by sucking sounds, a load roar and shaking pipes. Fires can be controlled with minimal damage 

A creosote fire can burn with such blast-furnace intensity that it sets off this frightening chain of events: "Crumbling and cracking mortar; Balls of flaming creosote shoot out of the chimney top onto the roof; Clay-tile fluliners crack open; Stainless steel liners warp, buckle and separate at the seams; Masonry in the chimney expands with such force that sections of the chimney can blow out; flames can spread to the structure or roof of the house even explode into the room".

Other signs of structural damage include corrosion or rusting of the inner liners of metal chimneys and buckling, separation of the seam or collapsing of the inner lining of metal chimneys.

Improper installation of the fireplace or stove is another culprit of starting fires. Placing the chimney too close to wood framing or thermal insulation or improperly passing the chimney through a ceiling or wall can cause the wood framing to ignite.

 Tar-glazed Creosote

This type of creosote makes for the hottest burning fuel for a flue fire. The thicker the layer of creosote, the hotter the fire. The heat generated by this infurnal can raise to ignition point, the temperature of wood structures on the other side of a chimney, so that it also starts to burn threatening the entire house.
Wood doesn't necesarily need contact with fire in order to ignite. It just needs"air, oxygen and enough heat."

A house may survive the first chimney fire, but the intense heat has started pyrolyzing* nearby combustibles, thus lowering their ignition temperature. This makes the structure very vulnerable to a subsequent chimney fire.
A damaged flueliner can no longer protect either the chimney or the house. And instead of being all burned out, creosote may instead be all puffed up to the point of partially or completely blocking the flue.

What is *Pyrolysis

*Pyrolysis is chemical decomposition caused by heat. Severely pyrolyzed wood can ignite at only 2l2 degrees F, while it would normally have a catch-fire temperature of about 500 degrees F, before it had any exposure to intense heat.

FIRE IN YOUR CHIMNEY!!

If it happens to your chimney get everyone out of the house, because fire can flash right through the house with incredible speed. Then call the fire department from a safe distance such as a neigbours house or from your car. Do not try to put out the fire and do not hesitate leave immediately.
Afterwards, if your house is still standing, call a chimney service professional to clean and inspect the chimney as well as assess the damage. Your chimney will need to be repaired and probably relined to make it safe for further use.

No One Welcomes a Chimney Fire

A chimney fire in action can be impressive. Indications of a chimney fire have been described as creating:

• loud cracking and popping noise
• a lot of dense smoke, and
• an intense, hot smell

Chimney fires can burn explosively – noisy and dramatic enough to be detected by neighbors or people passing by. Flames or dense smoke may shoot from the top of the chimney. Homeowners report being startled by a low rumbling sound that reminds them of a freight train or a low flying airplane. However, those are only the chimney fires you know about. Slow-burning chimney fires don’t get enough air or have fuel to be dramatic or visible. But, the temperatures they reach are very high and can cause as much damage to the chimney structure – and nearby combustible parts of the house – as their more spectacular cousins.

Fireplaces and wood stoves are designed to safely contain wood-fuel fires, while providing heat for a home. The chimneys that serve them have the job of expelling the by-products of combustion – the substances produced when wood burns. These include smoke, water vapor, gases, unburned wood particles, hydrocarbon, tar fog and assorted minerals. As these substances exit the fireplace or wood stove, and flow up into the relatively cooler chimney, condensation occurs. The resulting residue that sticks to the inner walls of the chimney is called creosote.  

Creosote is black or brown in appearance. It can be crusty and flaky…tar-like, drippy and sticky…or shiny and hardened. Often, all forms will occur in one chimney system. Whatever form it takes, creosote is highly combustible. If it builds up in sufficient quantities – and the internal flue temperature is high enough – the result could be a chimney fire.  Certain conditions encourage the buildup of creosote. Restricted air supply, unseasoned wood and, cooler than normal chimney temperatures are all factors that can accelerate the buildup of creosote on chimney flue walls. Air supply may be restricted by closing the glass doors, by failing to open the damper wide enough, and the lack of sufficient make-up air  to move heated smoke up the chimney rapidly (the longer the smoke’s “residence time” in the flue, the more likely is it that creosote will form). A wood stove’s air supply can be limited by closing down the stove damper or air inlets too soon or too much. Burning unseasoned wood – because so much energy is used initially just to drive off the water trapped in the cells of the logs– keeps the resulting smoke cooler, than if seasoned wood is used. In the case of wood stoves, overloading the firebox with wood in an attempt to get a longer burn time also contributes to creosote buildup.

How Chimney Fires Hurt Chimneys 

Masonry Chimneys

When a chimney fire occur in masonry chimney – whether the flue is an older, unlined type or tile lined to meet current safety codes – the high temperatures at which they burn (around 2000°F) can “melt mortar, crack tiles, cause liners to collapse and damage the outer masonry material”.  Most often, thermal shock occurs and tiles crack and mortar is displaced, which provides a pathway for flames to reach the combustible wood frame of the house. This event is extremely dangerous, call 911 immediately.

Pre-fabricated, factory-built, metal chimneys

To be installed in most jurisdictions in the United States, factory built, metal chimneys that are designed to vent wood burning stoves or pre-fabricated metal fireplaces must pass special tests. Most tests require the chimney to withstand flue temperatures up to 2100°F – without sustaining damage. Under chimney fire conditions, damage to these systems still may occur. When pre-fabricated, factory-built metal chimneys are damaged by a chimney fire, they should no longer be used and must be replaced.  

Special Effects on Wood Stoves

Wood stoves are made to contain hot fires. The connector pipes that run from the stove to the chimney are another matter. They cannot withstand the high temperatures produced during a chimney fire and can warp, buckle and even separate from the vibrations created by air turbulence during a fire. If damaged by a chimney fire, they must be replaced.  

Nine Signs that You’ve Had a Chimney Fire 
Since a chimney, damaged by a chimney fire, can endanger a home and its’ occupants and a chimney fire can occur without anyone being aware of them it’s important to have your chimney regularly. Here are the signs that a professional chimney sweep looks for:

• “Puffy” or “honey combed” creosote
• Warped metal of the damper, metal smoke chamber connector pipe or factory-built metal chimney
• Cracked or collapsed flue tiles, or tiles with large chunks missing
• Discolored and/or distorted rain cap
• Heat-damaged TV antenna attached to the chimney
• Creosote flakes and pieces found on the roof or ground
• Roofing material damaged from hot creosote
• Cracks in exterior masonry
• Evidence of smoke escaping through mortar joints of masonry or tile liners