Chimneys are an integral part of most home heat masonry chimney is composed of several comp,, playing an important role in the performance and the chimney, regardless of the fuel utilized or the ,,,acne that is used. One of the most important, and understood, of these components is the flue lining brochure has been produced by the Chimney Safe America (CSIA) to give the homeowner or reside,,, understanding of what a flue lining is , what funk,,, forms, and the condition in which it should be for,, tained.

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Chimneys are an integral part of most home heating systems. A masonry chimney is composed
of several components, each playing an important role in the performance and function of the
chimney, regardless of the fuel utilized or the heating appliance that is used. One of the most
important, and perhaps least understood, of these components is the flue lining. This brochure
has been produced by the Chimney Safety Institute of America (CSIA) to give the homeowner or
resident a basic understanding of what a flue lining is what functions it performs, and the condition
in which it should be found and maintained.

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Flue Lining

A flue lining of a chimney is defined as “A clay, cast concrete or metal conduit installed in a
chimney, intended to contain the combustion products, direct them to the outside atmosphere, 
and protect the chimney walls from heat and corrosion “A wise homeowner will want to know about
the condition of the chimney, including the flue lining, in the home he owns or plans to buy.
This information can be supplied by a CSIA Certified Chimney Sweep. Although codes and
building practices may very from one state or locality to another, the installation of flue lining in
chimneys has been recommended since the early part of this century. It should be noted however
that many chimneys built since then have not included a flue lining.

Terra-Cotta Flue Tile

The most common material used as a lining for masonry chimneys in a new construction is terra-
cotta clay flue tile. It is a relatively inexpensive and easily obtainable product. Lining products made
of other materials, such as ceramics, metal and cast concrete, are preferred and may be used in
new construction. These alternatives are most commonly used in upgrading chimneys built
with improper linings, those with damaged or oversized linings, or those originally built without
the benefit of any type of lining.

1. Unlined chimneys allow heat to move through brick chimney walls very quickly. The unlined test chimney caused adjacent woodwork to catch fire after only three-and-one-half hours of testing. In fact, the unlined chimney performed so poorly hat testing of unlined chimneys was abandoned.
2. Clay flue tiles were easily damaged during the testing as a result of thermal shock. All of the flue tile samples subject-ed to the heat shock test suffered damage in the form of cracking.
3. It was determined that if the flue gases were allowed to penetrate to the brick and mortar, the result would be a reduction in the sable life of these components due to mortar deterioration. It is important to note the flue gases are acidic in nature and can be quite corrosive.

At the conclusion of the testing, the researchers recommended that flue linings, and the bonding material that joins them, be capable of containing flue gases and be designed to minimize condensation in the system. In fact, the researchers felt so strongly about the need for proper lining that they characterized building a chimney without a lining as “little less than criminal!”

During all of the testing, it has been consistently shown that clay tiles crack quite easily from thermal shock.
Testing has also shown that clay tile does not crack from normal usage.

Thermal Shock and liner Damage

Clay tile is a ceramic product and as such it cannot rapidly absorb and evenly distribute heat during
rapid temperature rises in the chimney. A rapid temperature rise (as during a chimney fire) will cause the
clay material to rise in temperature much more rapidly on the inside than on the outside of the tile. As the
inside heats up, it will begin to expand very rapidly, much more rapidly than the cooler outside is expanding.
This uneven heating produces and unequal expansion which in turn causes the flue tiles to crack and split
apart. This is similar to immersing a cold drinking glass in very hot water. It will shatter instantly.

Thermal shock results only during periods of rapid temperature rise or fall or when starting a hot fire in a
cold chimney. These conditions are met almost solely during what is known as a chimney fire, or when water
is introduced during a fire, rapidly cooling the tile.

Chimney Fire Characteristics
A chimney fire is defined as “combustion within the venting system of an appliance.” A venting system will
in dude the flue, the connector pipe of a heating appliance, the thimble area (the point where the
connector pipe passes in to the chimney), and the smoke chamber of a fireplace (the area between
the firebox and the flue). None of these areas were designed nor intended to accommodate combustion. Combustion in the areas causes temperatures to rise and heat the surrounding chimney structure quite rapidly. During chimney firs, the flue gas temperature may well approach and at times even exceed 2000 degrees Fahrenheit. This is more than enough to produce thermal shock and crack the flue tile.

A chimney fire may either be “free-burning” or may be classified as “slow-burning.” Afree-burning chimney fire is what normally comes to mind when we hear the phrase      “chimney fire”. Free burning chimney fires are usually noisy and dramatic enough to be detected by the home occupants or by passers-by. These fires usually cause rumbling noises from the chimney, a tinkling sound from the connector pipe, and have even been compared to the roar of a large jet aircraft flying in the vicinity. Flames may be observed coming from the top of the chimney, and at times a virtual fire-works show will occur, often drawing the attention of neighbors.

A slow-burning chimney fire, on the other hand, does not always exhibit the sights and sounds commonly associated with a chimney fire. This fire burns slowly because the supply of oxygen or fuel in the venting system is limited. A slow-burning fire is potentially more damaging to the chimney and surrounding combustibles than a free-burring fire because the areas where they occur are not venting freely. This lack of ventilation holds down the obvious signs of the fire while contributing to rapid heat build-up in the chimney.

When either a slow or a free-burning fire has occurred, certain signs of the fire may be observed. Contrary to popular belief, a chimney fire will not always clean out a chimney. Signs that a chimney fire has occurred commonly include one or more of the following:

1. Ashes from burned creosote are usually present after a chimney fire has occurred. Creosote ash will be light-weight and fragile, with a tissue paper like consistency. Often the creosote will exhibit many colors.
2. Clean areas may appear randomly in the flue. These clean areas are the result of extremely high heat build-up or possible air leakage into the chimney.
3. Metal chimney components such as dampers, chimney caps, or metal smoke chambers may be warped and/or discolored. Antennas mounted near the chimney may also be damaged.
4. Large pieces of expanded creosote may be found in gut-tars or the yard around the chimney. There may also be damage to the roof around the chimney.

It is not unusual for the occupants of a home to be unaware that a chimney fire has occurred.
Chimney numerous cases where undetected chimney fires h,,, Chimney fires may also occur
while the occupants are either asleep or away from the home. Continued use of a chimney
system which has been carries with it several hazards. These hazards including limited to:

1. A masonry chimney expands and contra,, and cools. This may cause pieces of a car, to
   fall out. As a result, the chimney become these areas and presents all the hazards
   chimney. Fallen pieces can also block the flue gases to back up into the appliance.
2. Flue gases can leak during use of the hear, One of the primary functions   of the flue,,,
   contain these products of combustion. W,,ing is cracked,these cracks open during phase
   and may allow gases to pass to the These gases, being acidic, attack the mas shorten
   the life of the masonry structure this can lead to carbon monoxide in the
3. Heat can be transferred to the vulnerable. One of the important functions of the fl,,, serve as
   an insulator between the hot flu,,, chimney wall.

May either be free burning or ma is classified nag. Agree burning chimney fire is what normally when we hear the phrase chimney fire. Free, eye fires are usually noisy and dramatic enough to the home occupants or by posses-by. These fires bumbling noises from the chimney, a tinkling sound, ctor pipe, and have even been compare to the roar, craft flying in the vicinity. Flames may be observed top of the chimney, and at times a virtual fire,,, occur, often drawing the attention of neighbors.

Chimney fire, on the other hand, does not always and sounds commonly associated with a chimney, me slowly because the supply of oxygenic fuel in bam is limited. A slow-burning fire is potentially more chimney and surrounding combustibles than a ,,,e because the areas where they occur are not this lack of ventilation holds down the obvious signs contributing to rapid heat buildup in chimney.

Jowl or a free-burning fire has occurred, certain signs are observed. Contrary to popular belief, a chimney, ayes clean out a chimney. Signs that a chimney fire has only include one or more of the following;

,,s from burned creosote are usually present after money fire has occurred. Creosote ash will be weight and fragile, with a tissue paper like stench. Often the creosote will exhibit many colors.

, n areas may appear randomly in the flue. These areas are the result of extremely high heat, -up or possible air leakage into the chimney.

L,,, chimney components such as dampers, chimney ,, r metal smoke chambers may be warped and /or ,,,lured. Antennas mounted near the chimney may be damaged.

E pieces of expanded creosote may be found in gut or the yard around the chimney. There may also be
age to the roof around the chimney.It is not unusual for the occupants of a home to be
completely unaware that a chimney fire has occurred. Chimney sweeps find
numerous cases where undetected chimney fires have occurred. Chimney fires
may also occur while the occupants of the home are either asleep or away from
the home.

Continued use of a chimney system which has been damaged carries with it
several hazards.

These hazards include but are not limited to

1. A masonry chimney expands and contracts, as it heats and cools. This
   may cause pieces of a cracked flue lining to fall out. AS a result, the
   chimney becomes unlined in these areas and presents all the hazards of
   an unlined chimney. Fallen pieces can also block the flue and cause
   flue gases to back up into the appliance and the home.
2. Flue gases can leak during use of the heating system. One of the primary functions of the flue lining is to contain these products of combustion. When a flue lining is cracked, these cracks open during the heating phase and may allow gases to pass to the chimney walls. These gases, being acidic, attack the masonry and will shorten the life of the masonry structure, In addition this can lead to carbon monoxide in the residence.
3. Heat can be transferred to the vulnerable chimney walls. One of the important functions of the flue lining is to serve as an insulator between the hot flue gases and the chimney wall.

When the chimney walls are over heated, this heat can also transfer to surrounding combustibles.

Never use a chimney that does not have a liner or has a damaged or improper lining!

A Word pf Advice
Your chimney is an important part of your home heating system. For safe and
efficient operation, your chimney should be checked annually by a CSIA
Certified Chimney Sweep and cleaned as needed .Each year, unsafe chimneys
cause significant numbers of deaths and injuries and account for more than
$200 million in property losses. Make chimney examinations a regular part of
your home maintenance schedule. Don’t become a statistic!

The Chimney Safety Institute of America (CSIA) is a non-profit educational institute
that has established the only nationally recognized certification and
accreditation program for chimney sweeps in the United States, The program
was developed in keeping with the CIA’s commitment to the safety of chimney
and venting systems and to the elimination of residential chimney fires, carbon monoxide intrusion and other chimney and vent-related safety hazards. The CSIA devotes its resources to education the public, chimney service professionals and other fire prevention specialists, and the insurance industry about the prevention and correction of chimney and venting system hazards.