"Chimneys really decorate the roofline of a home… and they’re maintenance–free, besides. Right?"

WRONG!

Your chimney–and the flue that lines it–may add architectural interest to your home, but their real function is to carry dangerous fireplace, wood stove or furnace* gases and smoke 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. As you snuggle in front of a cozy fire or bask in the warmth of your wood stove, you are taking part in a ritual of comfort and enjoyment handed down though the centuries. The last thing you are likely to be thinking about is the condition of your chimney. However, if you don’t give some thought to it before you light those winter fires, your enjoyment may be very short-lived. Why? Dirty chimneys can be a fire hazard. Chimney fires can damage structures, destroy homes and injure or kill people.

No One Welcomes a Chimney Fire
A chimney fire in action can be impressive. It has been described variously as creating: . loud cracking and popping noise . a lot of dense smoke, and . an intense, hot smellChimney 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. With proper chimney system care, chimney fires are entirely preventable.

Creosote & Chimney Fires: What You Must Know
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 byproducts of combustion – the substances produced when wood burns. These include smoke, water vapor, gases, unburned wood particles, hydrocarbon volatile, 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 catches fire inside the chimney flue instead of the firebox of the fireplace or wood stove – the result will be a chimney fire. Although any amount of creosote can burn, sweeps are concerned when creosote builds up in sufficient quantities to sustain a long, hot, destructive chimney fire. Certain conditions encourage the buildup of creosote. Simply put, 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 supplies on fireplaces may be restricted by closed glass doors or by failure to open the damper wide enough 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 and too much, and by improperly using the stovepipe damper to restrict air movement. 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, as it moves through the system, than if dried seasoned wood is used. In the case of wood stoves, fully packed loads of wood (that give large cool fires and 8 or 10 hour burn times) also contribute to creosote buildup. Cool flue temperatures speed creosote production, too. Condensation of the unburned byproducts of combustion occurs more rapidly in an exterior chimney, for example, than in a chimney that runs through the center of a house and exposes only the upper reaches of the flue to the elements.

How Chimney Fires Hurt Chimneys
Masonry Chimneys. When chimney fires occur in masonry chimneys – whether the flues are an older, unlined type or are 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, tiles crack and mortar is displaced, which provides a pathway for flames to reach the combustible wood frame of the house. One chimney fire may not harm a home. A second can burn it down. 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 determined by Underwriter’s Laboratories (UL). 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 chimney fires can occur without anyone being aware of them…and since damage from such fires can endanger a home and its occupants, how do you tell if you’ve experienced a chimney fire? Here are the signs a professional chimney sweep looks for: . "puffy" creosote, with rainbow colored streaks, that has expanded beyond creosote’s normal form. . 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 If you think a chimney fire has occurred, call a CSIA Certified Chimney Sweep for a professional evaluation. If your suspicions are confirmed, a certified sweep will be able to make recommendations about how to bring the system back into compliance with safety standards. Depending on the situation, you might need a few flue tiles replaced, a relining system installed or an entire chimney rebuilt. Each situation is unique and will dictate its own solution.

Proper Maintenance
Clean chimneys don’t catch fire. Make sure a CSIA Certified Chimney Sweep inspects your solid fuel venting system annually, and cleans and repairs it whenever needed. Your sweep may have other maintenance recommendations depending on how you use your fireplace or stove. CSIA recommends that you call on certified chimney sweeps, since they are regularly tested on their understanding of the complexities of chimney and venting system.CSIA & Certified Chimney Sweeps

The Chimney Safety Institute of America (CSIA) is a non-profit educational foundation 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 CSIA'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 educating 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.

Ways to Keep the Fire You
Want…from Starting One You Don’t!
Chimney fires don’t have to happen. Here are some ways to avoid them. . Use seasoned woods only (dryness is more important than hard wood versus soft wood considerations . Build smaller, hotter fires that burn more completely and produce less smoke . Never burn cardboard boxes, wrapping paper, trash or Christmas trees; these can spark a chimney fire . Install stovepipe thermometers to help monitor flue temperatures where wood stoves are in use, so you can adjust burning practices as needed . Inspect and clean catalytic combustors on a regular basis, where applicable

What to Do if You Have a Chimney Fire
If you realize a chimney fire is occurring, follow these steps:
- Get everyone out of the house, including yourself
- Call the fire department.If you can do so without risk to yourself, these additional steps may help save your home. Remember, however, that homes are replaceable, lives are not:
- Put a chimney fire extinguisher into the fireplace or wood stove . Close the glass doors on the fireplace . Close the inlets on the wood stove . Use a garden hose to spray down the roof (not the chimney) so the fire won’t spread to the rest of the structure.

Once it’s over, call a CSIA Certified Chimney Sweep to inspect for damage. Chimney fire damage and repair normally is covered by homeowner insurance policies.

What you don’t know about your chimney can hurt you – especially if you have a gas-heating appliance that uses your masonry chimney as a venting system. Every day, without any visible signs, acid produced by your gas appliance may be eating away at the inside of your
chimney. The resulting damage can compromise the safety of your family and the value of your home. But thorough annual inspection of your chimney, as recommended by the National Fire Protection Association and the Chimney Safety Institute of America, can alert you to potential problems before they become costly or dangerous.

Most homeowners are aware of the need for chimney cleaning and inspection if they own a wood-burning stove or regularly use their fireplace. But many don’t realize that gas heating appliance – whether it is a furnace, boiler or even a hot water heater – relies on the chimney for proper venting of the exhaust. Appliances fueled by natural gas or propane may not produce the visible soot that appliances burning other fuels do, but they can deposit corrosive substances in your chimney. In many cases, these acids may wreak havoc on your chimney without producing any external symptoms until the problem has become dangerous or expensive to repair.

The Best Safeguard: Annual Inspections
Gas heating appliances are one of the most popular choices for home heating in many areas of the country. Natural gas is a relatively inexpensive fuel and new, higher efficiency appliances help keep fuel consumption down. With new natural gas pipelines being put in across the country, this economical option is becoming available to more and more people. The combination of an inexpensive fuel and a higher efficiency appliance is great for your wallet. But in order to work as safely and efficiently as possible, gas appliances must meet specific venting requirements. One of the best ways to ensure that your gas heating appliance will operate correctly is to have a CSIA Certified Chimney Sweep evaluate the chimney at the time the appliance is installed.

An evaluation will provide information that will result in a better match between the heating appliance and the chimney. It will also give you and the chimney professional a point of reference to determine any changes in the chimney at subsequent yearly evaluations.If the chimney was not inspected at the time the appliance was installed, it is important to have the chimney-heating appliance relationship checked out. Evaluations are especially important when older chimneys are paired with higher-efficiency appliances and boilers–generally, those with efficiency ranges above 80 percent - but are also important with new chimneys and older heating appliances. (Appliances with efficiency ranges of 90 percent do not require vertical vents and are vented horizontally through an outside wall).

Special Venting Considerations
Today’s higher efficiency appliances use most of the heat that is produced by combustion to heat your home. Every homeowner wants to prevent heat that could be used to warm the home from escaping up the chimney. What many don’t realize it that is that some amount of heat is necessary in order to provide the draft that makes a venting system work. Because there is less heat in the venting system with higher-efficiency appliances, the heating and venting system must be properly matched in order to achieve the safest and most efficient operation. Improper matches often occur when flues or the connector pipes are too large.Gas is widely marketed as a clean-burning fuel, and under optimum conditions, that’s true. However, in order to burn the gas, your heating appliance must take in air for combustion. The same acids in the air that cause acid rain may also be present in the air your heating appliance takes in. The air may also carry chlorides – often picked up from household cleaning products or other pollution. When chlorides combine with water, hydrochloric acid is formed. Other acids may form if water mixes with residues in the flue, or with other air-borne pollutants.Water vapor is always produced during combustion. In
fact, burning one cubic foot of gas yields two cubic feet of water vapor. When the heating appliance and venting system are properly matched, the water vapor is carried out of the system quickly enough and at a warm enough temperature that it does not condense inside the flue. If there is not enough heat, the water vapor will turn to liquid inside the flue. It is that acidic condensation that can deteriorate the inside of the flue.Eventually, corrosion caused by water condensing inside
the flue could cause the liner to crumble. Debris from the liner could create a blockage in the chimney that could prevent prevent carbon monoxide from leaving the system and allow it to enter your home. If the chimney is unlined or in poor condition this is especially dangerous.

The Importance of Draft
A proper heating appliance/venting system match will help ensure adequate draft in the system. Draft is important for a number of reasons. Inadequate draft can reduce the efficiency and safety of the appliance. Complete combustion requires oxygen – combustion of one cubic foot of natural gas requires more than 10 cubic feet of air to provide sufficient oxygen. Adequate draft ensures that enough air is pulled into the appliance for complete combustion. Incomplete combustion is also responsible for the production of carbon monoxide in the first place. If the appliance brings in the required amount of oxygen for complete combustion, carbon dioxide (CO2) is produced instead. The less complete the combustion, the greater the amount of carbon monoxide produced and the less heat delivered to the home.Anything that interferes with the draft can cause more
moisture to remain in the flue.

Sometimes the chimney flue is too large for the appliance’s venting requirements, giving the gases more opportunity to cool and condense inside the flue. An exterior chimney, because it is cooler, will make the problem worse. The same problems can also rise if the connector pipe that joins the appliance and the chimney is too long, or if there are too many bends or elbows in the venting system. Any of these situations could allow moisture to condense inside the flue instead of being carried out of the venting system. Older, unlined chimneys are the most susceptible to corrosion partly because of their age – simply having been used for so many years. There is also a possibility that the chimney had been used to vent appliances using differentfuels in the past and any soot deposits left behind by those fuels can speed up the corrosion of the chimney’s interior. Chimney flues that are unlined, oversized or deteriorated can usually be lined with a UL listed lining system approved for gas appliances.

A CSIA Certified Chimney Sweep can provide more information about chimney liners.

The Symptoms
Although your chimney may be suffering from an improper heating/venting match without producing any visible symptoms, sometimes the excess moisture produced causes visible results. Any of the following symptoms could point to a venting system that is not matched to your heating
system:
. Damp patches on interior walls or exterior walls
. Peeling wallpaper
. Blistered paint
. Stains on the ceiling
. White stains (efflorescence) on outside of the masonry chimney
. Eroded mortar joints
. Crumbling bricks

Although older chimneys are more likely to suffer, new chimneys are not impervious to the damage that can occur venting gas appliances. Whether the chimney in your home is old or new, the National Fire Protection Association and the Chimney Safety Institute of America recommend annual inspections of all chimneys, no matter what type of appliance they vent. There are some chimney liners that are not compatible with gas appliances because of the material from which they are made. It is important to make sure that the lining system you purchase – or even the one that may currently be in your chimney – is appropriate for use with gas appliances. Make sure that your furnace was installed according to the manufacturer’s installation instructions and the National Fire Protection Association Standards. The two most important NFPA standards that apply to gas appliances are NFPA54 and NFPA211. Your appliance’s installation manual should give you all the necessary information.