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 through 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 cause chimneyfires, which damage structures, destroy homes and injure or kill people.

Chimney fires can burn explosively – noisy and dramatic enough to be detected by neighbors or passersby. 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 air plane. However, those are only the chimney fires you know about. Slow-burning chimney fires don’t get enough air or have enough fuel to be as 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, chimneyfires are entirely preventable.

CREOSOTE & CHIMNEY FIRES: WHAT YOU MUST KNOW

Fire places and wood stoves are designed to safely contain wood-fueled fires, while providing heat for a home. The chimneys that serve them have the job of expelling the by-products of combustion – the substances given off when wood burns.

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- 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, 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: The air supply 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 firewood: Because so much energy is used initially just to drive off the water trapped in the cells of the logs – burning green wood keeps the resulting smoke cooler, as it moves through the system, than if dried, seasoned wood is used.

Cool flue temperatures: In the case of wood stoves, fully-packed loads of wood (that give large cool fires and eight or 10 hour burn times) contribute to creosote buildup. Condensation of the unburned by-products of combustion also 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 DAMAGE 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. Enough heat can also conduct through a perfectly sound chimney to ignite nearby combustibles.

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 (U.L.). Under chimney fire conditions, damage to these systems still may occur, usually in the form of buckled or warped seams and joints on the inner liner. When pre-fabricated, factory-built metal chimneys are damaged by a chimney fire, they should no longer be used and must be replaced.

The U.S. Consumer Product Safety Commission, reports that some 23,600 residential fires in the 50 states were related to solid fuel appliances and equipment in 1996. An additional 5,500 fires were attributed to chimneys and chimney connectors serving heating systems burning liquid and other fuels. As a result of these fires, 130 people died, 230 people were injured, and total property losses were set at more than $184.4 million.

In addition there were a minimum of 119 deaths from carbon monoxide and at least 4,700 “injuries” reported for the same time frame, though most estimates range much higher. The root cause of most of these losses is that most U.S. homeowners are unaware that chimneys are an integral part of a home heating system and that they require regular evaluation and maintenance. In a great many European countries – including Sweden, Norway, Denmark, Finland and Germany – chimney-fire damage statistics have been reduced to negligible numbers because national coalitions of government, insurance companies, fire and building officials, and chimney sweeps have developed tough regulations mandating regularly scheduled chimney inspections and cleaning. The citizens of those countries understand the hazards of unmaintained chimneys, and their chimney sweeps are regular members of their home safety team.

Most homeowners in the U.S. and Canada, however, seem to have little working knowledge of chimney and venting systems. This situation is complicated by the fact that faults, damage and problems rarely visible to the casual observer. In fact, people who will quickly replace a faulty automobile exhaust system because of the hazard it presents will allow their home’s exhaust system the chimney or vent – to go unchecked and unmaintained for years. The threat of chimney fires and unsafe indoor air quality conditions can be greatly reduced, perhaps even eliminated, if homeowners only understood that chimneys are active home operation systems which require regular maintenance.

THE CHIMNEY SWEEPS ROLE

The primary job of a chimney service professional is to aid in the prevention of fires related to fireplaces, woodstoves, gas, oil and coal heating systems and the chimneys that serve them. Wood burning heating systems, in particular, require careful monitoring and skillful operation.

Chimney sweeps install, clean and maintain these systems, evaluate their performance, prescribe changes to improve their performance, and educate the consumer about their safe and efficient operation. The basic task of a chimney sweep is to clean chimneys. Cleaning means removing the hazard of accumulated and highly combustible creosote produced by burning wood and wood products.

It means eliminating the build-up of soot in coal- and oil-fired systems, it means getting rid of bird and animal nests, leaves and other debris that may create a hazard by blocking the flow of emissions from a home heating appliance. In doing their primary job, sweeps also function as on-the-job fire prevention specialists. They are constantly on the lookout for unsafe conditions that can cause home fires or threaten residents with dangerous or unhealthy indoor air quality.

Interstate Ventilation specializes in chimney maintenance. A properly vented chimney promotes safety in the home, aids fire prevention and maximizes the safety and energy efficiency of home appliances. Chimney sweeping and the maintenance of venting systems for gas, oil, wood, and coal home heating appliances are essential to proper chimney maintenance. Interstate Ventilation performs maintenance in accordance with National Fire Protection Association standard (NFPA 211) for chimneys, fireplaces, vents, and solid fuel burning appliances.

Interstate Ventilation offers service by certified, professional, licensed and insured Technicians. Our technicians are abreast of all current developments in the area of venting. Interstate Ventilation Technicians employ new innovative tools and cleaning techniques. Interstate Ventilation performs maintenance in accordance with National Fire Protection Association standard (NFPA 211) for chimneys, fireplaces, vents, and solid fuel burning appliances, and specific state and local codes where applicable.

Chimney maintenace includes but is not limited to:

Regular Scheduled Chimney Inspection
Regular Scheduled Chimney Sweeping

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 a gas heating appliance-whether it is a furnace, boiler or even a hot water heater-also 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 Problems

The problems lie with the modern higher efficiency appliances. These appliances gain their higher efficiency by extracting the heat that used to be sent up the chimney and delivering it to your home instead. No one wants to waste heat up the chimney, but a certain amount of heat is necessary in order to provide the draft that makes the venting system work, and to keep the chimney walls warm enough to prevent condensation of the flue gases. If the flue temperature becomes too low, as is often the case with modern appliances, two separate but interrelated problems- incomplete combustion and water condensation- can occur.

Incomplete combustion:

The chimney is responsible not only for simply letting the combustion byproducts passively escape up the flue, but it also generates draft that actively pulls combustion air into the appliance. In fact, burning one cubic foot of natural gas requires 10 cubic feet of air to provide enough oxygen for complete combustion. If the chimney is too cool to create adequate draft, thereby not providing enough combustion air, not only does efficiency suffer, but the appliance can produce carbon monoxide, and this carbon monoxide is less likely to be safely exhausted from a chimney with a weak draft signal.
Condensation:

The second and most obvious problem from cool chimney temperatures is the condensation of water vapor inside your chimney. As odd as it may seem, the combustion of any hydrocarbon-and gas is a hydrocarbon-results mainly in carbon dioxide and water vapor. In fact the average furnace puts about 1 1/2 gallons of water into your chimney every hour! The high stack temperatures of the older inefficient furnaces kept this moisture from condensing inside the chimney, and it was often visible as steam escaping from the chimney top. Because the newer high efficiency furnaces now steal this extra heat from the chimney, all this water now often condenses inside the cooler flue.

The problem becomes even more complicated however because this water is also usually highly acidic and corrosive. The air used for combustion is generally contaminated with not only normal air pollution, but often with household cleaning products, especially chlorine from bleach. If the chimney was previously used to vent coal or oil there are most likely also sulfur deposits left inside too.So now not only do you have a gallon or more of water an hour in your chimney, you now have a gallon or more of dilute hydrochloric or sulfuric acid eating away at the mortar and brick of your chimney from the inside!

The situation is aggravated by cold exterior chimneys and long runs of connector pipe between the furnace and the chimney. 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 problem.

Damp patches on interior walls or exterior walls
Peeling wallpaper
Blistered paint
Stains on the ceiling around the chimney
White stains(efflorescence) on the outside of the masonry chimney
Eroded mortar joints
Crumbling bricks
Eventually corrosion caused by this acidic water condensing inside the flue may cause the liner, mortar, and brickwork to flake and crumble. Chimney sweeps often find this debris creating blockages in the flue, potentially exposing the occupants of the home to carbon monoxide and other dangerous combustion byproducts, a situation not to be taken lightly.

Solutions

The first step is to have the chimney/venting system evaluated by a Licensed chimney company, someone who understands the relationships between furnace and chimney type. A qualified sweep can offer advice and recommend measures to make your entire system function safely and efficiently.

If a problem is found, the solutions often involve installing a correctly sized, insulated liner, and/or reworking the connector pipe between furnace and chimney. These upgrades are designed to resize the flue for better draft, minimize the condensation, and contain the acidic byproducts within the liner to protect the surrounding masonry.

A few dollars spent on corrective measures could save thousands in expensive chimney repair down the road, and will help protect your home and family.

Consumer confidence in the convenience and safety of today’s home heating systems is usually well-placed. The oil and gas heating industries have achieved impressive safety records. Nonetheless, according to the U.S. Consumer Product Safety Commission, over 200 people across the nation are known to die each year from carbon monoxide poisoning caused by problems in the venting – out of their homes – of toxic gases produced by their heating systems. Other estimates for total accidental CO poisioning are much higher. The Journal of the American Medical Association, (JAMA Volume 261, No.8, February 24,1989) estimates 1,600 deaths occur yearly.

In addition, around 10,000 cases of carbon monoxide-related injuries are diagnosed each year. Because the symptoms of prolonged, low-level carbon monoxide poisoning mimic the symptoms of common winter ailments (headaches, nausea, dizziness, fatigue, even seasonal depression), many cases are not detected until permanent, subtle damage to the brain, heart and other organs and tissues has occurred. The difficulty of diagnosis also means the numbers of people affected may be even higher.

WHAT IS CARBON MONOXIDE?

By now we all know that carbon monoxide is a very dangerous, colorless, odorless gas, generally associated with your home heating system, but for a little better understanding, let’s take a quick trip back to high school chemistry class. The gas or oil you burn for home heating are compounds known as hydrocarbons (hydrogen + carbon). In your furnace these hydrocarbons are mixed with oxygen from the air in your home, and burned to produce heat.. When your furnace and chimney are working properly, the gas or oil is burned more or less completely, and the resulting fumes are mainly carbon dioxide(carbon + 2 oxygen atoms) and water vapor. If your furnace doesn’t get enough oxygen, either because the house is too tight or the chimney isn’t functioning properly, carbon monoxide (carbon +1 oxygen atom) is produced instead. It’s the lack of that one little oxygen atom that causes all the trouble.

WHAT CARBON MONOXIDE DOES TO YOU

Too much carbon monoxide in your blood will kill you. Most of us know to try to avoid this. Less well known is the fact that low-level exposure to this gas also endangers your health.
One of the imperfections of our human bodies is that, given a choice between carbon monoxide and oxygen, the protein hemoglobin in our blood will always latch on to carbon monoxide and ignore the life-giving oxygen. Because of this natural chemical affinity, our bodies – in effect – replace oxygen with carbon monoxide in our bloodstream, causing greater or lesser levels of cell suffocation depending on the intensity and duration of exposure.
The side-effects that can result from this low-level exposure include permanent organ and brain damage. Infants and the elderly are more susceptible than healthy adults, as are those with anemia or heart disease.
The symptoms of low-level carbon monoxide poisoning are so easily mistaken for those of the common cold, flu or exhaustion that proper diagnosis can be delayed. Because of this, be sure to see your physician about persistent, flu-like symptoms, chronic fatigue or generalized depression.
IF YOU SUSPECT A PROBLEM

If you ever suspect a carbon monoxide problem, immediately open doors or windows to ventilate the house and get everyone outside for fresh air. Most utility companies will respond to emergency calls and check your house and heating system for the presence of carbon monoxide. Do NOT reinhabit the house until you are certain there is no longer a problem. If necessary seek medical attention, treatment is very important. Have the heating system and the chimney checked and serviced by reputable professionals as soon as possible.

WHY IS POISONING FROM CARBON MONOXIDE ON THE RISE?

1) A Todays houses are more air tight due to energy conserving measures. Consequently there is less fresh air coming into a home and not as many pathways for stale or polluted air to leave it. When furnaces and boilers are starved of the oxygen needed to burn fuels completely, carbon monoxide is produced. Many newer houses are so airtight that powered exhaust fans in the kitchen and bathroom can overcome the draft in the furnace chimney and literally pull the toxic gases into the living space.

2) A The new high-efficiency gas and oil furnaces,when hooked up to existing flues, often do not perform at an optimum level. The differences in performance create conditions that allow combustion byproducts to more easily enter home living spaces.

3) A The above conditions join a number of older, on-going problems including damaged or deteriorating flue liners, soot build-up, debris clogging the passageway, and animal or bird nests obstructing chimney flues.

WHY CHIMNEY MAINTENANCE IS IMPORTANT

When gas and oil burn in vented heating systems, the dangerous fumes that are the by-products of combustion – including carbon monoxide – are released into the chimney through a connector pipe. Funneling these fumes out of the living area is the primary purpose of a chimney. In addition to carrying off toxic gases, chimneys also create the draft (flow of air) that provides the proper air and fuel mixture for efficient operation of the heating appliance. Unfortunately, many chimneys in daily use in homes throughout the country either are improperly sized or have conditions that make them unable to perform their intended function.

GAS

Natural gas is a clean-burning fuel, but todays high-efficiency gas furnaces pose special problems. (see the pages on GAS for a more complete discussion) The fumes they produce are cooler and contain high levels of water vapor, which cause more condensation than older models. Since these vapors also contain chlorides picked up from house-supplied combustion air, the flues are subjected to more corrosive conditions than before and can quickly deteriorate or plug up completely.

OIL

Oil flues need to be cleaned and inspected annually because deposits of soot may build up on the interior walls of the chimney. The amount of soot depends on how well tuned the furnace is and whether the house provides sufficient air for combustion. Excessive soot causes problems ranging from inefficient furnace operation to completely blocked chimneys.

To the extent that problems with either of these heating systems interfere with the flow of toxic gases and particles out of the house, they may also force carbon monoxide into the home. They may cause a one-time, high-level exposure situation or release smaller amounts more regularly over a longer period. These problems should never be ignored.

PREVENTING PROBLEMS

In the United States, numerous agencies and organizations now recognize the importance of annual heating system inspection and maintenance in preventing carbon monoxide poisoning. The U.S. Consumer Product Safety Commission, the U.S. Environmental Protection Agency, the National Fire Protection Association, the American Lung Association – are some of the organizations that now encourage the regular maintenance of home heating systems and their chimneys in order to keep “the silent killer” at bay.

A well tuned furnace or boiler, connected to a venting system or flue that is correctly sized, structurally sound, clean and free of blockages, will operate efficiently and produce a warm and comfortable home. Carbon monoxide detectors are now readily available and no home should be without at least two, one near the furnace and one near the sleeping area of the home. Detectors are NOT a substitute for routine maintenance, but can be a lifesaver should problems occur.

Considering the risks involved when gas or oil systems are neglected, and the benefits that accrue when they are properly maintained, we suggest you have your furnace serviced yearly by a qualified technician and your chimneys inspected and cleaned or repaired as needed.

When most people think of chimneys, they think of fireplaces. Memories of cold winter evenings, relaxed and cozy in front of a crackling fire are hard to beat, and the ability of an open fire to soothe the wild beast within us all is legendary. Since the dawn of time, humans have gathered around the open fire for a sense of safety and community, and the fireplace is still the focus of family living in many homes, especially around the holidays.

But in spite of all the glowing aesthetics, there are some practical considerations. When your dealing with an element as capricious and potentially dangerous as fire, knowledge really is power, so please read on to learn how to make your fireplace both safer and more enjoyable.

Let’s start with a quick anatomy lesson, and a brief explanation of commonly used terms:

Fireplaces come in two general types, masonry fireplaces built entirely of bricks and mortar, and factory built fireplaces consisting of a lightweight metal firebox and a metal chimney. (There are a few hybrids too, the most common being a heavy metal firebox and smoke chamber coupled to a regular brick chimney). To figure out which you have will take only a moment of detective work on your part.

A masonry fireplace has a firebox built of individual generally yellowish firebrick, a brick chimney above the roof, and if you look up past the damper you will see a roughly pyramid shaped affair also built of brick. A prefab fireplace generally has a firebox of cast refractory panels, and usually some metal is visible in the room all around the firebox. If you look up past the damper you will see a round metal chimney. And above the roof is more round metal chimney, sometimes surrounded by a simulated brick housing.

MASONRY FIREPLACES – some special considerations

Masonry fireplaces, built entirely of brick and mortar, are massive structures often weighing between 6 and 7 tons! They are aesthetically pleasing, long lasting, and add real value to your home. With a little care and periodic maintenance they can literally give you a lifetime of enjoyment.

Masonry fireplaces require an extensive footing capable of supporting their great bulk, and if not provided with one will often shift and crack, allowing the fire to escape to nearby combustibles. You should always keep an eye out for any signs of settling or movement. Just inside the firebox, where the facing material meets the firebrick, is one weak spot where this settling is often first apparent. Keeping downspouts directed away from the fireplace and careful sloping of the ground around the fireplace to be sure water runs away from the structure can keep settling problems to a minimum.

Although masonry is quite durable, and in fact is often seen as indestructible, this is certainly not the case, especially for a chimney. While the rest of the brick on the house is somewhat protected by the eave, the poor chimney is sticking up like a flagpole, exposed to every raindrop and freeze/thaw cycle. A quality chimney cover, keeping the crown in good repair, and a waterproofing treatment, are money well spent to avoid expensive repairs or rebuilding. See the section on waterproofing for a more detailed explanation.

The firebox of course takes the brunt of the fires’ heat and it requires some special attention. The firebrick can take the heat pretty well, but the fireclay joints will fail in time from the constant expansion and contraction. In a fireplace without a chimney cover, the rain water will also pool on the smoke shelf, mix with the soot behind the damper, and form an acidic slurry that seeps into the fireback destroying the mortar joints. These joints must be kept in good repair with a high temperature refractory mortar to insure the fire is contained.

The tile liners used in most masonry fireplaces are just fine as long as the fireplace is properly maintained and not exposed to chimney fires. One good chimney fire will usually crack these tiles, rendering them incapable of performing their intended function. The general rule of thumb is that a masonry fireplace should be cleaned before 1/4″ of soot accumulates. If you ever do experience a chimney fire, it is very important to have the chimney cleaned and carefully evaluated before it is used again.

Unlike prefabricated fireplaces which are factory engineered products, a masonry fireplace is built on site brick by brick, giving the mason ultimate control of the final product. This results in a wide range of masonry fireplaces available, from long lasting, heat producing beauties, to smoky pits that crumble in a relatively short time. Most masonry fireplaces that chimney sweeps encounter, although far from perfect, can, with a little tender loving care, and carefully considered maintenance procedures, provide you with many peaceful, relaxing hours in an otherwise often hectic world.

PREFABRICATED FIREPLACES

Factory built, or prefabricated fireplaces, are relative newcomers to the fireplace scene, commonly available only for the last 25 years or so. Unlike traditional site-built masonry fireplaces, most factory built fireplaces are made of metal, and come from the factory as complete units with a firebox, a specific chimney system, and all miscellaneous parts. With proper installation and maintenance, they can give years of service, but there are some special considerations owners of these systems should be aware of:

1) The factory-built fireplace and chimney are a complete system, engineered to work safely and efficiently together. Both units(fireplace and chimney), undergo testing together, then are listed specifically for use with each other. To insure a safe system, you MUST use the exact chimney specified, along with the specified rain cap, flashing package, and all other system components.

2) The installation instructions must be followed exactly, especially the specified clearances from the firebox and chimney to any combustible materials. Most manufacturers require 2″ minimum air space (no insulation allowed either), between the chimney components and all wood framing. If you are installing a new unit be sure these clearance instructions are strictly adhered to. If you have a unit already installed it is very important you check these clearances wherever possible. Any wood that is too close to the chimney will continue to dry and undergo a process called pyrolisis. It can eventually catch fire at temperatures as low as 200 degrees. Over half of the units inspected by chimney professionals are improperly installed, and a trip to the attic to check clearances is definitely time well spent! It is much more difficult to inspect the firebox clearances, but we suggest you consider installing an access port to both check these clearances and monitor the units condition as the years go by.

3) Most factory built fireplaces are tested and listed as decorative heating appliances and will not withstand the abuse often heaped on their masonry counterparts. Although they are tested to U.L. standards, severe overfiring and chimney fires will often badly damage these units. Regular yearly maintenance, cleaning at generally 1/8″ buildup, and careful monitoring can assure a safe enjoyable system.

4) Many prefab chimneys, especially older units with an imitation brick housing above the roof, seem to be a preferred nesting site for birds in many areas. It is not unusual for chimney sweeps to take literally buckets of nesting material from these chimneys. This nesting can catch fire directly, or it can block critical air passageways between layers of metal chimney pipe, allowing the chimney to overheat. Both scenarios routinely cause house fires. Most after market chimney covers do not correctly address the problem, and can often make the situations worse. A careful screening of all potential nesting areas with the proper sized screening may be in order.

5) Finally, prefab fireplace systems eventually just plain wear out. Models go out of production and manufacturers go out of business. A factory-built unit will reach the end of is useful life when repair of the unit is no longer possible, particularly if the components that are necessary to maintain the listing are no longer available. Keep a close eye on an aging unit, and be prepared to send ole faithful to the great recycling plant in the sky before she fails completely.

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