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Chimney Doctors Frequently Asked Questions


Fireplace with White Mantel

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When we come to clean the chimney at your home, we will need to be inside in order to have access to the fireplace. If you cannot be home at the time, you will need to make arrangements for someone to meet us there. During the colder months, we ask that you please do not have a fire in the fireplace the night before our visit, and if you have gas logs, make sure they are not turned on the day of our visit. Don't clean the ashes out of your fireplace or woodstove—this is our job.

Please move any valuable, fragile or irreplaceable items from the fireplace and hearth area. Since we have to be in and out, please secure your pets. Feel free to have your children watch and ask our experts questions about fire safety.

Payments must be made the day of service. We accept cash, checks or credit cards. If you have to cancel or reschedule your appointment, please do so as soon as possible so that your time slot can be refilled.

The N.F.P.A. (National Fire Protection Association) recommends yearly inspections to determine if your chimney needs cleaning and is safe to the current standards. Most of our customers have annual cleanings; however, some can go two or even three years between cleanings and others require two cleanings per year. Your woodburning habits will determine the frequency of chimney cleanings that you require--factors such as the type of wood you use, how long ago the wood was cut, how hot a fire you have (low, smoldering fires create more dangerous creosote), and of course how often you have a fire. It is best to play it safe and have yearly inspections to determine the condition of your chimney.

Most people think the best time to have their chimney checked and cleaned is in the early fall before the burning season. However, the best time is actually right after the burning season in the spring. You can avoid a long waiting period by calling before the fall rush. Also, if the inspection reveals a problem with your chimney, it can be repaired during the off season when we have more time to do it. By having your chimney cleaned and repaired in the spring and summer, your fireplace will be ready for you to use when the first cool spell comes in the fall.

During the hot summer months, humidity and creosote combine to cause an unpleasant sooty odor around your fireplace area. A spring service call will help to minimize this odor. Other than a sooty odor, our other major complaint from customers is birds nesting in their chimney. During the spring and summer, chimney swifts raise their young in uncapped chimneys. By having us out in the spring, we can make sure your chimney is securely capped and prevent these chimney swifts from entering the flue, becoming a nuisance and a health hazard. However, we do not remove animals, dead or alive, from chimneys. Call an animal removal service or a licensed wildlife expert if animals have made their home in your chimney. Once they have been removed, call us and we will come out and install a chimney cap to prevent any future problems.

Chimney Sweep

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It only takes a few brushes, a vacuum, and a ladder for someone to call themselves a chimney sweep. Yet it takes years of training and experience to be skilled in the trade as a true professional. In order to ensure a level of expertise within the chimney sweeping trade, the National Chimney Sweep Guild (NCSG) developed the Certified Chimney Sweep Program. Now administered through the Chimney Safety Institute of America (CSIA), the educational department of the NCSG, a certified sweep has demonstrated a knowledge of current local code requirements, the physics of burning wood and creosote formation, technical issues related to draft, chimney dynamics, and the tools and techniques of the trade. Also, a thorough knowledge of the National Fire Protection Association's code book "211--Standard for Chimneys, Fireplaces, Vents, and Solid Fuel-Burning Appliances" is a must.

Becoming certified means taking and passing an exam every three years demonstrating a knowledge and understanding of the information contained in the CSIA study manual as well as the information found in the NFPA code book 211. The study manual is revised regularly and kept up to date on new equipment, current regulations and codes, and any changes in the solid fuel industry. The exam that the certified sweep must pass is thorough, technical, and broad-based. The only legitimate certification is issued through the CSIA, and the certified chimney sweep has a badge to prove it along with the CSIA logo in all advertising.

The very fact that we have taken the time, spent the money, and devoted the energy to becoming certified means we care a great deal about giving you the very best service possible. Being certified means we have the ability to evaluate your chimney from an educated perspective as well as the ability to make sound, knowledgeable recommendations. Our certification by the CSIA is your assurance that we are committed to our business and are up to date with being the very best we can be in our industry.

Creosote is the byproduct of woodburning that accumulates in the chimney and fireplace or woodstove. It originates as condensed components in smoke (including vapors, tar, and soot). Creosote is often initially liquid, but may dry to a flaky or solid form. If left to continue to accumulate over many burning seasons, it can build up into a tar-like glaze that is virtually impossible to clean out. Creosote is highly flammable and can be ignited by a spark or the heat of a wood fire and cause a chimney fire. Chimney fires are explosive fires, hard to control, and can damage or destroy the chimney, allowing fire to spread to combustible structural materials inside the home and even spreading to the roof.

When creosote is in its early stages, it is flaky and sooty and can be removed by using professional chimney brushes as a sweep would do. However, in its tarry, gummy, or hard glazed form, it is very difficult to remove. So it is essential that a chimney be cleaned and inspected regularly to prevent creosote from building up into this flammable, hard glazed form. Another way to minimize creosote build-up is to burn only dry, seasoned wood, preferably hardwoods that have been seasoned at least 6 months to a year. Freshly cut (green) wood has a lot of moisture in it and causes creosote to build up only after a few fires. Find a dry place in which to store your wood. Also, you can minimize the formation of creosote by burning hot fires rather than low-burning, smoldering fires. Low-burning, smoldering fires create incomplete combustion--causing unburned gases from the wood to go up into the chimney, condensing on the cool walls, thereby forming creosote.

Poorly designed chimneys and improperly installed woodstoves also lead to creosote build-up, so make sure to have your chimney inspected and repaired to prevent future problems.

Split Hardwood

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The type of wood that you use in your fireplace or woodstove is not as important as how long ago it was cut. The time between the cutting of the wood and the time it is used is called the seasoning process. You want your wood to be seasoned at least 6 months to a year. Freshly cut wood (or green wood) has a higher moisture content and creates more dangerous, hard glazed creosote on the interior chimney walls. (See answer to question 4 above about creosote.) The wood that you use also needs to be dry...so locate a dry area in which to store your wood. Wet wood has a tendency to cause your fireplace to smoke.

The best and most economical time to buy your wood for winter is early in the spring so that you can get green wood and season it yourself over the spring and summer months. There is usually a considerable price difference between green and dry wood. If you do wait to buy your wood in the fall, make sure it is really dry and seasoned. Signs of seasoned wood are splits on the ends of the logs, relatively light weight, and the sound of two logs struck together (dry wood cracks, green wood thuds).

If you have a choice, the best type of wood to burn in your fireplace or woodstove is hardwood. Some examples of hardwoods are oak, hickory, dogwood, sugar or hard maple, white ash, black and yellow birch, crabapple, and apple. The reason that hardwoods are a better choice is that they are a denser, heavier wood. Denser woods have a higher heat potential (measured in BTU's). You will get more heat out of your wood for the money with the harder woods. Some examples of the softer woods which have a much lower BTU (heat potential) that you really want to avoid are box elder, cottonwood, red alder, tulip and balsam poplar, douglas fir, aspen, and pine. If you have no other choice but these softwoods, they will burn...you just will have to replenish the fire more often and will use much more of the wood in a given evening than you would the hardwoods.

Woods vary in other ways besides density, such as: ease of splitting, speed of drying, resin content, ash content, aroma, tendency to throw sparks, and coaling qualities. These are the factors that give each kind of wood its characteristics as firewood. If you are lucky enough to come across some dry, seasoned apple wood, purchase it because it has a really nice aroma when it burns. Aspen, cedar, and hemlock throw sparks. Be careful when burning these--burn only when the stove doors are closed or the firescreen is on.

No, it is not safe to use an unlined chimney or one that has a cracked liner. In order to use a fireplace for wood or gas, your chimney must be lined with no cracks or defects on the interior walls. The National Fire Protection Association (N.F.P.A.) code book on chimneys, section 7.2.2 states that all masonry chimneys shall be lined.

Under no circumstances should fires be built in fireplaces or furnaces vented to chimneys without the benefit of a properly installed flue liner. Unlined chimneys allow heat to move through brick chimney walls very quickly and can cause adjacent wood and insulation to catch fire. In addition, unlined or improperly lined chimneys venting gas or oil burning appliances can allow poisonous gases such as carbon monoxide to leak into the dwelling with possible fatal consequences.

A cracked or damaged liner is a good indication that at one time a chimney fire has occurred in the chimney. You can have a chimney fire and not even be aware that you are having one. During such a fire, the flue tile liners of a masonry chimney often crack, break, or shatter due to the intense heat. Upon post fire inspection, the chimney would certainly be labeled damaged and need to be repaired (relined) before being used again. Even though it may look innocent enough, a cracked liner can open during a subsequent fire, allowing smoke, sparks, and flames to come dangerously close, threatening the wood framing surrounding the chimney. It is essential to have your chimney thoroughly inspected and documented with the Chim-Scan closed circuit video camera by a certified chimney sweep if you suspect you have had a chimney fire.

Chimney Fire

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A chimney fire is caused by the ignition of harmful creosote deposits inside the chimney walls. (See question 4 concerning creosote.) Chimney fires require two things to occur: adequate oxygen, which is usually available, and sufficiently high temperatures. A chimney is not designed for a hostile creosote fire. It is engineered for the passage of smoke and gases and cannot handle the flames of a controlled fire for long, much less the blowtorch intensity of a 2,000 degree plus creosote fire. During such a fire, the flue tile liners of a masonry chimney often crack, break, or shatter due to the intense heat. If the fire occurs in a pre-fabricated metal chimney, there is great potential for the metal to warp and twist, forcing the joints to separate. Chimney fires generally last 10 to 30 minutes, although both shorter and longer chimney fires may occur.

Once started, there is little mistaking a chimney fire. The sound is usually often described as a jet airplane taking off--usually an extremely loud, roaring sound. This sound is caused by the very high velocity of the flue gases and of the air being sucked into the air inlet of the appliance and through leaks in the lower parts of the system. One can also hear loud popping and cracking noises during a chimney fire. If the fire is in the stovepipe connector, the stovepipe usually glows red hot and may also shake or vibrate. The most spectacular part of the system during a chimney fire is usually the top of the chimney. Very dense and dark smoke is sometimes seen, but even more impressive is the plume of flames and sparks. In chimneys without caps, the plume can be well over ten feet high. The sparks can also consist of substantial chunks of burning creosote falling to the rooftop. If the chimney fire does not spread to the entire dwelling and destroy it, what is left is a charred mess with expanded, puffed up creosote, resembling large black marshmallows.

A common misconception in woodburning is that a chimney fire burns out the creosote in a chimney, leaving it safe, sound, and ready to burn again. This is just not true. Chimneys are not built to withstand the ferocious intensity of a hostile creosote fire without serious damage and consequences.

It is critical to clean and thoroughly inspect for damage (cracks, loose brick, or warped, distorted metal) following a chimney fire. Since creosote expands during a chimney fire, the flue is left partially or totally blocked and cannot properly vent the smoke and gases from the fireplace. It is not unusual to remove from ten to thirty gallons of creosote while cleaning a chimney following a chimney fire.

Only after a certified chimney professional, using the latest equipment, has inspected and if necessary repaired the chimney, can it be safely used again. If there is damage, it should be documented with the Chim-Scan closed circuit video camera especially if the homeowner wants to have a claim processed with their homeowners insurance company.

We will only service your woodstove insert if it is properly installed and up to the current codes. If it is not, you will be charged for an inspection only and we will use our time to inspect and provide you with the estimate for the correct installation. Woodstove inserts became popular in the 1970's during the nation's first oil crisis. Homeowners were told they could just slip their woodburning insert into the fireplace and enjoy an economical way to heat their homes. However, it soon became apparent that inserts presented a unique installation and maintenance challenge. The incidence of house fires traced to the inadequate installation and maintenance of woodstove inserts escalated.

To be properly installed, a woodstove insert should have its own pipe or liner (called a direct connect) from the top of the stove all the way up the chimney. If an insert is just shoved into the firebox, the smoke chamber is way too big to properly vent the flue gases. A typical masonry chimney designed for an open fireplace has a 12 x 12 inch liner (144 square inches). The average stove insert requires an 8 inch round chimney which is about 51 square inches. If a woodstove does not have its own pipe, flue gases are allowed to linger in the flue because of an oversized chimney, thereby cooling and causing flammable creosote to condense on the smoke chamber and chimney walls. (See question 4 concerning creosote.) There are many types of tested and listed liners to take flue gases quickly and safely out of the house without allowing creosote time to cool and condense, causing a fire hazard.

Cozy Fireplace with Comfy Chair

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After the burning season in the spring, most people are concerned with having their air conditioning system serviced rather than their chimney. However, the spring is actually the best time in which to have your chimney serviced as well. (See question 2 above.) By leaving creosote, soot, and debris in the chimney over the summer months, you will more than likely experience a sooty odor once the air conditioning comes on causing a downdraft. The higher humidity of the summer months combines with the creosote in the chimney making the odor even worse. Also, if there is a leak in the chimney that never has a chance to dry out, a sooty odor will more than likely be the end result.

The first line of defense in combating this sooty odor is a thorough chimney cleaning and inspection by a certified chimney professional after the last fire of the season. Once the chimney is cleaned, make sure to keep the damper tightly closed all summer. This will prevent your flue from being the major source of "make-up air" needed to replace that drawn out of the house by venting appliances. If you do not have a damper, it is strongly recommended to have one installed. You can have one installed at the top of the chimney which tightly seals the chimney and acts as a chimney cap as well as a damper. The top damper also keeps out the rain, sleet, and snow in turn reducing the odor problem since moisture is the ingredient that releases odors from the creosote inside the chimney.

To also reduce the odor-causing moisture, we recommend an application of Chimney Saver water repellent on the exterior of the chimney as well as repairing any cracks in the crown or masonry of the chimney. Chimney Saver water repellent is the best product of its kind and should be used instead of water-proofing compounds that seal the surface. A chimney must "breathe" in order to allow water vapor to pass through. Otherwise, vapor trapped within can undergo freeze/thaw cycles that cause structural damage to the chimney.

This page lists commonly asked questions with regard to chimney cleaning, chimney repair, fireplace drafting, chimney height, smoke problems, fireplace smoke guards and other questions of interest. The solutions to these problems are covered by Chimney Doctors throughout most of Southeastern Wisconsin.