Frequently Asked Questions


Q. How often should I have my chimney swept?

This a tougher question than it sounds. The simple answer is: The National Fire Protection Association Standard 211 says, "Chimneys, fireplaces, and vents shall be inspected at least once a year for soundness, freedom from deposits, and correct clearances. Cleaning, maintenance, and repairs shall be done if necessary." This is the national safety standard and is the correct way to approach the problem. It takes into account the fact that even if you don't use your chimney much, animals may build nests in the flue or there may be other types of deterioration that could make the chimney unsafe to use.

The Chimney Safety Institute of America recommends that open masonry fireplaces should be swept at 1/8" of sooty buildup, and sooner if there is any glaze present in the system. This is considered to be enough fuel buildup to cause a chimney fire capable of damaging the chimney or spreading to the home. Factory-built fireplaces should be swept when any appreciable buildup occurs. The logic is that the deposit is quite acidic and can shorten the life of the fireplace.

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Q. My fireplace stinks, especially in the summer. What can I do?

The smell is due to creosote deposits in the chimney, a natural byproduct of woodburning. The odor is usually worse in the summer when the humidity is high and the air conditioner is turned on. A good sweeping will help but usually won't solve the problem completely. There are commercial chimney deodorants that work pretty well, and many people have good results with baking soda or even kitty litter set in the fireplace. The real problem is the air being drawn down the chimney, a symptom of overall pressure problems in the house. Some make-up air should be introduced somewhere else in the house. A tight sealing, top mounted damper will also reduce this air flow coming down the chimney.

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Q. When I build a fire in my upstairs fireplace, I get smoke from the basement fireplace.

This has become quite a common problem in modern air tight houses where weather-proofing has sealed up the usual air infiltration routes. The fireplace in use exhausts household air until a negative pressure situation exists. If the house is fairly tight, the simplest route for makeup air to enter the structure is often the unused fireplace chimney. As air is drawn down this unused flue, it picks up smoke that is exiting nearby from the fireplace in use and delivers the smoke to the living area. The best solution is to provide makeup air to the house so the negative pressure problem no longer exists, thus eliminating not only the smoke problem, but also the potential for carbon monoxide to be drawn back down the furnace chimney. A secondary solution is to install a top mount damper on the fireplace that is used the least.

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Q. I heat with gas. Should this chimney be checked too?

Without a doubt! Although gas is generally a clean burning fuel, the chimney can become non-functional from bird nests or other debris blocking the flue. Modern furnaces can also cause many problems with the average flues intended to vent the older generation of furnaces.

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Q. What is level 3 creosote?

I have an 80 year old home that was a longtime rental house. I have lived here five years and have been using the fireplace for four of those years. I do not know how long it has been since my chimney was swept (potentially decades, if ever). I just had a chimney sweep at my house and he informed me that the creosote in my chimney was quite thick (he used the term "level 3" creosote). He also said that in the smoke chamber, the brick is stepped (instead of smooth) and that there is a lot of dangerous buildup in there. He recommended two applications of an acid cleaning (which he said are not entirely foolproof, and work better above 45°F) and that we use a chemical when we burn our fire to help "chalkify" the creosote buildup. He showed me the buildup inside with a light and everything he said seemed to make sense. Does this sound like it's on the up and up? I can't find any info on this acid cleaning and I would like to know if this sounds like it is the proper course of action in a case like mine.

What you have described sounds pretty typical. In addition to the chemical treatment that you mentioned, professional-grade chemicals, usually in the form of a powder, can be applied by chimney sweeps to help change the nature of the glazed creosote to a form that can be removed by a professional with a brush Both forms of these products require some heat such as you would find in a small fire in the fireplace.

If the creosote is gummy, about the only way to deal with the creosote is with a chemical treatment or with an acid application. Acid applications are not as commonly used since they are harder to apply and have to be neutralized a few days after application. If the creosote is crusty or fractures when hit (as opposed to gummy) a rotary cleaning can be helpful. Read our position statement on chemical chimney cleaning products here.

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Q. How do I know if he really cleaned my chimney?

In the past, sweeps we've hired have always gone on the roof, checked the flashing, the mortar and all the workings of the chimney and then cleaned the chimney from the top of the house. Today, this sweep came in, looked into my fireplace from the bottom and said we don't need it cleaned because he can still see the bricks. I asked to have it cleaned anyway. He then grabbed a wire brush and simply rubbed away any buildup from the main opening to the fireplace without even going up into the chimney to clean anything. Am I way off base, or did the sweep charge me without cleaning my chimney?

Your past experiences with chimney sweeps sound as though the sweep did the job he was hired to do. However, your most recent experience sounds a bit odd. If the sweep agreed to do a complete sweeping and only cleaned the brick in the fireplace firebox, you did not get the service that you paid for. A complete chimney sweeping includes the chimney flue and smoke chamber.

In the future you could ask for a Level 1 chimney inspection and a chimney sweeping. If the sweep doesn't know what a Level 1 inspection is, find one that does. A Level 1 inspection is typically required when your appliance or your venting system has not changed and you plan to use your system as you have in the past. A Level 1 inspection is recommended for a chimney under continued service, under the same conditions, and with the continued use of the same appliance. In a Level 1 inspection, your chimney service technician should examine the readily accessible portions (i.e. exposed, or easily capable of being exposed without tools) of the chimney exterior, interior and accessible portions (i.e. areas that may require the use of commonly available tools to remove doors, panels or coverings) of the appliance and the chimney connection. Your technician will be looking for the basic soundness of the chimney structure and flue as well as the basic appliance installation and connections. The technician will also verify the chimney is free of obstruction and combustible deposits.

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Q. How common is it that chimney liners cannot be seen from inside the fireplace using only a flashlight? Is there some standard building requirement for the flue and the fireplace that you can't just look up from the fireplace and see the sky or chimney cap at the top of the chimney?

Flues are allowed to have up to 30 degree offsets. In most cases this will make a direct visual observation of the flue impossible. A video scan may be required to evaluate the flue condition.

The height of the chimney flue is not a factor. There is a big difference in what is observed between a visual inspection and a video inspection, even in short flues.

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Q. Which stainless steel liners require insulation?

Liners for gas and oil-fired appliances do not require insulation to meet the manufacturers' installation and warranty requirements. Because of the lower flue gas temperatures and lesser heat transfer they are less likely to catch surrounding combustible material on fire. Those that are used with solid fuel-burning appliances do, however. If combustible materials are in contact with the chimney there are provisions that allow the liner to be installed in what is defined as a zero/zero install. That means there may be zero clearance to the interior of the chimney and zero clearance to the exterior of the chimney. The insulation may be of the blanket type or an expanded mica or masonry insulation. There are some manufacturers that will list a liner for use without insulation if it conforms to the NFPA 211 construction requirements. The problem is that it is almost impossible to determine that without destroying the chimney. It makes much more sense to insulate every liner serving a wood burning appliance. Even gas and oil-fired appliances that are vented into an exterior chimney will benefit from insulating the liner.

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Q. What is a factory-built fireplace?

Unlike traditional site-built masonry fireplaces, most factory-built fireplaces are made of metal and may use a combination of insulated walls, glass doors, air-cooled pipe and blowers to circulate the heat produced by the fire. 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, and are then are listed specifically for use with one another. In other words, a factory-built fireplace has a specific chimney that is appropriate for use with that specific fireplace.

Anatomy of a factory-built fireplace

Although models vary, factory-built fireplaces generally generate heat for the house in one of two ways. With the standard radiant heat method, the heat produced by the fire radiates from the fireplace into the room. This system is limited as to the amount of heat it will return to the house. The circulating air method uses louvers and at least one blower to force air along the hot walls, picking up heat and forcing it back into the living space.

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Q. How is a factory-built fireplace different from a traditional fireplace?

Because a factory-built unit is so much lighter than masonry fireplaces, these fireplaces do not require the concrete foundation necessary for masonry. The insulation and/or cooling spaces built into these systems allow the back of the fireplace to be placed closer to combustible materials than their masonry counterparts.

Although most units are metal, pre-manufactured, modular, masonry fireplaces are also available. These masonry models incorporate special engineering techniques that are not used in most field constructed fireplaces, including a listed venting system. Like metal factory-built fireplaces, pre-manufactured masonry fireplaces reduce the clearance to combustibles and increase the amount of heat produced by the fireplace. These advantages, coupled with the lasting nature of masonry, make pre-cast refractory fireplaces and other modular masonry fireplace systems an attractive, but somewhat more expensive, alternative to the relatively inexpensive materials and construction of the mass-produced factory-built fireplace.

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Q. What's the safest way to use a factory-built fireplace?

Proper use is critical to safe and efficient operation of factory-built fireplaces. When you light a fire, keep in mind the following considerations:

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Q. How long will a factory-built fireplace last?

Factory-built fireplaces are decorative heating appliances. They are engineered with specific components that, when properly installed, will give you years of enjoyable use. Regular service and maintenance will help owners keep a step ahead of potential problems.

A factory-built unit will reach the end of its 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.

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Q. How can I be sure the factory-built fireplace is installed correctly?

A factory-built fireplace is the only built-in home appliance which is not easily removed for inspection. It is important to take out a building permit before installing a factory built fireplace. The building inspector will conduct an examination to confirm that the system was installed according to code.

As always, reputable chimney professionals should be used when these units are purchased and installed. Local codes and the manufacturer's installation instructions should be followed to the letter.

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Q. Where can I install a factory-built fireplace?

Because metal factory-built units are relatively lightweight and do not require a footing. The reduced clearance between the fireplace and combustible materials, affords homeowners a wide range of design and placement choices.

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Q. What if the lining of my firebox is cracked?

Most factory-built fireplace manufacturers require replacement of the refractory panels of the firebox when a nickel, on end, can be inserted into the crack or when the surface of the refractory panel has abraded more than 1/4" from the original surface. Replacement of the refractory panels should be completed by a qualified professional familiar with factory-built fireplaces and the panel replacement procedures.

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Q. What does a factory-built fireplace look like?

Factory-built fireplaces are available in styles as varied as housing styles around the world.

They can be finished with practically any material, allowing many design options. A homeowner may choose to finish the area surrounding the fireplace with a traditional full-surround mantle, painted or stained, in plain design or intricate scroll-work designs. They may choose to use a simple rough-hewn mantle of cedar or they may use stonework. The front face of the fireplace can be finished with a variety of materials, including tile or marble. Most factory-built fireplaces come in a black finish, although many manufacturers offer them dressed with brass trim.

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Q. Can I have a gas log set installed in my factory built fireplace?

Yes, as long as the fireplace has a knock-out to allow the installation of a gas log lighter bar. Further, it must be listed for use with solid fuel, and the listing cannot specifically exclude the installation of gas log sets. Unless the manufacturer of the fireplace specifically allows it, the installation of "vent-free" gas log sets are NOT allowed. When allowed, the damper is blocked completely open and they are treated as a fully vented gas log set.

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All questions and answers come from the CSIA website.