Chapter 6: Woodstove Problems

On a cold winter day, nothing warms you the way a wood stove does. A wood stove offers an inexpensive and rewarding alternative heat source, and provides a toasty-warm place in your home, even on the coldest days.

But the hassle of an improperly-working stove will quickly seem to outweigh the benefits. Here we will discuss how to solve wood stove problems. We will cover:

• Smoky Wood Stoves
• Mechanical/Maintenance Problems
• Creosote
• Odors
• Animal Infestation

The Troubleshooting Guide section on wood stoves, page 84 contains a quick reference for stove problems and solutions. If you have a specific problem you want to address, you might start there, but you will find much more detail in this section.

The most common type of problem with wood stoves is smoke spillage. It is tempting to blame the stove design, but usually the problem is a faulty venting system or operator error. Here we will cover the different types of smoking problems, including:

• Smoky Startups
• Smoky Endings
• Constant or Erratic Smoking
• Smoking on Windy Days
• Smoking on Damp/Rainy Days
• Smoking in Other Rooms

If your wood stove smokes when you first light it, but works properly after a few minutes, here are some things to consider:

Wood Stove Dampers. Inside wood stoves or in the stove pipe, you will often (but not always) find dampers, movable metal plates that restrict the flow of smoke and gasses. When you light the stove, the damper(s) must be in the full-open position, to allow maximum draft for start-up, when the greatest concentration of smoke is produced (and the draft is weakest). If you have accidentally left a damper partly or entirely closed, the stove will smoke. If you are not sure if the damper is open or closed, figure it out before you light the fire!

The two basic types of dampers are bypass dampers and pipe dampers. Your stove may have one type, the other, both, or neither, depending on the stove design.

By-pass dampers. A by-pass damper is a moveable metal plate inside the stove, usually located at the top rear of the firebox near the flue collar. (The flue collar is the opening in the stove, usually round or oval, that the stove pipe connects to.)

If you look inside the stove, you will probably be able to see the by-pass damper (if your stove has one), although in some stove designs it is hidden.

When the by-pass damper is open, smoke and gasses by-pass the normal exit route, (hence the name), moving directly out of the stove into the stovepipe and chimney.

When the by-pass damper is closed, smoke and gasses are re-routed through a system of baffles, or a catalytic combustor, or some other type of system designed to increase the efficient combustion of the smoke and gasses.

Pipe Dampers. A pipe damper is a metal valve (essentially, a round metal plate) installed inside the stove pipe, which can be rotated by means of a handle on the outside of the pipe. Turning the handle opens or closes the plate by moving it parallel or perpendicular to the pipe (or somewhere in between).

Note: Pipe dampers are deliberately designed to allow some movement of smoke and gasses even in the full-closed position. The plates are smaller in diameter than the inside of the pipe, and usually have holes in them, allowing about 20% of the pipe opening to remain unobstructed in the full- closed position. This helps prevent smoke spillage by making it impossible to completely block the stove pipe.

The purpose of a pipe damper is to retard the flow of combustion air, smoke, and gasses in the stove by reducing the flow of smoke and gasses into the venting system.

Note: Some stoves incorporate a round or oval pipe-damper attached to the flue collar of the stove. These perform the same task as a pipe damper in the stove pipe. Most new, EPA-certified stoves are designed to be used with no pipe damper in the pipe or at the stove collar.

If your stove has either type (or both) it is essential that the damper(s) be in the open position during startup. Once the fire is established, you can regulate the burn using the damper(s).

Cold Flue at Startup. Warm air rises. Cold air sinks. So for a chimney to operate properly, the chimney flue must be warm compared to the outside air, so the smoke will rise through the chimney and exit the house. If the flue is cold at startup – and it often is, especially in chimneys built on the outside of the house rather than up the center of the house – smoke might be pushed back into the house.

Often, once the flue begins to warm up, the chimney will start to draw the smoke out. But by that time you might already have a house full of smoke.

The solution is to prime the flue before you light the fire. It's easy to do, and doesn't take more than a couple of minutes – and it can prevent you from having a bad fireplace experience. Here's how to prime the flue:

HOW TO PRIME THE FLUE: Roll up a piece of newspaper, light one end, and hold it in the firebox of the wood stove, up near the flue collar. Don't stuff it into the flue collar – you want the ashes to stay in the stove, and not clog the pipe. You might need to burn two rolls of paper. You will soon feel the draft reverse, as the warm flue gasses start to move up the flue.

Once you have primed the flue, you can light the fire.

If the newspaper trick doesn't seem to be working, try leaving the stove door open for half an hour or so, allowing heated room air to gradually reverse the flow.

Blockages. Sometimes, a smoking problem is caused by a partial or complete blockage of the flue. Creosote buildup, animal nests, leaves and debris, or internal collapse of the chimney lining or brickwork can cause blockages. If you think your chimney may be blocked, or if you haven't had it checked by a chimney professional within the past year, make an appointment for a chimney check. Your chimney professional is qualified to identify and correct chimney blockages, and to check your chimney for other hazards as well.

If your stove seems to work okay once you get it going, but smokes when you are done using it, as the fire is going out, here are some possibilities. (Note: If your stove smokes when you are deliberately operating the stove at a low-burn, see Constant or Erratic Smoking, page 63.)

Exterior Chimney. Chimneys built on the outside of the house are notorious for smoking problems when the fire is low. While chimneys built up the middle of the house have the house to keep them warm, exterior chimneys cool quickly, since they are exposed to the cold weather. So as the fire dies and less heat is emitted to keep the flue warm, the draft tends to weaken, creating the potential for smoke spillage.

But usually when a stove smokes at the tail end of the fire, a cold, exterior chimney is a contributing factor, but not the onlyfactor. Since it is generally impractical to build a new chimney inside the house (where it should have been built in the first place), first consider the other possible factors. If you can eliminate some other problems, the reduced draft that the cold chimney causes might no longer be critical.

Pay particular attention to the sections on chimney height, over-sized flue, and depressurized house.

Inadequate Chimney Height. The rule for chimney height, and the problems caused by inadequate height, are identical for stoves and fireplaces. For an explanation, see the section on inadequate chimney height in the Fireplace Problems section, page 28.

Over-Sized Flue. For wood stove venting systems, bigger is not better. An excessively-large chimney flue requires more heat to keep warm, and cools more quickly than a properly-sized flue. Lower flue gas temperatures in large flues cause reduced draft, increased creosote buildup (since the smoke tends to cool and condense in the flue), and the potential for smoking problems, especially when the fire is not burning high.

It is fairly easy to determine the minimum and maximum chimney flue sizes for a wood stove:

• Minimum Flue Size: Unless specified otherwise in the manufacturer's installation instructions for your stove, the flue must be at least as large as the flue collar on the stove. (Remember, the flue collar is the opening on the stove that the stove pipe connects to.) For example: if the flue collar diameter is 6", the cross-sectional area of the chimney flue must be at least equivalent to a 6" diameter circle.

  Note: Many flue liners are square or rectangular rather than round. While many venting experts regard round liners as superior to square or rectangular ones (due to peculiarities of air currents in vertical passageways, expansion factors, and chimney cleaning considerations), the critical factor in determining minimum flue size is the cross-sectional area of the flue, not the shape. In short, the flue size can't be smaller than the stove collar size.

• Maximum Flue Size: Current codes and standards generally recommend that the chimney flue be no larger than three times the cross-sectional area of the stove's flue collar. Anything over three times larger will very likely result in serious venting problems, not to mention potentially- disastrous chimney fires due to increased creosote buildup in the flue.

So, what size chimney flue is best?

Ideally, the chimney flue should be the same size as the stove's flue collar. Whether or not the stove can tolerate a larger flue (and how much larger) depends on the type of stove and how you use it.

Note:In any event, do not exceed the maximum flue size specified by applicable codes in your area.

Old, non-airtight stoves. Old stoves such as Franklin stoves, which offer little control to the user over burn rate, tend to vent a great deal of heat into the chimney. Therefore, a somewhat-oversized chimney may not be a problem..

Air-tight stoves. Air-tight stoves, which allow the user great control over combustion air, often vent lots of smoke into the chimney, often at relatively low temperatures. Since smoke moves more slowly and cools more quickly in these large flues, an over-sized flue can be a real problem, even if it falls within the less than three times rule. It is best to have a flue close to exactly the same size as the stove's flue collar. (And, of course, it is best to learn to operate the stove in the correct temperature range. See Tips for Woodstove Users, page 52 for details on proper stove operation.)

New, EPA-certified stoves. The new generation of EPA-certified stoves tend to vent much less smoke and much less heat into the chimney. The reduced smoke output tends to ease the problem of creosote buildup, but the reduced heat vented to the flue means less heat to keep the flue warm, and therefore less draft in a large flue.

The new stove models range in draft- sensitivity from very draft sensitive (for which even a slightly-oversized flue is a problem) to not at all draft sensitive (for which an oversized flue isn't such a problem). As a general rule, the catalytic models are a bit more draft sensitive than the non-cats, but there are many exceptions.

If you have a new, EPA-certified stove and you think your chimney flue might be too large, talk to your local stove shop to get some feedback on the track record of your particular stove model before you make a decision on changing the venting system.

The solution to smoking problems caused by an over-sized chimney flue is to re-line the flue using the correct liner size.

For an explanation of the types of liners available, see page 6. Generally, re-lining of existing chimneys is done with stainless steel or cast-in-place systems.

Depressurized House.Inadequate available air in the house can create smoking problems, especially as the fire burns low, reducing the heat vented into the chimney. This type of problem and the solutions are the same for fireplaces or wood stoves. For a full discussion, see the section on Depressurized House in the Fireplace Problems section, page 29.

Improper air space around the liner. Terra cotta liner systems incorporate an air space between the brickwork and the liner. Problems associated with an improper air space are the same to fireplaces or wood stoves. For a full discussion, see the section on Improper Air Space in the Fireplace Problems section, page 29.

If your stove seems to smoke all the time, or erratically, consider these possibilities. (Note: Smoking problems associated with wind or wet weather are covered in subsequent sections.)

Under-sized flue. Current standards require that unless specified otherwise by the manufacturer, the chimney flue should be at least as large as the flue collar of the stove. (See page 61 for more details on this requirement.)

Here's why: The stove collar on any given model of stove is sized in accordance with the stove's design. That model needsat least that much vent capacity, to vent the combustion products it emits properly and safely.

Under-sized flues lack this needed capacity, and often spill smoke into the home. Yes, some stoves function with under-sized flues without spilling smoke. But even if the stove doesn't smoke as a result, bottle-necking the smoke and gasses into an under-sized flue could create a fire hazard, and should be avoided.

Blockages.If the flue is even partially- blocked, reducing the effective venting capacity of the chimney, the stove might spill smoke. Soot and creosote buildup, animal nests, leaves and debris, or internal collapse of chimney liners or brickwork can cause blockages. If you think your chimney may be blocked, or if you haven't had it checked by a chimney professional within the past year, make an appointment for a chimney check. Your chimney professional is qualified to identify and correct chimney blockages, and to check your chimney for other hazards as well.

Multiple appliances connected to the same flue. In the past, people often connected wood stoves to flues already serving a furnace, fireplace, or other appliance. Newer standards require that the wood stove have its own, separate flue. There are several good reasons for this:

1. Soot and creosote from the wood stove could potentially block the flue, causing toxic exhaust from another appliance to enter the home.

Example: A gas-fired furnace or water heater could vent odorless, potentially- lethal carbon monoxide (CO) fumes into the house if the flue serving it is blocked.

2. The draft to one appliance can be severely affected by the other appliance.

Example: Each time the furnace cycles on, the stove might emit a large puff of smoke into the room.

3. Exhaust products, when combined, could react adversely.

Example: High concentrations of water vapor from gas-fired appliances could mix with creosote deposits, causing liquid creosote to seep into the walls of the venting system, compromising the fire safety of the chimney.

Backpuffing. Backpuffing is a specific type of smoking problem often misdiagnosed as a wind-induced problem or stove defect.

In short, backpuffing is caused by an inadequate flow of oxygen into the firebox. Instead of burning steadily, combustible gasses build up in the firebox and periodically ignite in a small explosion, forcing smoke out of the stove through every available opening, including the air intakes.

What might cause your stove to backpuff? Generally, shutting the air controls down too far, starving the fire of oxygen, AND:

• either Using super-dry wood, like pallets or kiln-dried wood blocks, which burn very rapidly, emitting too much combustible gas too quickly. (See page 53 for details.)
• or Using firewood that is split very small, which also burns too rapidly, creating an excess of combustible gas in the firebox.

Backpuffing is fairly easy to diagnose: Try opening the air control on the stove. If the smoking stops, it is very likely a backpuffing problem. Of course, you shouldn't over-fire the stove, either. If you have to open the air control to the point that the stove will overheat before the backpuffing stops, then reconsider your firewood supply. Either get a new load of properly-seasoned wood, or try mixing less- dry or larger pieces with the super-dry or small-cut pieces. (See page 52 for details on firewood selection.)

Some stoves seem to work okay except on windy days, or if the wind is coming from a specific direction. Consider the following:

Chimney is Too Short. Chimneys must meet specific requirements for height compared to the roof of the house. For a detailed explanation of the chimney height rules, see page 28. But briefly, there are two factors that relate to wind conditions.

1. If the chimney is too short compared to the roof, wind moving across the roof will either blow directly into the chimney, possibly forcing smoke into the house, or create a high-pressure system around the chimney, also causing the potential for smoke spillage.

2. If the overall height is inadequate, the chimney will be prone to spillage from wind, since a short column of hot air produces a weaker and more easily- disrupted draft, and more likelihood of draft reversal than a tall column of hot air.

Often, simply adding a few feet to the chimney will solve the problem. But consult with a chimney professional first, to determine the practicality and cost of increasing the chimney height. Your chimney professional will also check the system for other possible causes, some of which might be more critical than the chimney height.

Oversized Flue. Very large flues, which sometimes have problems even on calm days (see page 61), are often more prone to wind-induced downdrafts, since the draft is often weak to begin with. Especially when coupled with a short chimney, an oversized flue can be a serious problem on windy days.

The best solution is to re-line the flue with the correct liner size; however, if you don't have a chimney cap, and the problem is not too severe, try a cap first, in an effort to deflect some of the wind (see below).

No Chimney Cap. A chimney cap helps deflect wind. Some are specially designed as downdraft-deflectors. If you don't have a cap, get one. (See page 10 for details on regular chimney caps, and other reasons to have a cap, even if you don't have a draft problem.) While a standard chimney cap – a lid of some sort on posts or a mesh base – is not specifically designed to deflect wind, merely having that lid above the opening will help reduce some wind-related smoking problems.

But if your downdraft problem is severe, a downdraft-deflector cap might be a better option. These caps have a baffling system, generally wide bands of metal curving up over the chimney top that re- direct the wind and in some cases actually create a slight increase in chimney draft when the wind strikes the cap. Before you buy a specialized cap, have your chimney professional check the chimney to determine if your chimney will likely benefit from a special cap, and which type is best for your chimney system.

Exterior Chimney. A chimney built on the outside of the house rather than up the middle of the house is more prone to wind- induced draft problems, since the chimney itself is more vulnerable to the elements. Wind draws heat away from the chimney, reducing the temperature of the smoke and gasses in the flue, thereby reducing draft. It is generally not practical to rebuild the chimney in the center of the house. But if your chimney is an exterior one, it is even more critical that the rest of the system be correct – such as flue size, liner insulation, and chimney caps – to provide the best possible conditions in spite of the poor chimney location.

Pressure conditions in the House. Sometimes it is not the chimney that's to blame for a wind-induced smoking problem, but rather, the house. The chimney could be adequately tall, properly lined and capped, and the stove properly installed, and yet a wind-induced smoking problem could occur due to the construction of the house.

Example: Wind whipping around an unevenly-insulated home can actually draw air out of one side of the house, creating a depressurization problem inside the house (in much the same way as an exhaust fan draws air out). Depending on the location of the chimney, the house might actually pull air in through the chimney (and smoke with it) to make up for the air being sucked out by the wind.

The specific science of wind pressure is beyond the scope of this work. But the common element in wind-pressure problems is the wind-induced movement of air into and out of the house. Here's a thumbnail summary:

1. If wind factors create an area of low pressure in the room where the stove is located, then air (and smoke) may be drawn down the flue into the house to compensate.

2. If wind factors create an area of high pressure in the room where the stove is located, then the flow of smoke and gasses up the flue might actually be increased.

3. As a general rule, well-insulated homes are less prone to pressure changes inside the house from wind than poorly- insulated or unevenly-insulated homes, since less air is driven into or out of the house.

Without proper instruments and training, you won't be able to pinpoint this type of problem in your home. Your best bet is to tackle the other more obvious possibilities (above) first, such as chimney height, chimney caps, etc.

If you continue to experience wind- related problems, take note of wind direction and intensity and whether or not the stove smokes. Consult your chimney professional or a venting specialist, and discuss the possibility that the house might be the culprit.

Some stoves seem to work just fine except when it is wet out. If this seems to be the case, pay close attention to the weather when you have smoking problems. It is easy to confuse wind-related problems with rain-related problems. If it does appear to be the wetness that does it, here are some possibilities:

Cold, Wet, Exterior Chimney. If you were stuck out in the rain, cold and wet, you probably wouldn't feel particularly energetic. Well, it's the same thing for chimney draft in chimneys built on the outside of the house. Wet masonry around the flue draws heat away from the smoke and gasses in the flue, reducing the draft, and making it much harder to heat the flue in the first place.

The solution, in most cases, is relatively simple: First, install a chimney cap on the flue if you don't already have one. A cap will keep most of the water out of the flue. See page 10 for details.

Second, call your chimney professional and arrange to have a water repellent applied to the exterior brickwork, to prevent water from soaking into the chimney.

Note: See page 33 for an important note on selecting a water repellent.

No Chimney Cap. Even if the chimney is built up the center of the house, so that most of it is protected from the rain, a chimney with no cap is like an open skylight: rain will run freely down the flue, drawing heat from the smoke and gasses in the flue and reducing draft. Get a cap. (See page 10 for details.)

Warm Outside, Cold Inside. Sometimes on raw, rainy spring or fall days, it is actually warmer outside the house than inside. If this is the case, draft conditions, especially when starting the stove, will be adverse. You will probably need to spend some extra time priming the flue (see page 60), and you may need to keep a fairly brisk fire going for a while, to warm the flue properly.

If you find smoke entering a room other than the room where the stove is located, see the section on Smoking in Other Rooms in the Fireplace Problems section, page 33 for causes and solutions. (It is identical for fireplaces and wood stoves.)

Although there are countless different models of wood stoves, there are relatively few basic types of stoves, and the mechanical problems they experience are similar. (The basic types of wood stoves are discussed on page 43.) Your first step in caring for your stove is to read your owner's manual for specific information on your model of stove. If you don't have a manual, look for a label on the back of your stove that identifies the manufacturer and model, (or snap a photo of it if you can't find any label) and go to your local stove shop. You may be able to purchase a manual.

Here we will discuss some of the basic categories of problems you might experience, and what to do about them. We will cover:

• Damper malfunction
• Broken/stuck/loose handles
• Warped or broken parts
• Cracked or broken glass
• Worn or missing gaskets
• Malfunctioning catalytic combustors
• Poor performance

(See page 59 for a discussion of types of dampers.)

Bypass Damper: Handle moves, damper doesn't. If you can move the handle of your by-pass damper, but the damper is stuck open or shut, there are three possibilities:

1. Disconnected or loose damper linkage. The handle is usually connected to a bar or lever that pushes up against the damper blade when you turn the handle. (The damper blade is the metal plate that opens and closes.) Sometimes there are several components leading from the handle to the damper blade, and one might have become disconnected, or loose enough that it isn't engaging the damper blade any more.
2. Broken damper linkage component. If someone has forced the handle of a stuck damper, a part may be broken.
3. Warped, broken, or misaligned damper blade. Especially under conditions of regular over-firing or rough use of the stove, the damper blade sometimes warps, breaks, or comes out of its proper seat, so the linkage no longer engages the blade.

In any of these cases, you have two choices: hire a chimney professional to examine and repair the stove, or try to do it yourself. Some damper linkages are easily accessible, and others are nearly impossible to get at. An exploded diagram of the stove will be especially useful. Ask at your local stove shop if you don't have one in your owner's manual.

Bypass damper: Handle is stuck. If the damper handle is stuck, don't force it! You could bend or break it, creating a much bigger problem. There are three basic causes of stuck bypass dampers:

1. Damper blade is warped. If the blade is warped from over-firing of the stove, it might become stuck in place. Sometimes this happens only when the stove is cold, or only when it is hot. This is due to the expansion of the metal: In one position or the other, (hot or cold) it might hit another component of the stove, or bend out of shape enough to prevent smooth operation.
2. Linkage is broken, bent, or improperly connected. Sometimes a damaged or improperly-connected component will jamb the linkage.
3. Improperly adjusted mechanism. Some dampers have adjustable devices such as snap-locks that hold the damper in the closed or open position to help prevent accidental movement of the damper, or tabs on the back of the damper blade that engage the damper linkage. If these are too tight, the damper could be stuck open or closed.

Again, the solution is to examine the damper and linkage, and repair/adjust/or replace as needed. A properly adjusted bypass damper should operate smoothly and easily.

Pipe damper: handle moves, blade doesn't. Most pipe dampers are connected to the handle by friction: the steel rod that passes through the stovepipe has a small ridge on it that pushes up against a corresponding indent in the damper blade. A spring on the handle outside of the stove pipe puts tension on the rod, keeping the rod engaged to the blade. (Take a look at it next time you have the stovepipe off for cleaning, and you will see that it is really quite simple.)

If the ridge on the rod or the indentation in the blade becomes worn, the damper blade may begin to spin freely on the rod, so that the damper handle no longer turns the blade properly.

First remove the section of stove pipe and clean the pipe and the damper, to verify that this is the problem. Sometimes you will find that the ridge has simply slipped out, and you can push it back where it belongs. If it is worn, measure the diameter of the stove pipe, and buy a replacement damper at your local stove shop.

Pipe damper: stuck. If the damper is stuck, chances are you have a buildup of creosote and soot in the pipe. Disconnect the section of stovepipe and clean it. It is probably time for a chimney cleaning, too...

Door is too loose or too tight. Most door latches have adjustments on them. But if the door used to be okay and now seems too loose, first check the door gaskets. (See below) As gaskets become worn, the door will often feel loose. Since gaskets are the key to preventing air from leaking into the stove in the wrong place, replace them if they are worn, before you adjust the door latch.

If the door is too tight, first make sure it is properly in place and in good shape. Check the hinge pins for wear (replace them if they are worn), and carefully check to see if the door has become warped. A slightly- warped door may be okay, as long as you can properly gasket it and adjust the latch so that there are no air leaks. But if the door is badly warped or damaged, replace it.

Cracked/warped metal components. The metal plates on the inside of the stove are there to protect the outside of the stove from damage. If any of the burn plates becomes cracked or badly warped, replace it. It is a lot cheaper than replacing the whole stove down the road!

If an exterior part of the stove shows warping or cracks, you have a more serious condition. If you are up for a challenge and you have a good workshop, buy the replacement parts you need at your local stove shop, make sure you have an exploded diagram, and rebuild the stove. Be aware that it is never as easy as it looks! Those metal plates have been heated and cooled for a long time, and they won't always go back together again easily. You can also have an expert do the rebuild for you. Check at your local stove shop for details.

If the damage is severe, or if the stove is fairly old, maybe it is time to upgrade to a new, more efficient model. You will be amazed at the cleanliness, ease of use, and low wood consumption that a new stove will offer.

Cracked/broken fire bricks or refractory panels. Many stoves are lined with fire bricks or refractory panels. Minor cracks are generally no problem, as long as the bricks stay together. But if they are badly cracked and start to fall apart, it is time to replace them. Many stoves use standard fire bricks that are readily available at your local stove shop. Others have specially-designed bricks or refractory panels that may need to be ordered.

If you don't want to do the job yourself, ask your chimney professional to do the job for you.

Under normal conditions of use, the stove glass will not crack or break. Causes of glass breakage are:

1. Severe over-firing of the stove.
2. Impact (hitting the glass with a log, or slamming the door into a protruding log).
3. Spilling cold liquids on hot glass.
4. Improper glass installation.

The first three are obvious, but the fourth bears comment. In most stoves, the glass is held in place with steel clips or a cast-iron or steel frame around the glass. There is a gasket between the glass and the door, but not always between the glass and the clips or frame. If the frame is over-tightened or unevenly tightened, especially in doors that use clips, the glass could break from stress.

Picture a piece of glass held in with small metal glass clips, two of which, opposite each other, are cranked in gorilla-tight. As the temperature of the stove and metal clips increases, the clips expand, exerting pressure on two points of the glass. This is an almost sure- fire way to break the glass, and it will usually crack from one clip to the other.

So if your stove glass breaks, before you take all the pieces out, take a look at where it broke. It may offer a clue to the cause. (But first, ask if anybody slammed a log into it...)

Obviously, you need to replace cracked or broken glass. If it has been a long time since you have re-gasketted around the glass, now's a good time to do that, too.

Gaskets around doors, ash pans, air intakes, or between metal panels of a wood stove are critical to proper stove performance. Leaky or missing gaskets let air in in the wrong place, fouling the burn and often severely reducing burn efficiency.

Check the gaskets every year, and replace worn or missing ones. (See page 55 for a trick to checking door gaskets.)

Write down the model of stove you have, measure how many feet of gasket you need, and go to your local stove shop to get the supplies.

Generally, stove gaskets are cemented in place using (you guessed it) gasket cement. You will need to remove the gasket and all the old cement before you install the new gasket. Use an old screwdriver or a wire wheel on a drill to completely remove the old cement.

When the surface is completely clean, apply a thin layer of new gasket cement, and push the gasket in place. If you are re-gasketing a door, close the door to make sure the gasket is pushed in properly. If it is bunched up, the door might not close, and you don't want to find that out when it is dry!

Give the gasket a few hours to dry, and fire the stove. The cement cures with heat.

If you don't want to tackle this job, ask your chimney professional to do it for you.

If your stove has a catalytic combustor, it is critical that it be in good working condition, as the efficiency of the stove depends almost entirely on the cat.

How can you tell if the cat's working?

In general, If you have followed the instructions for lighting the stove, waited until it is up to the correct temperature, and engaged the cat, within a few minutes the stove should be burning steadily, with little or no visible smoke exiting the chimney. So go outside and check once in a while, to see how it is doing.

Some stoves have a probe thermometer mounted adjacent to the catalytic combustor that indicates its temperature. Once you have engaged the catalytic combustor, the temperature should quickly rise, often to 1200 degrees or more, although depending on the fuel you are using and how soon you engage the catalytic element, it could be lower, perhaps around 700 degrees. Check your owner's manual for the correct readings for your stove.

If the thermometer stays close to where it was before you engaged the cat, you have a problem. Either you didn't wait for the stove to reach the correct temperature for light-off to occur, or the cat isn't working.

If you don't have a catalytic thermometer on your model and you want one, you can purchase one to retrofit to your stove. These are essentially a metal probe on a wire that connects to a temperature meter. Ask about it at your local stove shop.

What do you do if the cat's not working?

Catalytic combustors are designed to last for a long time, generally five or six years, and sometimes more. How long yours will last depends on how much you use the stove and what you burn. (See page 15 for a discussion of firewood.)

First, you need to take the cat out of the stove. How to remove the cat varies. In some stove models, you simply remove a metal panel in the inside rear of the stove. In other cases you have to work a little harder. Check your owner's manual or ask at your local stove shop for specific instructions for your model.

Once you have removed it, inspect it. If the cat's peeling badly, falling apart, or otherwise obviously in bad physical shape, replace it. But if it seems to be in tact, try cleaning it, first.

How do you clean the cat?

The procedure involves washing the combustor in a hot water bath, with minimal abrasion (you don't want to scrub it, as you will remove the catalytic element from the surface of the combustor, ruining it). Check your owner's manual for specific instructions. You will find that annual cleaning is generally recommended.

If you have lost your manual, ask at your local stove shop for a guide to cleaning catalytic combustors. It is pretty much the same procedure for all stoves.

Sometimes it seems that the stove just isn't working as well as it used to. If there is no obvious problem, such as smoking, catalyst malfunction, etc., but it just doesn't seem to be doing the job it used to, consider these possibilities:

Worn/missing gaskets. Leaky stoves will often show a marked decrease in performance. See above (page 71) for a discussion of checking and replacing the gaskets.

Chimney needs cleaning. If the venting system is getting blocked with soot and creosote, it will make a world of difference in terms of performance and safety. See Checking a Chimney on page 8 for information on checking and cleaning chimneys.

Poor wood supply. Are you using the same fuel as always, or a new load? If your wood's too green or wet, it might be the culprit.

Changes in the house. Have you recently altered the house, by adding insulation, replacement windows, or new caulking? If you have made the house much less "leaky" recently, you may have a problem of depressurization. See page 29 for details.

One of the great misunderstandings in the world of woodstoves is how creosote fits into the picture. Contrary to popular belief, creosote is not an inevitable product of wood burning. Creosote forms when wood is burned incompletely, and is an indication of improper use, poor installation, or a poor wood stove design.

It is also extremely flammable, and is responsible for many chimney-related structural house fires each year.

The long and the short of it... If you find a buildup of creosote in your stove pipe or chimney, have the chimney cleaned right away, and determine what's causing it. There are four basic possibilities:

1. Operating the stove at a too-low burn rate. Especially in air-tight stoves, if you damper the stove way down, for a long, low burn, you will create a smoky fire that emits lots of unburned tar vapors into the venting system. Since the temperature of the flue gasses will already be relatively low, these vapors will be particularly likely condense inside the pipe or chimney flue.

   The solution is to keep the fire burning at a moderately-active rate. Go outside and check the flue. If lots of smoke is billowing from the chimney, you are burning it too low. Yes, this means you can't get as long a burn time from a load of wood, (unless you upgrade to a new, EPA-certified stove, which is designed to burn cleanly at a much lower burn rate) but you will actually get more heat from the same amount of wood, since creosote represents unburned fuel. You will also do your chimney and our environment a favor.
   
   

2. Using the wrong type of fuel. Burning green, wet, or excessively dry wood can cause creosote buildup. See the discussion of types of firewood on page 52 for details.
   
   

3. Oversized flue or improper connection. If the chimney isn't quickly drawing the combustion products to the outdoors, due to an oversized flue, an excessively-long stove pipe, or too many elbows in the stove pipe – all of which tend to increase the amount of time the smoke stays in the venting system – then the smoke will tend to condense in the flue, forming creosote.

   See page 61 for a discussion of correct sizing for chimney flues. And if your stove pipe is over eight feet long, or contains more than two elbows, consider re- installing the stove for a shorter run with fewer elbows.
   
   

4. Poor woodstove design. Before the new EPA-certified stoves became available, "air- tight" wood stoves were considered the best type. Airflow into an air-tight stove can be closely controlled, in some cases to the point that the user can literally put out the fire by closing the air controls.

   For a discussion of air-tight stoves, see page 44. In essence, the problem with air- tight stoves is that, while they offer the convenience of a long, low burn, they are not designed to burn the fuel efficiently during periods of low burn. Lots of fuel is wasted in the form of smoke, which condenses in the stove pipe and chimney as creosote.

   The solution is the same as for Operating the stove at a too-low burn rate, above, although many older woodstove designs create a smoky burn no matter how you operate the stove.

There are several types of odors that could detract from your enjoyment of the wood stove.

Creosote has a very strong, acrid odor, generally much worse in wet weather or in the summertime when the chimney is less effective in drawing the odor up the chimney.

The first step is to have the chimney and stove pipe cleaned. See page 8 for a discussion of checking and cleaning chimneys.

But be aware that creosote can penetrate the surface of the chimney lining, so even after the chimney is cleaned, there may be some odor. During the summer, try disconnecting the stove pipe and plugging the thimble (the hole in the chimney) with a metal cap. Measure the diameter of the thimble and buy a plug for it at your local stove shop. Sometimes blocking the hole will prevent the odors from getting into the house.

Also, if you don't have a chimney cap to keep the rain out of the flue, get one. Wet creosote smells a lot worse than dry creosote! See page 10 for details on chimney caps.

A water-repellent treatment of the exterior brickwork might also help somewhat, by keeping the chimney structure dry. Talk to your chimney professional about it, and see an important note about water repellents on page 33.

Smoke odor. If your stove spills smoke into the room, see the section on Smoky Wood Stoves starting on page 59.

If it is a lingering odor after the stove has gone out, or during the summer months, first have your chimney checked to see if it needs cleaning. (See page 8 to read about checking and cleaning chimneys.) If the chimney has been cleaned recently, consider these possibilities:

• No chimney cap. Dampness from rainwater in the chimney increases the odors emitted by soot deposits in the flue and ashes left in the stove.

  Solution: Get a cap. (See page 10 for details.)
  
  

• Soaking wet chimney. Just as a cap keeps water out of the inside of the chimney, a water repellent treatment keeps water from soaking into the outside of the chimney. And since a wet chimney smells more than a dry one, a water-repellent treatment might help. Ask your chimney professional about it, and see an important note about water repellents on page 33.
  
  

• Wind-driven downdraft in the chimney. Ideally, a chimney will draw air out of the house even when you are not using the stove, pulling odors with it. But if the odors seem to coincide with windy days, reduced draft – especially in warm weather – coupled with wind pressure may be the culprits.

  The principle is the same as for smoke entering the home during windy conditions. See the discussion on Smoking on Windy Days starting on page 65.
  
  

• Depressurized house. In some cases, air may be drawn into the house from the chimney, and odors along with it. See the discussion on Depressurized House on page 29 for details.

Burning stove paint odor. When your stove is new, or after you re-paint or polish it, there will be a period of burn-in, during which the stove will smoke and smell. Plan on burning the stove with the windows open for an hour or so after painting or polishing it.

The procedure for "seasoning" new stoves is to burn several small fires before burning a long, hot fire. During these "seasoning" fires, most of the paint burn-in will take place. But the first few times you fire the stove high, you may get some residual burn-in odor. After five or six fires, it should stop.

If you hear animals in your chimney or if you smell something coming from your chimney that you suspect is from animals (dead or alive), call your chimney professional. Don't try to remove animals from the chimney yourself. Squirrels, raccoons, and birds often nest in chimneys or accidentally fall into the flue. Since these animals carry a host of diseases ranging from histoplasmosis (a respiratory disease) to rabies, it is critically important that you avoid contact with them.

Once your chimney professional has removed the animals, have a chimney cap with a screen mesh base installed on all the chimney to prevent future animal infestation.