Setup & Installation
- Inside Chimney vs. Outside Chimney—Does it matter?
- Stainless Steel Liners
- Supplying Outside Air to Your Wood Stove
- Chimneys & Draft
- House Pressure
Setup & Installation
Inside Chimney vs. Outside Chimney—Does it matter?
I would say it matters, “tons” which is incidentally what a masonry chimney can weigh, but I will tell you more about that later. To understand more about this subject let’s identify and define the major players in our game.
The Chimney, (Also commonly referred to as; “chimly, chimbly, chimeney or even flute.) is a vertical structure extending above the roof of a building for carrying off smoke. (Merriam-Webster)
The Stove is any manner of contraption with a load door that you can put wood in, some means of controlling combustion air, an outlet to allow smoke to escape and if you bought a Jotul it looks good even when it’s not burning.
Draft, which is a temperature difference between the inside of the chimney and the air outside which causes a pressure difference that allows the air inside the chimney to rise up and exit from the top of the chimney. (This stuff is kind of dry and there’s just no funny way to say it!)
The Inside is a place that is warm and dry and tastefully decorated and a good place to have a glass of wine with your significant other when it’s cold and raw out side.
The Outside is that cold and raw place that I was just talking about!
Since the Renaissance period when the world suddenly became a much more happy and artsy place people have been building chimneys inside the domicile. The British may not have contributed greatly to the artistic community but they knew that the chimney belonged inside the house. The Pilgrims may have endured a great deal learning how to adapt to the new world but they brought the knowledge with them that the chimney should be built in the middle of the house. Somehow this state of enlightenment has eroded and many chimneys (even as you read these words) are being built outside of the house.
So why exactly does the inside chimney function better than the outside chimney? It has a lot to do with the mysterious and wonderful force of draft. Remember in my definition I mentioned that draft was a temperature difference that causes a pressure difference. So getting back to the beautiful (looking) masonry outside chimney, we are going to have quite a challenge heating up tons of mass to create and maintain our desired temperature difference. That poor chimney is outside, where remember it is cold and raw and now we not only want it to look good but to work as well! If we are starting with a cold stove and it is 20 degrees below outside, the air inside the chimney may be 20 below too. Depending on other factors going on inside the house such as negative pressure, air may actually be coming down the chimney which is far less desirable than say Santa Claus. We might just get a house full of smoke before we get the chimney warm enough to support draft.
As a side note let’s talk a little about why an old “air tight” stove that cost $600 worked on that outside chimney and this new $2000 EPA certified stove won’t. The older stove was not very efficient and that meant that lots of the heat being produced went up the chimney. This worked very well to warm up the chimney but was also a great waste of heat. The newer EPA certified stoves are far more efficient and don’t lose nearly as much heat up the chimney. In a chimney that supports good draft and when burning good DRY hard wood you can expect to burn less wood and get more heat than you would have from the old “air tight” stove!
Now let’s move the chimney inside the house and see what happens. It all sounds so easy on paper! One thing I haven’t mentioned is that the chimney should also exit the top of the house at or as near as possible to the top of the insulated envelope. Our inside chimney is a happy chimney. The house acts like a big blanket wrapped around it to keep it warm. Now we can go back to that 20 below zero day but this time most of the air in the chimney is 70 degrees. (Or very close to the same temperature that the air in the house is.) When we start a fire in a stove that is connected to this chimney the smoke is going to go in the right direction because we already have that all important temperature difference that will support good draft! The fact is that this chimney will probably be drafting even in a static state or when there is no fire in the stove. That as they say is “a good thing”! So the moral to the story is, “If you have a choice build your chimney inside the house where it will be happy and more importantly so will you!”
Stainless Steel Liners
Some people think the only justification for lining a perfectly good chimney is that it will help line your hearth retailer’s pockets with more of your hard earned cash. After all you just plunked down somewhere between $800 and $3000 (or more) for the stove and now they are trying to get more! Please let me explain how this extra step is going to help not just you and your hearth retailer, but also your chimney sweep and maybe even the fire department. And here’s the kicker, it could even save you money in the long run.
There are five very good reasons for lining a chimney.
Creating the proper flue size.
Some chimneys are built with one purpose and then used for another at a later time. A perfect example of this is the fireplace chimney. These chimneys have large flues that are designed to evacuate the copious amounts of smoke and gases that are created by burning wood in a fireplace with a large opening. The conclusion that many people arrive at after living with this situation is they are throwing a lot of wood into a fireplace that is nice to look at but doesn’t give off much heat! The logical next step is to put a wood burning fireplace insert into the existing masonry fireplace. Here is where the liner will help. Although the chimney usually already has a terracotta liner, the size of the liner is a minimum of 8”x12” and usually 12”x12” or larger. Some would say, “ If my chimney is already lined why do I need another liner inside of it?” So here is the answer. The flue exit on most of the new E.P.A. rated wood burning inserts is 6” in diameter. When the engineers that designed these stoves were testing them they performed most of their tests on a 6” flue. And therefore it stands to reason that these puppies are going to work a whole lot better on, you guessed it a 6” flue. I have used the fireplace as an example but there are many chimneys in older homes that were built with over-sized flues that will work better if lined.
A chimney that is lined from the stove to the top is easy to keep clean.
In some cases when an insert is installed into a masonry fireplace an installer will use a “direct connect” to connect the stove to the chimney flue. In this case a short length of stainless steel flexible liner is connected to the top of the insert and run through the damper and up above the bottom of the first flue tile. The remaining damper opening is then sealed with a steel plate or ceramic fiber blanket. This installation may work fine but it creates more expense when it is time to clean the chimney. To properly clean the entire chimney in this type of installation the stove and the venting should be removed and then reinstalled after the chimney is cleaned. Chimney sweeps don’t enjoy all of this extra work and therefore charge accordingly. If an insert had been installed in this same fireplace with a full liner the chimney sweep can run his brush and rods right down to the stove. In this case the only extra step is removing the top baffle, which is very easy to do in a Jotul insert!
A lined chimney is a safer chimney.
Last night I was watching the news, which is a very rare occurrence for me. After all who really wants to hear about all of the bad things that have happened today.
Having said that I saw a report about a house that burned because of a chimney fire. Now chimney fires can start because of more than one reason. One is creosote build-up and that should not be an issue if you are burning an E.P.A. certified stove properly with “Good Wood” and “Good Draft”. Another reason is the chimney may be too close to combustible materials. A liner and in some cases an insulated liner can make a chimney much safer. Of course if you are unsure about the condition of your chimney you should always consult a professional like your hearth retailer or a chimney sweep. Now if the house in the news report had an E.P.A. certified stove connected to a properly installed liner there is a good chance that the local firemen would have been back at the station perfecting a new recipe instead of out risking their lives putting out a fire!
Some chimneys that are lined and insulated work better.
One of the best things about using a chimney liner when it’s needed is that the stove will work better. When the stove works better you will be happy, and when you are happy so will your hearth retailer. Reminds me about a saying I use often pertaining to my wife, I’m sure you’ve heard it. When Mother is happy, everybody’s happy! Some chimneys are built outside the house, which is not conducive to “Good Draft”. A large flue as I have mentioned earlier will only magnify the problem. The solution here may require adding an insulated liner, which will allow the flue to stay warmer and as a result will contribute to better draft. Another important point and an opportunity to bolster my claim that a liner may save you money can be made about improving performance and efficiency when installing a liner. If the stove is running well you will be getting more heat from the stove and get your money’s worth from your wood.
It may just be a code requirement.
This next part is pretty dry so bear with me. If the chimney is inside the building envelope and is more than three times the cross-sectional area of the flue outlet of the stove then by code it should be lined. If the chimney is outside the building envelope then it will need a liner if it is more than twice the cross-sectional area. Wow that was dry, I need a drink.
Supplying Outside Air to Your Wood Stove
I first learned about outside air kits when I was about to close a sale with a customer who lived in a mobile home. One of the more experienced salesmen in the store I had recently become the manager of, warned me that the requirements for mobile homes were different. “You need double wall connector, the stove has to be bolted to the floor, it has to be grounded to the chassis, and you need outside air.” He said. I can’t remember with absolute clarity but I’m sure I wondered why if the people in the house could breath the stove needed help. But I moved on, and in the hectic hearth store atmosphere accepted outside air as something that was necessary when installing a stove in a “tight” home. I was a little confused about fixing the stove to the floor too, did HUD think these mobile homes actually moved after they were delivered. Maybe they thought it would hold the stove in place in case a tornado came by.
Some time later outside air reared it’s now ugly head at Jotul. The more I learned about it the more I realized it was not a solution based in good science. There are a couple of schools of thought on outside air. Some think that because the air from outside is used for combustion instead of the heated indoor air there is an efficiency gain. There would be a grain of truth in this theory if there were not copious amounts of air flowing in and out of the house at infiltration and exfiltration points. If houses were truly as efficient as they are billed they would not cool down so quickly when the heat was turned off! Which leads me to the second theory. This camp thinks that some houses are so air tight that the naturally drafting stove will remove too much air from the house. If they are that tight there will be much more serious problems like mold and I don’t even want to go there. If a house is built with double vapor barriers, sealed outlets and fixtures, sealed sills, and a super insulated envelope then an air-to-air heat exchanger is a must to ensure the health of the occupants. This engineered system can be calibrated to compensate for any appliance that will remove air from the house, not just the wood stove.
An excellent source of information on the subject I found is the non-commercial web site www.woodheat.org. This is an informational site that has tons of great information for wood burners or people who want to burn wood. It was at a seminar given by one of the founders of the site that I watched a very disturbing video of “outside air gone wrong”. The video showed a zero clearance wood-burning fireplace that had an outside air “inlet” connected to it. There was a strong wind blowing and the inlet was located on the leeward or downwind side of the house. The wind was blowing across the top of the chimney creating a zone of positive pressure. There was also an area of negative pressure on the side of the house where the “inlet” terminated. Since areas of high pressure flow to areas of low pressure the combustion air was coming down the chimney and the exhaust was flowing out the “inlet”. The inlet is not designed to safely contain the heat or by-products of incomplete combustion so this installation could lead to a disastrous result.
Until we are proven wrong with science the air for a naturally vented appliance should come from the room the stove is in. Speaking of science apparently it has been applied to the notion of outside air for wood burning appliances in Canada. Research shows that the design of the stove, chimney, and house as a system has much more to do with successful venting than outside air. There are of course codes that contradict this point of view and in these cases the code should be followed in accordance with a ruling from “The Local Authority Having Jurisdiction”. Perhaps the institutions that are responsible for these codes will catch up with the times. We can only hope this will happen soon!
Chimneys & Draft
The single most important ingredient for successful wood burning in a modern, clean burning heating appliance (wood stove) is DRAFT! What is draft? Well hold on to your hat, because I’m going to tell you.
The dictionary has many different definitions, one of which is “a drawing or a pulling”. Incidentally one of my favorite definitions of draft in the dictionary is the one that refers to “a portion of beer”, but I will leave that for another, perhaps later discussion.
Draft in purely technical terms is draft is a difference in temperature between the flue gases in the chimney and the atmosphere out side the chimney that create a pressure difference”. In nature areas of high pressure flow to areas of low pressure all things being relative. We are not talking about a very strong force either. The force of good draft is so weak that it must be measured with very sensitive equipment. In scientific terms it is measured in inches of water column, or some where between .05 and .1 inches.
Before moving on let’s look back in time because as we all know, history is one of the best teachers. If we only used this historical knowledge more, life would be so much easier. In the beginning when fires were in caves everyone smelled like smoke, which was probably a blessing compared to how they might have smelled otherwise. As time passed our ancestors discovered the chimney and the best location for the chimney. Of course they knew that the best place was in the middle of the dwelling and running up through the highest point of the structure. Of course I have oversimplified this journey there was no doubt plenty of unsuccessful trial and error before arriving at this happy place.
Flash forward to the present and look at the current state of chimney location. For a few different reasons, mainly aesthetics and space concerns many of our poor chimneys have been relegated to the cold desolate outdoors. I am fond of saying, outside chimneys may look nice and act as an anchor to hold the house down during a hurricane, but the truth is that they usually don’t work very well.
So what exactly is a good chimney? A good chimney is one that removes exhaust and also draws combustion air into our clean burning heating appliance. As I have said it does this because of the force in it called draft. The funny thing is that this force should exist in the chimney even if a stove is not connected to the flue! I have witnessed the “miracle” of draft in some chimneys that was so strong, that a piece of paper placed over an open thimble, would be held in place by the flow of air up through the chimney! There are always examples of chimneys that defy logic and work when they should not. I have talked to people who own chimneys that are, 10 feet tall, originate in a basement, have 5 feet of horizontal run, 4 elbows and are outside. They swear to me that they work just fine! Don’t be fooled by these anomalies they just got lucky!
There are some constants in chimney construction and location that support good draft.
- Locate the chimney inside the insulated envelope and try to have it terminate above the highest point of the dwelling. (A warm chimney is a happy chimney!)
- Make the flue the same size as the as the outlet on the stove. (Just as water flow will slow as a river widens, draft will be weaker if the flue size is too big or be restricted if the flue is too small.)
- Use a round flue if possible. (Exhaust flow doesn’t like corners)
- Try not to introduce bends or elbows in the chimney. If you have to use elbows try not to use more than two, and if you can use 45 degree elbows instead of 90’s.
- Avoid horizontal runs if possible and if you must use them keep them short. 3 feet is an absolute maximum! (It is not natural for smoke to go sideways!)
- Make sure there are no other openings into the chimney that are diluting the draft, such as leaky clean-out doors or alternate thimbles. (This has the same effect as trying to suck soda with a cracked straw.)
- Check around the proposed termination for obstructions like overhanging branches.
- A good rule of thumb for minimum chimney height is 14 feet.
- Don’t locate a chimney in a one story addition attached two a multiple story dwelling.
- Beware of cathedral ceilings. Even if they are in the next room they might affect the performance of the chimney.
- H.V.A.C. ducts, floor vents, and cold air returns can negatively affect draft.
- Be aware of any thing that might remove air from the house like bathroom fans, kitchen range hoods,( particularly down-draft), open second floor windows, exhaust fans and open fireplace dampers to name a few.
- Make sure the chimney is cleaned regularly and don’t forget about the cap and connecter pipe.
- Start and burn your fire hot enough to help sustain good draft. (A stovetop thermometer is a must.)
There is a great web site that has much more information about draft and many other wood stove related topics. It is called woodheat.org and is a non-profit independent site. Did I mention that it is really great!
Did you even know that you house was under pressure? Do you care? Read on and you will see that Indeed it does have a profound effect on the successful operation of your stove.
So what is house pressure? Well to explain what it is we have to understand a little about relativity. Don’t worry you don’t have to be Einstein to understand relativity. First to make sure we are all on the same page we are talking about air pressure! The pressure inside the house is relative to the pressure out side the house. It may be either higher or lower than the pressure out side. If the pressure inside the house is positive or higher than the pressure out side and a window or door is opened air will leave or flow out of the house. If the pressure inside the house is negative or lower than the pressure outside the house air will flow into the house when that door or window is opened. If for some reason all of the doors and windows in the house were open equilibrium would be reached and the pressure would be the same inside and out. Nature loves balance! Seems easy enough to understand. Nature has it’s own very predictable but perhaps not very well known rules. One of them is that areas of high pressure flow to areas of low pressure. Of course when it comes to burning a wood stove in the house we will be looking at what effect house pressure has on chimneys.
Wouldn’t it be great if that was all there was to it! We could all high five and walk away. Of course as with most things in life there is a little more to it than that. In fact in most houses there is an area of negative pressure, an area of positive pressure and a magical place in between called the Neutral Pressure Plane (NPP). The NPP is the place where the pressure inside the house is equal to the pressure outside the house. They are all in a state of flux, changing quite literally with the wind and many other factors. The negative pressure area is typically located in the lower portion of the house and positive area is normally in the upper portion. The NPP as I have mentioned is between them. The NPP is often depicted as a straight line but it can actually be slanted or wavy and can jump around from level to level.
So lets apply some of what we are talking about to wood stoves and chimneys. There are two openings in our system, the door or the air control on the inside of the house and the chimney termination on the outside. If we put our system in an area of negative pressure the chimney, which is a conduit that air or flue gasses can flow through, might like an open door or window, allow air to flow into the house, especially if it is an outside chimney. If we locate the system in an area of positive pressure the air should flow out of the house.
Now lets add some variables that can sabotage our system. Anything that will take air out of the house mechanically like, but not limited to down draft ranges, bathroom exhaust fans, dryers, whole house fans, shop exhaust fans and range hoods can create negative pressure. Recessed lighting is another culprit. If not sealed properly they are like holes in the ceiling that air will flow through and raise the NPP creating a greater area of negative pressure. A masonry fireplace with an open damper may be taking air out of the house and creating negative pressure. Some people sleep with a window open on the second floor and that can raise the NPP. There are other culprits but I think you get the picture.
So what is the solution to stopping all of these forces that are trying to get between us, and a nice warm fire in the woodstove? The best possible solution is to locate the chimney inside the house and have it run up through the highest point in the insulated envelope. The opposite of this is a chimney that is located outside, which is almost certainly doomed to fail. If the chimney is inside the house and terminates through the highest point of the roof we achieve many desirable results. First and foremost we keep the chimney warm. A warm chimney is a happy chimney! This is because a good chimney produces draft and draft is a temperature difference that produces a pressure difference that pulls air or flue gasses up the chimney. It is much easier to keep a chimney warm when it is located inside the house. Just think of what the temperature difference would be when it is 70 degrees inside and below freezing outside. Because the warm happy chimney is producing strong draft it will be able to compete with all of the other forces that are trying to keep it from doing its job. Remember that pesky little NPP I was talking about? Well the chimney if located inside the house will have one that is higher than the NPP in the house and the result will be a chimney that has draft even when the stove is not running! As Louis Armstrong would sing, “What a wonderful world”. Lets not forget the best part, with all the cards in our favor the wood stove will be responsive to control and provide sought-after heat.
Good Stove Wood
There are many different factors that affect the outcome of successful wood burning. Many will argue as to which one is most important but instead of arguing let’s just start with wood!
If a tree falls in the woods, and there is no one there to hear it, does it still make a sound? Well if nobody told you yet, yes it does make a sound. The real news is that when a tree falls it begins to decay and releases Carbon Dioxide. Coincidently the very same release of CO2 occurs when we burn wood! In the greater scheme of things the effect on the atmosphere is virtually the same. Why does this matter to us? Because unlike when fossil fuels are burned releasing otherwise trapped CO2 into the atmosphere, when we burn wood we are NOT adding to the Green House affect! Now I don’t know about you, but knowing that, is making me feel all warm and fuzzy.
We see trees as a renewable source of energy that when cut, split and dried under cover will provide heat. In a word wood is “FUEL”! The question we have to ask our-selves is what type of wood makes the best fuel to burn in our modern EPA rated wood burning appliances? And the answer is “It depends”.
In the Northeast almost everyone (not quite every one, believe me I’ve talked to a few) knows that good dry hard wood like oak, beech, maple, ash and birch are best. However in some areas like the Rocky Mountains soft wood is plentiful and hard wood is almost nonexistent. Can you burn dry soft wood? You bet! You just can’t achieve the long burn times printed on those darn brochures with dry soft wood. The main difference between dry hard wood like beech and dry soft wood like quaking aspen (why is it so scared we’re just going to cut it down and burn it) is density. Beech is more dense (no that doesn’t mean the aspen is smarter) so there is more weight in the same amount of volume. So on a larger scale there is more heat value or BTU’s in a cord (4’x4’x8’ or 128 cubic feet) of beech than there are in a cord of quaking aspen. In plain English a cord of beech will burn longer and give off more heat (In the same appliance, chimney, house, etc.) than the cord of aspen.
Has any one picked up on the fact that I keep using the word DRY in front of wood? We have all heard it and said it but what does it mean? Is finding dry wood like finding the Holy Grail? During certain times of the year it can be. Dry wood does not come from a place advertised in a newspaper in October. Dry wood does not happen at the speed of e-mail or cell phones. Dry wood is the result of a long and deliberate process that involves planning and dare I say thought. They say that good things are worth waiting for and if you have ever tried to coax heat from wet wood you will agree.
Let’s attack this subject from a different angle and talk about “wet wood” or as some call it “green wood”. As an old Vermonter once told me the same thing that makes wood wet makes maple trees so popular in the springtime. The stuff coming out of those taps and dripping in to those buckets, you know, sap. They pour all that sap into great cauldrons and build blazing fires under them (with good dry hard wood). The sap bubbles and boils and gives off great clouds of steam but at no time has the sap ever burst into flames…because IT’S WATER! And as we all know water does not burn, as a matter of fact ask any fireman it’s what they use to put out fires! In scientific terms moisture content in wet or green wood can be 50% or more! That would mean that a log weighing 4 pounds would have 2 pounds of water in it. Even so called, dry wood has about 20% moisture content but for our purposes that is just fine.
So how do we obtain this elusive prize? It’s quite easy actually if we plan ahead and use our heads. Depending on the species, wood should be cut, split and allowed to dry under cover from 6 months to 2 years. The woodpile should be elevated off the ground, with pallets or some other method and be covered on top but left open on the sides. It is important that the wood is protected from rainfall, but is allowed to be gently caressed by the warm summer wind. Another good idea is to get the woodpile out in to the open as much as possible. There is nothing quite as powerful as the sun when it comes to properly seasoning wood. Sounds crazy I know but your wood will thank you the following winter by providing you with plenty of nice heat.
One other important tip is log length. If you have a stove that will accept a 22” log and you have your wood cut to 16” length you are leaving part of your “tank” empty. Have your wood cut 2” shorter than your firebox dimension and then if there is a little variation in actual length the logs will still fit.
My final point is about timing. The right time to buy wood is well before it is going to be burned. A nice bonus as well is that the cost can be considerably less for green wood. Remember depending on the species the seasoning time can be as long as 2 years.
Starting a Good Fire in Your New Wood Stove
Anybody can start a fire right? What could be easier Get some wood and some matches and away you go. Pretty soon you’ll be making goo goo eyes at someone in the warm glow provided by the crackling fire. Or maybe not, you might be wondering where the romance went as you try to get all the smoke out of your house. Some people start their fires with what I like to call the Manhattan start up, three pieces of wood and one page from the Wall Street Journal. Although this might be a good way to make smoke I can share a better way to build a FIRE!
To start a fire you should have at least six things:
Draft is a force in your chimney that is the result of a temperature difference between the air inside the chimney and the air outside that causes a pressure difference. This pressure difference causes the air inside the chimney to rise up and exit from the top of the chimney. To learn more about draft see my article called “Good Draft”.
Tinder is any dry combustible substance such as newspaper or wood shavings that will catch fire when you touch them with a lit match or lighter.
Kindling is wood that is very dry and split into pieces that are no bigger than 1 inch by 1 inch.
Dry wood is wood that has been stacked, split and allowed to dry under cover until it reaches 20% moisture content. To learn more about dry wood see my article called “Good Wood”.
Matches or a lighter
…need I say more?
Stove top thermometer
A thermometer is like a speedometer, it will tell you if you are burning hot enough or too hot.
Now we are ready to start a fire! Like anything else in life starting a fire will be much easier and be more successful if we build a good foundation. I use plenty of newspaper. I ball it up and cover the entire base of the stove. I have been known to use the entire newspaper! (Not the Sunday edition of the New York Times) Then I use plenty of kindling. I lay down three or four layers of kindling in opposing directions so air can circulate through the layers. At this point I add a few small logs, because by this time there isn’t much room to put in much more. To add a little insurance I crumple up two or three more balls of newspaper and cram them in on top of the logs. I am assuming for this example that draft is present. With my match or lighter I light the paper on top first and then light across the bottom. Now I can set the air control wide open and close the load door. An important point is that you should NEVER open your ash pan door to get the fire going. This can damage the stove and greatly reduce the useful life of the stove. I leave the air control wide open until my thermometer reaches 400 degrees. The fire will burn robustly and do a great job of warming up the chimney and establishing a strong draft. At this point the kindling has probably burned down enough so I can add more wood. When this additional load has caught and I am still seeing a surface temperature of at least 400 degrees I can now turn the air control down for an extended burn.
Breaking in a New Wood Stove
A series of three break-in fires are required. The first is to raise the surface temperature of the stove to 200 degrees. Another is to raise the surface temperature to 300 degrees. And yet another is to raise the surface temperature to 400 degrees. A stove top thermometer is required for this procedure and the stove should be allowed to cool to room temperature between fires. Note: Use less wood. You can always add more. All current Jøtul wood-burning appliances are EPA certified and non-catalytic. EPA certified wood-burning appliances are not "airtight." Therefore, exact temperatures may not be able to be maintained. These temperatures are ideal and should be used as a guide for proper appliance break-in. Credit: Jotul Stoves
Curing the Paint
On initial firings, the exterior of the stove will smoke. This is normal and will happen with greater intensity on a painted stove. It will subside after the first few fires. You may have to open a door or window near the stove.