Owners must learn and practise the skills needed to operate their wood-burning system effectively. By mastering the techniques offered here, you will

• reduce the amount of wood you need to burn to heat your home;
• reduce outdoor and indoor air pollution from wood smoke;
• reduce the frequency of chimney cleaning; and
• increase the convenience and pleasure of wood burning.

The Basics: What Happens When Wood Burns

As firewood burns, it goes through three phases.

Boiling off the water – Up to half the weight of a freshly cut log is water. After proper seasoning, the water content is reduced to about 20 percent. As the wood is heated in the firebox, this water boils off, consuming heat energy in the process. The wetter the wood, the more heat energy is used to boil the water. That is why wet firewood hisses and sizzles and is hard to burn, while seasoned wood ignites and burns easily.

The emission of smoke – As the wood heats up and passes the boiling point of water, it starts to smoke. The smoke is the visible result of the solid wood decomposing as it vaporizes into a cloud of combustible gases and tars. If the temperature is high enough and oxygen is present, the smoke will burn. When it does, it produces the bright flames that are characteristic of wood combustion. If the smoke doesn't burn in the firebox, it exits the appliance into the flue pipe and chimney. Here it either condenses – forming creosote deposits – or is expelled as air pollution. Unburned smoke also represents a less efficient appliance because smoke contains much of the wood's total energy. Advanced combustion systems are designed to burn the smoke before it leaves the stove, which is one reason they are more efficient than older models.

The charcoal phase – After the water has boiled off and most of the gases and tars have vaporized out of the wood, charcoal remains. Charcoal is almost 100-percent carbon. It burns with a red glow and some flame or smoke when enough oxygen is present. Charcoal is a good fuel that burns easily. However, burning charcoal often produces carbon monoxide, a serious indoor air pollutant.

Phase 1 Evaporation of water	Phase 2 Emission of smoke	Phase 3 Charcoal

In practice, all three phases of wood combustion usually occur at the same time. The wood gases can flame and the edges of the pieces can glow red as charcoal burns, while water in the core of the piece is still evaporating. The challenge in burning wood effectively is to boil off the water in the wood quickly, while making sure the smoke burns with bright flames before it leaves the firebox.

With the new, advanced combustion designs, two flame zones are often visible: the primary flame that rises from the wood and the transparent secondary flame that swirls above the wood. Once a good fire is established and you turn down the air control, you can see the primary flames slow down and become smaller. To get a clean, efficient burn, make sure that there is always a secondary flame. A welcome feature of these advanced wood-burning designs is that the better the combustion and the cleaner the burn, the more interesting the flame looks.

Starting a Fire

You need the following ingredients to build and maintain a good wood fire:

• a properly designed and installed wood-burning system;
• newspapers (do not use coloured or coated paper);
• dry, finely split kindling in a variety of sizes; and
• dry cord firewood split into a range of sizes.

To Build a Kindling Fire – Use plenty of crumpled newspaper and dry, finely split kindling. Never use glossy paper or coloured advertising flyers. Open the air control fully. Light the newspaper near where the combustion air enters the firebox. When a kindling fire is built properly, you should expect rapid ignition with no smouldering. Never use liquids to start a fire.

The first step in building a fire is to find out where the combustion air enters the firebox. In most advanced stoves and fireplaces, some air enters the firebox through a narrow strip above and behind the glass panel. This air wash flows down across the glass to the front of the fire. (It flows downward because it is cooler and heavier than the combustion gases.) Most models also have the primary air inlet near the bottom front of the firebox, usually just inside and below the loading door. This is where you light the fire, so that it gets plenty of air.

Next, crumple four or five sheets of newspaper and put them in the firebox. You may need more newspaper if your firebox is large or your kindling isn't dry or finely split. Many people make the mistake of using too little newspaper – be generous and you will have more success.

Hold the paper down with 10 to 15 pieces of dry kindling. Softwoods, such as cedar and pine, make good kindling (of course, use the species available in your region). Place the kindling on and behind the newspaper, so that the combustion air reaches the newspaper first where you light it. It is also a good idea to add one or two small pieces of dry firewood to the kindling load before lighting.

Open the air control fully, light the newspaper and close (but don't latch) the door. When the paper is flaming brightly and the kindling catches, latch the door. Some appliances have more restrictive air supplies than others, so you may have to leave the door ajar for as long as 15 minutes – until there is a hot kindling fire and the chimney is producing strong draft. Since leaving the door unlatched or open even slightly for extended periods may cause dangerously high temperatures, NEVER leave the stove unattended in this condition.

When starting a wood fire, your goal is to light it once and make sure the fuel ignites rapidly. Practise this procedure a few times – you might be surprised at how quickly you can establish a hot, bright fire. When the flames from the kindling load begin to subside, gradually add several small pieces of wood. Avoid smothering the fire with the new wood. Place the pieces on and behind the burning kindling.

Note The suggestions offered here are general and apply to many wood-burning appliances. However, some combustion designs – notably some of the new advanced combustion stoves, catalytic systems and masonry heaters – may require special firing techniques. In this case, you should follow any detailed firing instructions in the operator's manual that came with your stove or fireplace.

An Alternative – Building a Top-Down Fire

You may find it convenient to build a wood fire using the top-down method. To build a top-down fire, reverse the procedure described in the "Starting a Fire" section above – that is, place two or three firewood pieces at the back of the firebox and lean 10 to 15 pieces of kindling against the logs. Then place several crumpled sheets of newspaper on and around the kindling. Open the air control fully, light the newspaper and close the loading door. The fire will start reliably and progress to the large pieces of wood without any further poking or adjustment.

There are several advantages to the top-down fire building method:

• there is less visible start-up smoke at the top of the chimney;
• there is little chance that the fire will collapse and smother itself; and
• you do not need to open the loading door to add larger pieces once you establish the kindling fire.

The top-down fire technique isn't appropriate for every type of wood-burning appliance, but it can be effective in some cases.

To Rekindle a Fire from Hot Coals – Rake the charcoal toward the front of the stove where the combustion air enters. Place the pieces of wood on and behind the coals. Open the air inlet fully and leave it open until the wood pieces are well charred. This illustration shows how pieces are arranged for an extended fire.

Rekindling a Fire from Charcoal

In many wood-burning stoves and fireplaces, there will be live coals toward the back of the firebox, furthest from the air supply, after the fire has burned down. To rekindle them, first remove the ashes from the front of the firebox, then rake the live coals forward until they are just inside the loading door. If only a small amount of charcoal remains, you will have to start with kindling. If you have a good quantity of glowing charcoal to work with, place the new load of firewood on and behind the charcoal. Open the air inlets fully and close the door.

With some of the new, high- efficiency combustion stoves, you have to alter the procedure slightly. Read the manufacturer's instructions and experiment a little. For example, some designs require you to make a channel through the ash pit from front to back, underneath the wood.

Once you have added new wood to the charcoal, expect it to ignite almost instantly. The bottom pieces may even start flaming before you get the door closed. Allow the fire to burn with bright, turbulent flames until the wood is charred. This usually takes between 10 and 20 minutes, depending on the size of the pieces and the moisture content of the wood.

When the wood is charred, gradually reduce the air setting to produce the amount of heat and length of burn you desire. You may want to try reducing the air control setting in two or three stages. The result will be less smoke because the fire won't have to recover from a single, large reduction in air supply.

Remember the most important rule: Never let the fire smoulder. As long as there is solid wood in the firebox, there should be active flames. Without flames, smoke will escape unburned, reducing efficiency and increasing pollution. With advanced systems, you can achieve a reliable overnight burn while maintaining flaming combustion and still have enough charcoal in the morning to kindle a new fire.

Other Useful Tips

Arranging the Firewood – Small pieces of firewood arranged loosely in a crisscross pattern burn quickly because the combustion air can reach all of the pieces at once. Larger pieces in a compact pile burn more slowly because there are fewer spaces for the air to penetrate the load. Try to add more than one piece of wood to a fire – you need three or more pieces to form a sheltered pocket of glowing coals that reflect heat toward each other and sustain the fire.

A small, loosely stacked fuel load is good for short-duration flash fires.	A compact fuel load is good for extended firing cycles.

Firing in Cycles – Don't expect the fire to provide perfectly steady heat output. A wood fire burns best in cycles. A cycle starts when a new load of wood ignites from a charcoal bed and ends when that load is consumed and becomes another bed. Each cycle provides three to eight hours of heating, depending on how much wood you use, how much heat you need and how large your firebox is. Plan the firing cycles around your household routine. Be cautious about leaving the stove unattended when you are away.

Loading for a Flash Fire – Use a few small pieces of wood for short fires to "take the chill off." Load the wood loosely in a crisscross arrangement. Let the fire burn brightly until most of the solid wood is burned, then reduce the air setting. Flash fires are effective in spring and fall when the heating load is modest. By using the flash fire technique, you avoid smouldering fires.

Using a Flash Fire – A flash fire is a small amount of wood burned quickly. Use it in spring and fall when you just want to take the chill off the house. The flash fire technique eliminates the smouldering fires that are common in the spring and fall. To build a flash fire, rake the charcoal toward the air inlets and place several small pieces of wood on and behind it. Stack the pieces loosely in a crisscross arrangement. Open the air inlet to produce a hot, bright fire. You may reduce the air supply slightly as the fire progresses, but never enough to extinguish the flames.

Extending a Fire – To achieve a longer-lasting fire – to heat the house overnight or while you are away – rake the coals toward the air inlet and use larger pieces of wood placed compactly in the firebox. Placing the pieces close together prevents the heat and flame from penetrating the load and saves the buried pieces for later in the burn cycle. Open the air inlets fully for five to 20 minutes, depending on load size and fuel moisture content. When the outer pieces have a thick layer of charcoal, reduce the air control in stages to the desired level.

Removing Ashes – Some advanced combustion stoves have ash pans as standard equipment or as an option. Some use a simple grate through which ashes drop into the pan. Others have a plug in the stove floor that, when lifted, allows ashes to fall into the pan. Make sure that the ash door is well closed and sealed. If your stove doesn't have an ash pan, ask your local retailer for an ash handler into which you can scoop ashes through the loading door.

The ashes may contain live coals that can stay hot for days. If you don't dispose of them carefully, they can pose a fire hazard. Place ashes in their own metal container and keep that container on a non-combustible floor, preferably outside the house. Special double-bottom ash containers – with tight-fitting lids designed to hold ashes until they are cool – are available in stove and fireplace stores.

Using a Thermometer – A thermometer helps you use your wood burner more effectively, particularly if you can't view the fire through glass doors. There are two types of thermometers. One has a probe that you put into the flue gas stream through a small hole in the flue pipe. The second is a magnetic thermometer that sticks to the outside of the flue pipe or stove top.

Install the probe-type thermometer in the flue pipe about 50 cm (20 in.) downstream from the exit of the appliance – but never on the appliance. The stack thermometer tells you how hot the flue gases are.

The magnetic thermometer, on the other hand, measures the temperature of the flue pipe, so its temperature will be lower than the probe thermometer's.

Some manufacturers recommend the use of a stove-top thermometer, rather than a stack thermometer. It works the same way, but the temperature range will be different since it measures the surface temperature of the stove.

When you fire the stove at a high temperature to drive moisture out of the fuel, use a thermometer to tell you when you can reduce the air supply. Every wood-heating system behaves differently and thermometers vary, so there are no exact temperatures that you can follow. However, to avoid damaging the stove's internal parts, don't let the flue gas temperature rise above 460°C (860°F) on a stack temperature probe for more than a few minutes. Learn which burning connections result in the stack temperature you measure. With experience, you will be able to tell by the thermometer if you have set the air control too low and when you should reload.

Advanced combustion wood stoves do not need thermometers as much as older equipment does. You can check the condition of the fire visually. If the fire is burning properly, the glass door stays clear. If the glass becomes hazy or develops dark stains quickly, the fire has been turned down too low or the firewood is too wet. The glass should stay clear when the fire has a higher heat output and the firewood is of good quality. Another indicator is the flame itself. The more complex the flame, the better the combustion in the stove.

The Efficient Wood Fire in an Advanced Stove

When you master the techniques for efficient wood burning, here is what you should see.

• When wood burns, it flames until only charcoal remains. (If there are no flames, something is wrong.)
• If there are firebricks in the firebox, they will be tan, never black.
• Steel or cast-iron parts in the firebox will be light to dark brown, never black or shiny.
• If the wood is seasoned and well split, the air settings are correct and the load is arranged properly, a new load of wood will ignite rapidly from the charcoal – some pieces will be flaming before the door is closed. If the appliance has a glass door with an air wash, it will be clear. If the appliance has a glass door without an air wash, it will be hazy, but it should never be black.
• The exhaust from the top of the chimney will be clear or, in winter, white with steam. A plume of blue or grey smoke indicates smouldering and poor combustion.