Eco-friendly combustion with correct air supply

Air supply is one of the most important factors when it comes to firing in a correct and eco-friendly way. Therefore it's good to know a little about using your wood burning stove's air inlet controls correctly - this way you'll get optimal and complete combustion.

Author: Line Nederby
Published: 18. November 2015


About air supply when lighting a fire

– and why it’s important

It’s important that there is plenty of air when lighting a fire. Air is necessary for a clean and complete combustion process where the temperature is high enough to burn the particles and gases which the firewood releases.

If the gases and the particles aren’t burnt, it’ll turn into soot in the flue or it’ll show as dark smoke emanating from the chimney. That’s why it’s a good idea to check to see that the smoke rising from your chimney is either white or see-through when you light a fire in your wood burning stove.

Read more about chimneys here

How to use the air inlet controls 

When you light a fire in your wood burning stove, it’s useful to know the three phases of combustion – and how and when to supply air.

Most stoves have a primary and a secondary air inlet control. The primary air inlet is situated near the ash pan and the secondary air inlet near the top of the wood burning stove. Those are the two inlets you need to regulate manually during combustion. The primary air inlet is used in the beginning to get the fire going while the secondary air inlet is used to keep the fire going.

Tertiary air is a constant stream of air which ensures that smoke gases are burnt. This is regulated automatically and can be found in the back of the fire box in newer wood burning stoves.

The firing phase

In the firing phase, you should open the primary and secondary air inlet controls and you can also leave the door slightly ajar. You need plenty of air to get the temperature to rise as quickly as possible.

When the first fire has burnt and there are only embers left, you’re ready for the first firing. Read the guide here:

The first phase of combustion

In the firing face, you have to open up the primary and secondary air inlet controls completely. After this, you should put dry firewood in the stove. You need plenty of air to get the temperature to rise as quickly as possible.

The middle phase of combustion

When the fire is burning brightly (after about 2-5 minutes), you need to adjust the primary air inlet control so it doesn’t let in too much air – this is to avoid that the firewood burns too quickly.

The fire still needs the secondary air inlet control in order to keep the high temperature which ensures that the gases from the wood are burnt. The secondary air inlet control can be adjusted so it’ll fit your needs, but you should keep in mind that the air supply shouldn’t be reduced so much that the flames aren’t bright anymore.

The last phase of combustion 

When the flames die out and only embers are left in the fire box, you should put more firewood in the stove. You’ll need to open up for the primary air inlet control again, put firewood in the stove and start over again with the combustion process.  

The instructions for your wood burning stove are helpful   

All wood burning stove’s are different. When you buy a new wood burning stove, it’s going to take time before you have got to know it and have learnt how to fire optimally and obtain a good combustion process.

If you still have the instructions for your wood burning stove, it might be a good idea to read them so you’ll get precise information on how to use the air inlet controls correctly.

Reduce the amount of firewood – not the air supply 

Many people make the mistake of reducing the air supply because they wish to “turn down the heat” or make the firewood last longer. Old wood burning stoves without tertiary air in the back are sensitive to reduced air supply. New eco-labelled stoves are designed to burn cleanly with a somewhat reduced air supply. Wood burning stoves which carry the Nordic eco-label can be adjusted so you can control the wood burning stove’s effect to a certain degree – but the amout of firewod that you use and the intervals between firing are often the best way to regulate the heat.

If you reduce the air supply too much, you’re also reducing the quality of combustion and increasing the amount of particles released – which you must avoid.

Did you know that some modern wood burning stoves have an automatic control device? It’s easy for you and you’re ensured eco-friendly combustion


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