Secondary combustion: what is it?
When lighting the stove, the main combustion chamber will first generate an incomplete combustion and will smoke. After a few minutes, the air between the 2 walls of the stove will heat up and as it leaves the holes at the top of the chimney, will begin secondary combustion. You will then see flames at the top of the stove. This secondary combustion will reduce the amount of smoke and enable an almost complete combustion of the wood.