Phil my biggest problem is they are in Germany & they are really hard to get hold of!
After reading many posts on this forum , I've come to the conclusion that it's either air flow due to small vents at the front of my outside smoke box or possibly because of the distance from the top of my smoker to the end of the flue approx 2-3 metres tho there seems to be a good flow of smoke coming threw the smoker!
It can't be the sawdust as the oak and beech that I have is medium grain and from reputable supply!
Something is stopping the sawdust from smouldering without the aid of the heating element
My flap/ air shutter is 25% open at the top of my smoker and 75% open on top on my outside smoke box so is this reasonable ?