Question: hi there,i have a v.c. winterwarm,approx eight years old,i burn oak > that is usually aged two years,this year i have started experiencing > lots of backpuffing.the chimney pipe is clean,could this mean my cat > is going bad ? or what ?the backpuffing takes place mostly at > night,when we put on a log for the night and damp down the stove and > turn off the fan. > please help me out if possible,your site is outstanding...thanks jim > Answer: You actually solved the problem yourself-------------2 year old oak is "infamous" for creating the backpuffing scenario. Overly dry wood, like yours, tends to give off its smoke & gases all at once, versus gradually like wood that has more moisture. At the same time, you'll get a hot fire from this fuel which causes the WW's thermostat flap to close. So now, you have a condition where you have a firebox full of gases, and poor air flow. Eventually, you'll have air entering and mixing with the now super-heated smoke & gases--------poof You have secondary ignition taking place where only primary combustion typically occurs. Solution: Use or mix in wood that's less seasoned----wood that has more moisture. And, don't close the t-stat too much. Play around until you find the right combination, but you're wood is usually the source of aggravation. Also: Be sure that the combustor is free of ash accumulation.