I've read a risk for COPD is using a wood stove. I used one for about 10 years as a heat source, gave it up about 5 years ago. It never bothered me and my reactive airway / asthma. Never caused me to cough, benign. I have a great stove! That said, could it be like second hand smoke, in that you don't sense it but it is still there affecting you? Or maybe no one knows for sure.