Gugi47, I burn almost all ash in my owb. It does ash over during idle time but when it calls for heat my air blower gets it going good again. It also coals up quite abit to but that is normal with any wood in an owb. I have to stir it up and pull coals to the front and let the air blower burn it up or it will just pile up. Now an older owb without baffles or a smoke bypass will not ash up as most of the ash gets blown right out the short chimney. I added 6' to my chimney and have really noticed that the coals build up now, I blame it on not as much fine ash going out the short chimney when the air blower kicks on. In the old days on still snowy mornings you could see the grey ash on the snow and sparks coming out the short chimney.