If there's smoke,is it AUF or AOF to blame?

[Bruce L]

Once in a while I notice whisps of smoke where the arch exhausts into the chimney,should I be looking at the air under the grates,or air over the fire to increase to nullify this?

[RileySugarbush]

I'd guess that the total air flow is a bit too much for your stack. Pushing too much air in without a big enough draw results in positive pressure and that is likely what is pushing a little smoke out. Try cutting back on the air, I'd cut AUF first, or add a bit of stack height and see how that works.

[802maple]

Actually it is the lack of air that is doing this, mostly due to aof, unlike typical woodfired arches, you want positive pressure. Do not push to much under the fire because this will push heat up the stack.