[dylan604]

Knowing how ours were built, I don't even know what you describe could happen. The intake vents are on the floor with a standard height raised hearth (12"???) while the exit vents are about 6' off the floor. Not really sure how smoke is any where near the intake. The smoke is contained within the chimney. I'm at a loss at how to design something so poorly that the smoke is near any vents. Then again, I've grown up around construction, so maybe that knowledge is preventing me from thinking dumb???

[bluGill]

Maybe I misunderstand your description. I'm referring to the fresh air inlet for the fire, not additional HVAC pipes. It is common for attempts to put a fresh air inlet in a fireplace to instead have smoke go out that fresh air inlet.