When those work well they're fine but be very careful. It's not uncommon of for smoke to go out what you think is the in intake and often those aren't correctly built as a chimney and so you can burn your house down.
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???