As far as health issues it would seem you would need to be standing outside the building to be worried about them. The flame is vented directly to the outside via the chimney and the heat is transferred indirectly via the heat exchanger. Nothing about the flame or fumes should be open to the inside of the building. At least that is the way I see it, but I do not own one so do not know for sure. They appear to me to work the same way as the heat exchanger on a vented propane stove.

John