Stop using the fireplace. If it is bringing a smokey smell into the
house, it is likely there is carbon monoxide coming in too.
Does it help if you turn off the furnace and water heater when you use
Get someone with a digital manometer to test your house pressures wiuth
your furnace and fireplace running. Get THREE carbon monoxide testers
in your house. It sounds dangerous to me. I would not try testing
this your self, you could wake up dead some morning. If your house has
a negative pressure with respect to the outside, it could be
backdrafting both the fireplace flue and the flue that serves the
furnace and water heater.