Hi, we have a very lovely fireplace in our house going to waste in this cold weather, I really want to restore it, but every time we light it, it works fine until its about to go out and then all the smoke comes inside, setting off fire alarms, and resulting in us having to open windows and doors. Slightly defeats the object of having a fire to heat up house. We've had it cleaned but the chimney sweep didn't seem to know why the smoke was coming inside the house, as it did the same thing after we had it cleaned. Can anyone help? Its a wood fire place, house was built in late 60's i think. Thank you.