It could be an out air intake. Fireplace suck air. If there isn't a vent ducting outside sir directly to the fireplace, it will pull it through anywhere it can that cold air then mixes with the warm air in the house..
It could be an out air intake. Fireplace suck air. If there isn't a vent ducting outside sir directly to the fireplace, it will pull it through anywhere it can that cold air then mixes with the warm air in the house..
Hmm TY