If i build a gas fireplace, will i need to build a chimney as well?
Yes you certainly do require venting to atmosphere as the fumes from the fire will build up in the room or even the house and you may not even smell the carbon monoxide as it is odorless, colorless and tasteless and very lethal / fatal after a short time. There are back vented gas fires that sit against a wall and the venting is from a rear outlet through the wall to atmosphere and the vent is waterproof and protected from heating and burning if someone accidentally touches it. There are also back sheet metal boxes that are mounted externally from the heater on the wall if you want it built into an external wall which then takes the place of a chimney and the rear of the heater sits in that and the fumes are then expelled through an external vent once again to atmosphere.
