Choose the right vent to ensure the safety of your home and the efficiency of your fireplace. The type of vent that best serves your home will depend on the type of fireplace you have. The vent option for your fireplace will help you to select where to install the unit, because not every fireplace requires direct connection to a chimney. As with any major change to your home, check the local building codes for area-specific restrictions concerning the installation of a fireplace and how it must be vented.
Why Vent - Venting a fireplace accomplishes two things: bringing air into the firebox and taking exhaust away from it. Smoke, carbon monoxide and other byproducts of burning fuel escape your home through the vent, as the exhaust is warm and travels upward. The upward draft that's created pulls air to the fire from inside the heated room, aiding combustion. Without proper ventilation, the smoke would come into the room from the fireplace, bringing with it poisonous carbon monoxide gas. Even with the correct vent installed with your fireplace, you need a carbon monoxide alarm that will sound when it detects high levels of the odorless and colorless gas in the room.
Ventless - Ventless gas fireplaces are controversial when it comes to building codes. Some municipalities' building codes do not allow for their installation at all, but others restrict the installation of ventless gas fireplace units to large rooms and bar their use in in bathrooms and bedrooms, according to Carson Dunlap in "Principles of Home Inspection: Steam, Electric Wall/Floor Heating." These units operate by burning more completely, to eliminate carbon monoxide as much as possible, and they do not require exterior venting. Room oxygen fuels the fire in these units, which is why they cannot be installed in small spaces. One of the byproducts of using ventless fireplaces is the large amount of condensation they produce if the unit is not the right size for the room. Because they do not need a vent pipe, ventless fireplaces can be installed anywhere your local code allows without cutting into walls or putting the unit next to a chimney.