The gas fireplaces can have a couple of different venting options. One of the options to the gas fireplace vent is the B-vent of the Natural vent.

 This option uses the air in the room for the combustion process. The air is sucked in from the front of the unit and is then removed through venting that terminates above the roof line like a furnace. While this is a more decorative it does lower efficiencies. This option does cost less then the gas fireplace direct vent system.

The ventless gas fireplaces system operates without the use of vent, chimney or even a flue. This will allow for the gas fireplaces to be installed almost anyplace that the gas lines can be ran. These fireplaces are inexpensive and have low operating costs. Most of these units will operate during power outages. The air is drawn in from the room, used in the combustion and then returned to the same room. While some of the major manufactures will not produce these units, they are equipped with the Oxygen Depletion System, commonly referred to as the ODS. This system will shut the unit down if the oxygen in the air is id dropped by 2%. Some states will not allow the ventless systems at all while others allow with a permit. Most states have no problem with them. Be sure to check the state codes in your area.

The direct vent system is the system that draws fresh air from the outside, uses this for combustion, and returns the by products back to the outdoors. This gas fireplace vent uses a coaxial pipe, like a smaller pipe inside a larger pipe. While the inner pipe will expel the used air, the fresh air brought in outer pipe will be heated by the inner pipe. This vent can be ran horizontally through the wall or vertically through the roof. Of course no chimney is required. The direct vent will require a gas fireplace mantel for the trim. Will use the enclosed front while the ventless fireplace will use an open front.

Most of the gas fireplaces can be used as a natural gas fireplaces or the propane gas fireplaces. Make sure which you will be needing before purchase. The natural gas will be hooked up to your house, like cable TV and you will receive a monthly statement. If you live outside the city, you may have to use propane. The propane company will install a large storage tank on your property and will deliver the propane gas as needed. The delivery will be based on how large the storage tank is and how much propane gas you use.