These units usually stand away from the wall and are very similar to a wood burning stove in appearance. Available for direct vent, vented and vent-free applications.
Coaxial vent system of a pipe inside a pipe (generally 4"/7") the inside pipe is for exhaust, while the outer pipe brings in outside air for combustion. The design of these fireplaces allow for a completely sealed system that does not compromise inside air quality of your home. It also lets you vent a product horizontally (great for when an appliance is installed on an outside wall). Direct vent appliances are usually limited to a length of 40ft (with a maximum horizontal length of 15ft) that will allow an appliance to function properly.
FDV451 featured above