Vent free gas technology requires no flue systems. It utilizes tempered air from the home to supply the fire with oxygen. The particles of combustion are then distributed back into the room. Vent free products are tested to burn at an efficiency rate of 99.9%, which is the cleanest burning of any technology. Limitations exist with vent free products located in bathrooms, bedrooms & outdoor covered areas. Vent free gas technology is a controversial category within the hearth industry. There are manufactures and retail hearth dealers that believe it is the worst technology ever invented and there are others that believe it is the greatest. It is important to get all the information before deciding to purchase a vent free product.