Depending on the type of fire you select you may need to have a chimney or flue to install Marble Fireplaces. Electric Fireplaces can be installed against a flat wall and no not need to be vented in any way. The main advantage of these type of fireplaces are that they do not emit any type of fumes and simply need a power source to work (plug and play appliance effectively). Gas fireplaces are completely different and almost always need some sort of vent to work.  Slim line gas fireplaces or multi flue gas fireplaces are compatible with Class 1, Class 2 and Pre cast flues and would hence work with all types of chimneys.  However some deep fires need a class 1, traditional brick chimney to work. Flue less gas fireplaces require an air brick to be created in your living room, but do not require a chimney or vent. Balanced Flue or power flue gas fireplaces require an external vent to be created from an exterior wall. They do not need a chimney, but vent the fumes out of a horizontal pipe. Balanced Flue gas fireplaces have a glass screen in front of the flame are frequently more energy efficient. They also have the benefit of being arguably safer for families with children. Many homeowners however do not like balanced flue fireplaces are they do not have an open living flame effect, and can easily be mistaken for an electric fireplace. . Power flue fireplaces do not have a glass screen in front of them, and have a more realistic flame effect. However, power flue gas fireplaces have the disadvantage of creating a draft in the room, as there is an open vent to an exterior wall effectively.