A masonry fireplace can be converted to gas by installing a gas insert. While some people enjoy the look of flames inside a picture frame, others prefer the open hearth look. For them, gas log units can be placed inside a fireplace, but as these are open to the room, the efficiencies normally gained with gas are lost. Gas burns clean, but these open units require some maintenance because dust or pet hair can get onto the logs, says Mark Burlbaw, president of Mark & Buttons, a full-service chimney sweep and masonry repair company in Owings Mills. Otherwise, the maintenance with gas is minimal.