A fireplace is an open hearth used for heating, to make fire, and sometimes as part of a chimney. Fireplaces can be built into the wall or floor in the room where they are located, but often have their own dedicated space on another outside wall. Many modern home improvement and building codes limit indoor wood-burning fireplaces due to concerns about air pollution in recent years; however, some homes still use them because it was not unusual that one had been there when they bought the house. A fireplace typically uses oxygen from the surrounding area instead of pressurized tanked gas so operating costs will likely be higher than those using tanked gas supply. The hot gasses produced by combustion heat up the fire. Fireplaces have a hood above the flame to capture some of these products and help them up soot in chimneys especially when burning wood or coal, while the air was pulled through underneath (for instance by use of the famous living-room fireplace on Downton Abbey). This airflow provided more complete combustion on-demand with less need for flue work, plus it helped regulate creosote buildup in the interior of the chimney.