heated by natural gas with the burner recessed below the stovetop. In areas where natural gas is unavailable, LPG may be used instead. With the adoption of gas and its less objectionable combustion products, the chimney has been replaced by the vent hood. This type of stove allows foods to be stir-fried at a very high heat, sometimes hot enough to deform the wok itself. Professional chefs in Chinese restaurants often use pit stoves since they have the heating power to give food an alluring . Gas Traditionally shaped woks can be used on some Western-style (flat-topped) gas stoves by removing a burner cover and replacing it with a "wok ring", which provides stability and concentrates heat. Although not as ideal as "pit stoves", these allow woks to be used in a manner more suitable for their design and are good enough for most tasks required in home cooking. Wok rings are sold in cylindrical and conical shapes. For greatest efficiency with the conical wok ring, position it with the wide side up. This allows the base of the wok to sit closer to the heat source. In recent years, some consumer indoor stoves using natural gas or propane have begun offering higher-BTU burners. A few manufacturers of such stoves, notably Kenmore Appliances and Viking Range Corp. now include a specially designed high-output bridge-type wok burner as part of their standard or optional equipment, though even high-heat models are limited to a maximum of around 27,000 BTU (7.9 kW). Because of the high cost of kitchen modifications, coupled with increased heat and smoke generated in the kitchen, more home chefs are using their wok outdoors on high-heat propane burners with curved wok support grates. Many inexpensive propane burners are easily capable of 60,000–75,000 BTU (17.5–22 kW) or more, easily surpassing most in-home gas stoves. Electric Woks, round or flat bottomed, do not generally work well for stir-frying or other quick cooking methods when used on an electric cooker. These stoves do not produce the large amounts of quick even heat required for stir-frying. It is possible, however, to find round-shaped electric stove elements that will fit the curve of a wok, which allows the wok to be heated at its bottom along with part of its sides. A flat-bottomed wok may also work better on an electric stove. Coupled with the lower heat retention of woks, meals stir-fried on electric