Pressure cooking is the process of cooking food under high pressure steam, employing water or a water-based cooking liquid, in a sealed vessel known as a pressure cooker. High pressure limits boiling, and permits cooking temperatures well above 100 °C (212 °F) to be reached. The pressure cooker was invented in the seventeenth century by the physicist Denis Papin, and works by expelling air from the vessel, and trapping the steam produced from the boiling liquid inside. This raises the internal pressures and permits high cooking temperatures. This, together with high thermal heat transfer from the steam, cooks food far more quickly, often cooking in between half and a quarter the time for conventional boiling. After cooking, the steam pressure is lowered back to ambient atmospheric pressure, so that the vessel can be opened safely. Almost any food that can be cooked in steam or water-based liquids can be cooked in a pressure cooker.According to New York Times Magazine, 37% of U.S. households owned at least one pressure cooker in 1950. By 2011, that rate dropped to only 20%. Part of the decline has been attributed to fear of explosion, although this is extremely rare with modern pressure cookers, along with competition from other fast cooking devices, such as the microwave oven. However, third generation pressure cookers have multiple safety features and digital temperature control, do not vent steam during cooking, are more efficient and quieter, and these conveniences have helped make pressure cooking more popular again.