All pressure cookers have the same principles of operation. Heat produces steam in an a closed container which raises the boiling point to cook foods faster. A pressure cooker cooks food in superheated steam, it is not a boiler so there is no reason to submerge foods in water.
There are two basic types of pressure cookers. The old style, first generation pressure cooker with some type of weighted, or "jiggle top" pressure regulator which sits a top the vent pipe on the lid, or the newer style, the second generation which is a closed system and uses spring valves.
Every time you use any pressure cooker it should be thoroughly inspected. The cooker should be clean, inside and out, with no food particles or debris on the rim of the pot, or the lid. There should be no sign of warping, dents or dings, or any other damage to the rim of the cooker or lid. Remove and examine the gasket. The gasket should be in good condition with no signs of cracking, tears or other deterioration such as gumminess or brittleness. Replace the rubber/silicon parts at the first sign of deterioration. The gasket should fit snugly in its place in the lid. If using a jiggle top pressure cooker always check the vent pipe to make sure it is clear and open. On a valve type cooker, lift or turn the valve to make sure it moves freely and the inside connecting screw is tight. Periodically check the handles and tightened the screws as necessary. Read more about the care and cleaning for your pressure cooker, the lid and gasket.
