Causes for Explosions
Old pressure cookers had no valves to release the tremendous pressure caused by steam inside heated to the boiling point. If the cooker was not removed from the stove or unplugged in the appropriate amount of time, the lid would fly off and the pot's fiery hot contents would splatter.
Pressure cookers now have emergency regulators that permit steam to discharge during the cooking process before it reaches unsafe levels of intensity. They are also equipped with manual pressure valves that prevent removing the lid before the steam has dissipated to harmless levels.
Pressure cookers from the past are sold at online auctions and garage sales and are often passed from one generation to another as family mementos. They should be reserved for display or conversation pieces but never used for cooking.