Pressure Cooking - Safety Features

Safety Features

Early pressure cookers equipped with only a primary safety valve risked explosion from food blocking the release valve. On modern pressure cookers, food residues blocking the steam vent or the liquid boiling dry would trigger additional safety devices. Modern pressure cookers sold from reputable manufacturers have sufficient safety features to prevent the pressure cooker itself from exploding. When excess pressure is released by a safety mechanism, debris of the food being cooked may also be ejected with the steam — sometimes forcefully with some noise. This can be avoided if the pressure cooker is regularly cleaned and maintained in accordance with the manufacturer's instructions and never overfilled with food and/or liquid. A pressure cooker should never be filled to more than 2⁄₃ its interior height with solid food, 1⁄₂ full for liquids and foods that foam and froth (e.g., rice, pasta), and no more than 1⁄₃ full for pulses (e.g. lentils). A tablespoon of cooking oil can be added to minimise foaming.p. 262

Modern pressure cookers typically have two or three redundant safety valves and some additional safety features, such as an interlock lid that prevents the user from opening the lid when the internal pressure exceeds atmospheric pressure, preventing accidents from a sudden release of hot liquid, steam and food. If any safety mechanisms are not correctly in place, the cooker will not pressurize the contents. Pressure cookers should be operated only after reading the instruction manual because each model has slightly different safety mechanisms.

For first generation pressure cookers with a weighted valve or "jiggler", the primary safety valve or regulator is usually a weighted stopper, commonly called "the rocker" or "vent weight". This weighted stopper is lifted by the steam pressure, allowing excess pressure to be released. There is a backup pressure release mechanism that releases pressure quickly if the primary pressure release mechanism fails (e.g., food jams the steam discharge path). One such method is a hole in the lid that is blocked by a low melting point alloy plug and another is a rubber grommet with a metal insert at the center. At a sufficiently high pressure, the grommet will distort and the insert will blow out of its mounting hole to release pressure. If the pressure continues to increase, the grommet itself will blow out to release pressure. These safety devices usually require replacement if they are activated by excess pressure. Newer pressure cookers may have a self-resettable spring device, fixed onto the lid, that releases excess pressure.

For second generation pressure cookers with selectable pressure and (often hidden) spring valve operation, a common safety feature is the gasket, which expands and releases excess pressure downward between the lid and the pot. This release of excess pressure is forceful and sufficient to extinguish the flame of a gas stove.

Pressure cookers sold in the European Union (EU) must comply with the Pressure Equipment Directive.