Editing Pressure cooker (section)

=== Gasket ===
A gasket or sealing ring, made from either rubber or [[silicone]], forms a gas-tight seal that does not allow air or steam to escape between the lid and pan. Normally, the only way steam can escape is through a [[Pressure regulator|regulator]] on the lid while the cooker is pressurized. If the regulator becomes blocked, a [[safety valve]] provides a backup escape route for steam.{{citation needed|date=September 2019}}

To seal the gasket there are several main methods used. Each determines the design of the pressure cooker:
* The ''twist-on'' design has slots on the lid engaging with [[flange]]s on the body, similar to a lid on a glass jar, that works by placing the lid on the pot and twisting it about 30° to lock it in place. A common modern design, it has easily implemented locking features that prevent the removal of the lid while under pressure.
* The ''center screw'' design has a bar that is slotted in place over the lid and a screw tightened downward to hold the lid on. Though an older design, it is still produced due to its ease of construction and simplicity.
* The ''bolt-down'' design has flanges on both its lid and its body for bolts to be passed through, and usually uses [[Wingnut (hardware)|wingnuts]] that hinge on the body and so are never fully removed from the cooker; this sealing design is typically used for larger units such as canning retorts and autoclaves. It is very simple to produce, and it can seal with simple and inexpensive [[gaskets]].
* The ''internally fitted lid'' design employs an oval lid that is placed inside and presses outward; the user inserts the lid at an angle, then turns the lid to align it with the pot opening on top because the lid is larger than the opening. A spring arrangement holds the lid in place until the pressure forms and holds the lid tightly against the body, preventing removal until the pressure is released.

[[Gasket]]s (sealing rings) require special care when cleaning (e.g., not washed with kitchen knives), unlike a standard [[lid (container)|lid]] for a saucepan. Food debris, fats, and oils must be cleaned from the gasket after every use. Gasket/sealing rings need replacing with a new one about once a year (or sooner if it is damaged e.g. a small split). A very dry gasket can make it difficult or impossible to close the lid. Smearing the gasket sparingly with vegetable oil alleviates this problem (using too much vegetable oil can make the gasket swell and prevent it sealing properly). A gasket that has lost its flexibility makes bringing the cooker up to pressure difficult as steam can escape before sufficient pressure is generated to provide an adequate seal; this is usually a sign that the gasket needs replacing with a new one.  Oiling the gasket with vegetable oil may alleviate the problem temporarily, but a new gasket is often required.{{Original research inline|date=December 2022}}

Pressure cooker manufacturers sell replacement gaskets and recommend their replacement at regular intervals e.g. annually.
If the pressure cooker has not been used for a long time, the gasket and other rubber or silicone parts will dry out and will likely need replacing.