There are two or three holes in the lid of the pressure cooker, and there is a piston in the middle hole to keep the pressure in the cooker when burning;

There is also a small hole on the side to ensure safety. If the hole in the middle is blocked and you don't know it, it will explode if you continue to burn.

Small holes are usually pressed out by aluminum sheets. Only when the pressure is too high can the aluminum sheets be punched through by the pressure and play a safety role.

~~LZ depends on the accessories (if it is 10 year, it should be lost = =||, press the small hole with the aluminum sheet in the accessories, otherwise there will be no pressure inside and outside, just like an ordinary pot.