The chair rose and fell in a few minutes. What happened? I can't adjust it.

The computer chair you described is pneumatic. The height of the chair can be adjusted within a limited range through the spring installed on the column and the cylinder sleeved on the column.

There must be a phenomenon that the seat cannot be adjusted, which means that the spring is good and the cylinder is broken. It is common that the throttle valve connected with the wrench for adjusting the height is not sealed, resulting in air leakage in the cylinder.

The main reason is the aging or wear of the throttle sealing ring. Maintenance is to replace the same sealing ring as much as possible.