Abstract: A chair wherein the leg contains a gas spring which can be actuated to raise or lower a carrier for the seat and back rest. The seat is rigid wtih the carrier but the back rest is pivotally connected with the seat by hinge which contains a torque bar tending to pivot the back rest forwardly. Such pivoting of the back rest is normally prevented by a damper which operates between the carrier and a support at the lower end of the back rest and can be blocked to maintain the back rest in a selected angular position. The damper can be unblocked by a first mechanism at one side of and beneath the seat, and the gas spring can be activated by a mechanism beneath the other side of the seat.