A tension adjust device (20) for a chair comprises a carrier member (21), an actuation member (22), a ratchet mechanism and a disengagement mechanism. The actuation member (22) is rotatable in a first direction and in a second direction opposite to the first direction and is coupled to the carrier member (21) to rotate the carrier member (21). The ratchet mechanism (31-33) is coupled between the actuation member (22) and the carrier member (21) and comprises a locking pawl (31) and a profile (32) having a plurality of recesses for engagement with the locking pawl (31). The disengagement mechanism is configured to maintain the ratchet mechanism (31-33) in a disengaged state when the actuation member (22) rotates the carrier member (21) in the second direction. The locking pawl (31) remains disengaged from the recesses of the profile (32) while the ratchet mechanism (31-33) is in the disengaged state.