A slot ventilator (100, 500) comprises a slotted backing member (24, 124, 424, 524), an elongate facing strip (26, 126, 426, 526, 626), and a linkage mechanism connecting the backing member and facing strip with one another, the linkage mechanism being arranged to permit generally translational forward and backward movement of the facing strip between a closed position in which the slot is closed and an open position in which the facing strip is spaced in front of the backing member. The linkage mechanism includes a hinge (58, 158, 300) allowing the facing strip to rotate about a longitudinal axis to vary the angular orientation thereof. When installed horizontally in a window frame (14, 588, 588'), the facing strip may be moved forwards and backwards to increase and decrease ventilation, and may be rotated about the hinge to divide incoming ventilation favourably between downward and upward directions.