Abstract: The invention concerns a window specially designed for emergency use. The window comprises a fixed outer frame (1) and a sash (2) mounted for normal horizontal pivoting movement between open and closed positions about axis Y--Y. Two arms (3) extend in the respective side rebates between the frame (1) and sash (2), and opposed horizontal pivots (6) are secured to the sash (2) and the arms (3) for such normal pivoting movement of the sash (2). Each arm (3) is connected to the top (1a) of the frame (1) by a hinge (4) and each arm is acted on by a respective telescopic gas spring (5) confined within the rebate but acting on the associated arm (3) to urge it outwardly of the frame (1). For normal opening and closing movement of the sash (2) for which a casement fastener (7) is fitted, the arms (3) are retained secured to the frame (1) by a catch arrangement that is operable manually by a control handle (8) separate to the fastener (7).