1,029,830. Ventilators. COLT VENTILATION & HEATING Ltd. Dec. 18, 1963 [Dec. 18, 1962], No. 47843/62. Heading F4V. [Also in Divisions A5 and F2] Two hinged cover-plates of a roof ventilator are normally held closed and are automatically opened in the event of fire acting on fire-detecting means. As illustrated, the roof ventilator comprises a throat 14, fixed side baffles 23 and end plates 15, and overplates 17 hinged at 18. The plates are normally held closed by cords 27 connected to a further cord by a link which fuses in the event of fire to allow springs 26 to move the plates to the fully open position. Side openings 20 of the ventilator are controlled by closure plates 29 pivoted at 30 and biased to the closed position by springs 31. The closure plates are normally operated by pneumatic piston and cylinder assemblies 32 supplied from a common compressed air source, Fig. 6 (not shown). The air line includes a connection to atmosphere, Fig. 7 (not shown), which is normally closed but which in the event of fire opens to allow the springs 31 to close the plates 29 and also to shut off the compressed air supply. In an alternative arrangement, Fig. 8 (not shown), springs 62 bias the cover plates 17 to the open position, this bias being over-ridden by springs 60 including fusible links 61. The plates 17 may be independently operated by pneumatic cylinder and piston assemblies 63, the plates 17 being held in engagement with the piston rods 64 by the springs 60. A manual valve 43 allows compressed air from a source 40 to open the plates or connects the cylinders 63 to atmosphere to close the plates. A valve 38 similarly controls the closure plates 29. A further valve 39 in the air supply to the piston and cylinder assemblies 32 is connected to the supply to the assemblies 63 so that when valve 43 passes compressed air to open the plates 17 compressed air is allowed to escape from assemblies 32, thus closing the plates 29 and vice versa. As described above, in the event of fire, the plates 17 open and the plates 29 close. In modifications, not shown, the cover plates 17 may be biased to open by weights and the means detecting the presence of fire to open the cover plates may be a device responsive to thermal radiation, rate of charge of temperature, light or sound.