Building air and smoke vent - has frame with Z=section side walls, whose upper flanges slope inwards and downwards

The air, heat and smoke venting service has a sheet metal base frame fitted over a rectangular roof opening, with a hinged vent flap. A further cover, opening automatically in the event of excessive smoke of heat, is hinged to the flap. The base frame (1) has a Z-section side walls, whose upper flanges extend inwards and slope towards the roof at an angle of roughly 15 deg.. A sheet metal tilting frame (2) fits into the flanges, preferably with a seal in between and is hinged on the frame at the side nearest the roof ridge. It can be opened by a cylinder etc. into a position, where it is inclined at roughly 5 deg. in the same direction as the complete unit.