| 摘要 |
A controllable air vent casing for securement to a side wall of a buildi ng structure, such as agricultural structures housing farm animals, is described. The air vent casing is secured about one or more openings provided in the side wall of the building structure to control the passage of outside ambient air with an inner space of the building structure. The casing comprises side walls and a front air passage restricting panel through which ambient air is drawn. The air passage restricting panel or one of the side panels is hinged whereby to constitute an adjustable trap wall whereby to create a side opening to permit ambient air behind the air passage restricting panel, when it is required to admit more fresh air within the building structure.
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