These grilles are used on exteriors of buildings at air exhaust points in the HVAC system. The design of the grille utilizes louvers which are closed by default due to gravity. When air is exhausted through the system, it forces the louvers open for the duration of the exhaust sequence. The louvers then naturally close again with gravity, preventing any air intake. Please note per above that this louvers are by design not fixed open or adjustable, they open with force of exhaust air and fall shut with gravity. Versatile Applications: They can be used in various applications that require permanent large-scale ventilation combined with screening. This includes air exhaust for ventilation or air conditioning systems, plant rooms, generators, workshops, garages, and pumping stations. Robust Construction: Crafted from durable extruded aluminum sections, featuring a sturdy 2.0mm thick frame and 2.0mm thick blades. Anodized Aluminium :The standard finish is a aluminium anodized coating that not only protects but also enhances the aesthetic appeal with its classy design.