adjustable grille

[EN 12792:2003, 196]:
grille intended to vary the direction or directions of the air delivered to the treated space. It consists of one or more series of adjustable parallel ribsfixed directional grille

[EN 12792:2003, 196]:
grille intended to diffuse the air in one or more fixed directions. It consists of one or more series of fixed parallel ribsfixed non-directional grille

[EN 12792:2003, 196]:
grille not intended to change the direction of air. It can consist of parallel laminae, ribs, perforated metal, grid, wired grid, etc.3.17