CLEANROOM FLUSH FILTERED CEILING GRID [AND PLENUM] [AND ...

Walkable Return Air Pans: Walkable return air pans shall be constructed of 14 gauge steel [aluminum] [stainless steel] with 3/8" diameter perforations to form a 51% open area. Reinforcement shall consist of 0.375 inch flat bar that is welded to pan. [The finish of the panel is to match the ceiling grid finish.] ................
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