A magnesium oxysulfate cleanroom panel and a rock wool cleanroom panel are both marketed as A1 non-combustible sandwich walls, but they are structurally opposite products. One is a rigid inorganic board made from magnesium oxysulfate cement reinforced with glass-fiber mesh. The other is a fibrous basalt slab bonded to face skins. That single difference decides moisture behavior, core stability, panel weight, screw-hold strength, cleanability and which GMP, hospital OR, food processing or fire-compartment project the wall can actually pass. This module sets the precise definition boundary for procurement engineers, cleanroom contractors, fire-protection subcontractors and project specifiers before RFQ release.