Disclosed are a method and an apparatus for solving mask precipitated defect issue. A gas is purged into a photomask reticle assembly for diffusing precipitated defects out of a photomask in the photomask reticle assembly. A metal shielding assembly enclosing the photomask reticle assembly is provided for reducing precipitated defects and damages to the photomask. In an illustrative embodiment, the metal shielding assembly comprises an upper metal shielding, a pellicle frame of the photomask reticle assembly, side support frames of the photomask reticle assembly, a top cover, a handle, and a handle cover.