Bulk gas systems provide central storage and distribution of high-purity process gases used throughout the semiconductor fab. Common gases: Nitrogen (N2 - largest volume), oxygen, argon, hydrogen, helium, ammonia, silane, phosphine, arsine, and many specialty gases. Storage: Bulk liquid storage tanks (N2, O2, Ar, He) vaporized on demand. Tube trailer or cylinder storage for others. Purity grades: Electronic grade, ultra-high purity (UHP), semiconductor grade - ppb impurity levels. Distribution: Electropolished stainless steel piping, welded connections, point-of-use purifiers, mass flow controllers at tools. Pressure regulation: Step-down from tank pressure through multiple regulation stages to tool delivery pressure. Safety systems: Gas detection throughout fab, automatic shutoffs, ventilated gas cabinets for toxic gases, seismic bracing. Categories: Inert (N2, Ar), oxidizers (O2), flammables (H2, silane), toxics (PH3, AsH3), corrosives (Cl2, HCl). Each has specific handling requirements. Redundancy: Critical gases have backup supplies and N+1 delivery capability.