Grounding of Metal Cabinets: Metal explosion-proof distribution boxes must be reliably grounded, with the grounding wire connected to the cabinet's outer shell. For three-phase systems without a neutral wire, the grounding wire should have a cross-sectional area of at least 4mm². 1 I When does electrostatic charging occur in practice? 2 I How does. Hazardous industrial environments — such as chemical plants, oil refineries, pharmaceutical production lines, and grain processing facilities — are often at risk of explosions due to the presence of flammable gases, vapors, or dust. Therefore, internal faults are safe. Electrical sparks or static electricity can ignite the combustible gasses, vapors, or dust that are common in these settings. Proper grounding reduces the.