Explosion-proof Junction Boxes BHD51 Series Explosion-proof Junction Boxes 1)Explosion protection to-CENELEC-IEC-NEC2)Can be used inZone 1 and Zone 2Zone 21 and Zone 223)Six types: A, B, C, D, E, F.Type A, B, C, D, E in copper-free aluminium only;Type F in copper-free aluminium or cast iron.