Electrical apparatus intended for use in explosive gas atmospheres under conditions where the hazard will be from combustible dust. Electrical apparatus is considered acceptable if it operates safely in an enclosure with a maximum dust layer thickness of five millimetres on its external surface.Cross References: BS 31*BS 4121*BS 4568:Part 1*BS 4568:Part 2*BS 4999:Part 101*BS 5345:Part 1*BS 5345:Part 2*BS 5501:Part 1*BS 5501:Part 2*BS 5501:Part 3*BS 5501:Part 4*BS 5501:Part 5*BS 5501:Part 6*BS 5501:Part 7*BS 5501:Part 8*BS 5501:Part 9*BS 5958:Part 2*BS 6069:Part 2*BS 6121:Part 1*BS 6207*BS 6467:Part 1*BS 6467:Part 2*BS 6480*BS 6651*BS 6656*BS 6941*BS 7361*BS 7430*IP 5X*IP 6X*IP 54*IEC 79:Part 15*IEE Regulations for Electrical Installations*82/24413 DC*BEAMA/AEMT Code of Practice for Repair of Ex apparatus*