Physics of pollution flashover

The apparent paradox in pollution flashover is that catastrophic electrical discharges are produced, spanning up to metres of air, by electrical potential differences capable, in ordinary circumstances, of being contained by air clearances of the order of a few centimetres. In some way, the presence of feebly conducting deposits, on a surface which otherwise would be highly insulating, lowers the effective electric strength of the surface by a factor not far short of 100.