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This article presents evidence that a major cause of residential lightning fires is electrical arc-fault current. Such arc-fault currents are a common result of both direct and indirect lightning strikes. These faults result from lightning overvoltage damage to the insulation of electricity supply conductors and appliances. Many of these overvoltages appear to be caused by indirect lightning strikes, and a small fraction of these events also result in damage to fuel gas systems, especially thin, metallic, flexible gas lines. Fuel gas leaks resulting from this electrical damage may contribute to the fire hazard. The absence of any lightning protection on residences with exposed metallic roof penetrations is considered a major factor.