Random events are arcing or sparking. This conductivity prolongs the arcing due to cascading failure of the surface. They protect power line insulators from damage due to arcing. The steel wick must be oxidized to prevent arcing of the coil. Glass may also be damaged by high-voltage arcing. A fire was started by electrical arcing. Grissom had initiated the retrorocket sequence and the spacecraft was arcing downward. More nitrogen is used in higher-voltage lamps to reduce the possibility of arcing. Otherwise the damaging effect of arcing will be split evenly across both contactors. The contact area of the switch is constructed of materials that resist corrosion and arcing. The arcing can oxidize, pit and melt the contacts. A special output connector is used that prevents arcing, insulation breakdown and accidental human contact. The AFCI will open the circuit if dangerous arcing is detected. On the CVR, NTSB investigators heard eight sounds of electrical arcing beginning at 18&colon;48. This prevents any arcing on the power pins, prolonging their lifespan.