The key component needed to trigger a covered loss on equipment breakdown is a sudden and accidental event. This means that the damage or malfunction must occur unexpectedly and unintentionally. Power failure alone would not be enough to trigger a covered loss, as it is a common occurrence and not necessarily sudden or accidental. Rust and corrosion are also not sufficient, as they are gradual processes rather than sudden events. Therefore, the correct answer is sudden and accidental event.