Flash Test: Most operators reserve this test for leads for fear of causing damage to internal components such as suppression capacitors. It is sometimes used on equipment which has undergone a complete rebuild or renovation. It is then considered useful as a check after re-assembly that no cables have been trapped or damaged by fitting the equipment casing. Never apply this test to electronic or IT equipment.

A nominal test voltage is 1.5Kv for Class 1 and 3.00Kv for Class 2 is used. The test should only be used with extreme caution, and with particular regard for the safety of testing staff and any bystanders.