Absence of voltage testing is a vital step in the process of verifying and establishing a de-energized state of any electrical system. As detailed in NFPA 70E clause 4.2.5., there is a specific and approved approach to establishing an electrical safe work condition with the following steps:

• determine all possible source of electrical supply
• interrupt the load current, open the disconnecting device for each possible source
• verify where possible that all blades of the disconnecting devices are open
• release or block any stored energy
• apply lockout device in accordance with documented and established work procedures
• using an adequately rated portable test instrument to test each phase conductor or circuit part to verify it is de-energized. Test each phase conductor or circuit path both phase-to-phase and phase-to-ground. Before and after each test, determine that the test instrument is operating satisfactorily through verification on any known voltage source

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