Verification Best Practices
How to write and perform effective zero-energy verification for every type of hazardous energy.
What is verification
Verification is the step that proves energy isolation actually worked. It is not optional. Every LOTO procedure step must include a verification action. OSHA and industry standards require verifying zero energy state before work begins, and your written verification instructions are the frontline worker's guide to doing that correctly.
The try-start-try method
After locking out, attempt to start or operate the equipment using its normal controls. The equipment should not respond. If it does, isolation is incomplete: stop immediately and re-check all isolation points. After confirming the equipment cannot start, return all controls to the OFF or neutral position before proceeding. This method is the gold standard for electrical and mechanical isolation verification.
Tips
- Always return controls to OFF after testing: a machine that starts unexpectedly when locks are removed can cause serious injury.
- If the equipment has multiple start stations, test from each one.
Zero-energy verification by energy type
- Electrical: Use a calibrated, functional voltmeter. Test the meter on a known live source first, then test the isolated circuit (each phase to ground and phase to phase), then test the meter on the known live source again to confirm it still works. All readings must show zero.
- Hydraulic / Pneumatic: Bleed pressure to zero and observe the gauge. Physically attempt to move the actuator or cylinder. If it moves at all, pressure is still present. Block or restrain any suspended loads.
- Mechanical (gravity / moving parts / spring): Physically try to move the component. If it can be moved by hand, it is not isolated. Use blocks, pins, or restraints. For spring-loaded mechanisms, confirm the spring is fully released or physically blocked.
- Chemical / Fluid: Verify valves are closed and locked. Check downstream pressure gauges. If possible, crack a downstream bleed port to confirm zero flow. Use double block and bleed for high-hazard chemical services.
- Thermal (steam / hot water): Allow components to cool to ambient temperature. Use a temperature gun or thermal strip to verify. Never rely on touch alone: pipes can appear cool on the outside while still containing pressurized steam internally.
- Radiation: Follow site-specific radiation safety protocols. Use a survey meter to confirm source is shielded or de-energized. These procedures should always be written by qualified radiation safety personnel.
Tips
- Use the unit from the energy type selection (Volts AC, PSI, °F) to guide what measurement tool is needed.
- If the verification method requires a specific tool, name that tool in the verification text.
When verification fails
If you cannot confirm zero energy state, STOP. Do not proceed with work. Re-check every isolation point in order. Verify that the correct device was locked. It is easy to lock the wrong breaker or valve in a crowded panel. If you are still unable to achieve zero energy after re-checking, escalate to your supervisor or safety lead. Never bypass verification just because the equipment "looks" safe.
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