The Lockout-Verify Habit
Why this matters
Most fatal "I thought it was off" accidents share one root cause: someone controlled the energy but never verified it was actually gone. A switch can fail, a wrong breaker can get labeled, a second power feed can be forgotten, a capacitor can hold a charge after the panel is dead. Lockout and verify is the cheap, boring habit that stands between you and the one mistake you don't walk away from. It applies to electricity, pressure, stored mechanical energy, and anything else that can release while your hands are in it.
The two halves: lockout AND verify
People remember the lock and forget the verify, and the verify is what saves you.
- Lockout means putting the energy in the off/isolated state and physically preventing it from being restored. A lock and tag on the disconnect so no one, including you on autopilot, can re-energize it.
- Verify means proving, by measurement or test, that the energy is actually gone at the point you'll be working, not just that the switch is in the off position.
A locked-out system you didn't verify is a system you're trusting on faith. The lock stops someone else from turning it on. The verify confirms it was ever off.
The core sequence
Run this every time, in this order:
- Identify all energy sources. Electrical feeds (there may be more than one), stored electrical (capacitors, batteries), pressure (hydraulic, pneumatic, water, gas, refrigerant), stored mechanical (springs, suspended weight, raised components), and thermal.
- Shut down and isolate each source at the proper disconnect or shutoff, not at the user control.
- Lock and tag each isolation point. The tag says who, why, and don't touch.
- Release or block stored energy. Discharge capacitors, bleed pressure to zero, block anything that could drop or spring.
- Verify dead at the work point. For electrical, do the live-dead-live test below. For pressure, confirm zero on a gauge. For mechanical, confirm it can't move.
- Then work. And when you're done, reverse it deliberately: clear people, remove your lock, restore.
The live-dead-live test for electrical
This is the single most important verify step, and skipping it has killed careful people.
- Live: test your meter or tester on a known-energized source and confirm it reads voltage. This proves your tester works right now.
- Dead: test the equipment you locked out at the actual conductors and confirm zero.
- Live again: test your meter on the known source one more time, confirming it still works and didn't quietly fail between steps.
If the meter passed live, read dead on the equipment, and passed live again, you have proven the circuit is dead. Any other result means stop and reassess.
What people get wrong
| Mistake | Why it bites | The fix |
|---|---|---|
| Lock but no verify | Switch or label can be wrong | Always measure dead at the work point |
| Verify but no lock | Someone re-energizes while you work | Physical lock and tag, every time |
| One source isolated, others missed | Second feed or stored energy remains | List all sources before you start |
| Trusting a tester you didn't prove | A dead tester reads "safe" on everything | Live-dead-live, prove the tester |
| Removing someone else's lock | Person may still be in the equipment | Only the owner removes their own lock |
Stored energy is the silent one
Electrical gets the attention, but stored energy catches techs who did everything else right. A capacitor holds a lethal charge after the panel reads dead. A pressurized accumulator stays charged after the pump is off. A raised or spring-loaded component drops the instant you free it. Your isolation list has to include these, and your verify has to confirm each one is discharged or blocked, not just switched off upstream.
Make it a habit, not a decision
The reason to build this into muscle memory is that the dangerous days are the rushed, distracted, familiar ones, exactly when you're most tempted to skip a step on a system you've worked a hundred times. A habit you run automatically doesn't get skipped under pressure. Lock it, block it, verify it, every time, so the one time it actually mattered, you were already covered.
References
- OSHA 29 CFR 1910.147 (the control of hazardous energy, lockout/tagout).
- NFPA 70E (establishing an electrically safe work condition, verification).
- Manufacturer service documentation on energy isolation points and stored-energy discharge (generic).
- See related: The Energized Troubleshooting Stop Decision Tree; The Two-Person Rule for Dangerous Work.