What does 'zero energy' mean in Lockout/Tagout procedures?

• A. Only unplugging electrical power is required.
• B. All energy sources are energized for testing.
• C. Energy sources are ignored if the work is brief.
• D. All energy sources are isolated, locked out, and verified de-energized before work begins.

Answer: (D)

Zero energy means there is no energy available to cause unexpected start-up or movement while work is being done. To reach this state, every energy source must be isolated, locked out to prevent re-energization, and verified de-energized before anyone begins work. This covers electrical, mechanical, hydraulic, pneumatic, chemical, and thermal energies, plus any stored or residual energy such as springs, capacitors, or gravity. The lockout device physically prevents the energy source from being re-energized, and a tag communicates that the equipment is out of service. This protects workers from sudden releases or startup during maintenance or setup. The other options fail because they either leave energy sources accessible, allow testing with energy on, or ignore stored energy, all of which create a risk of injury.