An electrical panel is being serviced using lockout/tagout procedures. The main disconnect is locked out, but the panel is fed by multiple sources. What additional step is required?

Option B: Post warning signs around the work area

While posting warning signs is a good safety practice and may be required, it is not sufficient by itself when multiple energy sources remain active. Signs do not physically prevent electrical contact or eliminate the hazard. The primary requirement is to physically isolate all energy sources through proper lockout procedures before any warning signage becomes meaningful.

Option C: Have an electrician verify the lockout

Having an electrician verify the lockout is valuable but secondary to the fundamental requirement of actually locking out all energy sources. Verification cannot substitute for proper isolation of energized circuits. The electrician's verification would be meaningless if energy sources remain unlocked and potentially active, creating ongoing electrical hazards for workers.

Option D: Test the circuit with a voltmeter only

Testing with a voltmeter is part of verification procedures but does not eliminate the hazard. Testing only confirms the presence or absence of voltage at a specific moment and location. Without physically locking out all energy sources, circuits could become re-energized at any time, making voltage testing insufficient for ensuring ongoing worker safety during maintenance activities.