Final answer:
If firefighters and equipment need to enter into Zones 3 or 4, the personnel who should remain and initiate a quench and verify the magnetic field is stable.
Step-by-step explanation:
If firefighters and equipment need to enter into Zones 3 or 4, the personnel who should remain and initiate a quench and verify the magnetic field is stable. Zone 3 and 4 have higher risks and the stability of the magnetic field is crucial in those areas. The magnetic field should be stable to ensure the safety of the firefighters and equipment.