Electrical Safety Standards (Subpart S)
Framework
Subpart S (1910.301–.399) is drawn largely from the National Electrical Code. Key sections: 1910.303 general requirements (installation, working clearances), 1910.304 wiring design and protection, 1910.305 wiring methods and flexible cords, 1910.332 training, 1910.333 work practices, 1910.334 portable equipment and cords, and 1910.335 safeguards for personnel protection.
Qualified vs. unqualified
An unqualified person is trained in and familiar with the safety-related work practices needed for the task but not the construction and operation of the equipment; a qualified person understands the equipment and hazards and has received specific training. Both must be trained before exposure. Unqualified employees may not work near exposed energized parts - keep at least 10 feet from exposed live parts on systems of 300 volts or less; qualified persons may approach closer only under the qualified-person provisions and Table S-5 distances.
Work practices
Live parts must be de-energized before work unless de-energizing creates a greater hazard or is infeasible. The sequence: disconnect, lock out and tag, release stored energy, and verify de-energization with test equipment. Flexible cords must not be used as permanent wiring, may not be spliced to extend length, and must be protected from strain and damage. Working space in front of electrical equipment (600 V or less) is at least 3 feet deep, 30 inches wide, and 6.5 feet high, and must not be used for storage.
Traps
Questions often blur "de-energized" with "locked out" - both are required, plus verification. Another trap: assuming a hazard assessment alone satisfies training; 1910.332 requires documented, task-specific training.
Worked example
A mechanic needs to replace a motor starter. Correct path: notify affected employees, open the disconnect, apply lock and tag, test at the load side with a meter rated for the voltage, then work - and treat the circuit as energized if it cannot be locked.