All 120-volt, single-phase, 15- and 20-ampere receptacle outlets on construction sites that are not a part of the permanent wiring must have GFCI protection. An assured equipment grounding conductor program is an alternative (but GFCI is strongly preferred). Flexible cords must be 3-wire with grounding conductor. Extension cords must be hard-usage or extra-hard-usage rated (S, ST, SO, STO type). Temporary wiring must be protected from physical damage. All electrical installations must comply with NEC (NFPA 70). Lockout/tagout per 1926.417 required before working on electrical systems. Electrocution is one of OSHA Construction Fatal Four — approximately 8% of construction fatalities. Training required: qualified persons for electrical work, unqualified persons for hazard awareness.