Understanding Electrical Hazards at 120VAC and 208VAC
- Jeff Kershner
- May 19
- 2 min read
Electrical workers often underestimate the hazards of lower voltages like 120VAC and 208VAC. It’s important to consider the risks of shock and arc flash separately.
Shock Hazards
120VAC Shock Risk
According to NFPA 70E 2024 - 130.4(G)(1), no qualified person should approach or bring any conductive object closer to exposed energized electrical conductors or circuit parts than the restricted approach boundary.
Restricted Approach Boundary for 120VAC: "Avoid contact" per NFPA 70E 2024 Table 130.4(E)(a).
Definition of Exposed Conductors: Capable of being inadvertently touched or approached nearer than a safe distance by a person.
Key Question: Can you avoid contact without trying?
No exposed energized conductors: No PPE needed.
Inadvertent contact possible: Rubber insulating gloves are required (e.g., using a multimeter).
More details are available in our related article "Debunking Low Voltage Myths: Why 120 Volts Isn’t as Safe as You Think".
208VAC Shock Risk
Restricted Approach Boundary for 208VAC: 12 inches.
Standard Safe Work Practices: Required under NFPA 70E 2024 (e.g., insulated gloves/tools).
Refer to our workplace poster for a detailed explanation of boundary requirements.
Arc Flash Hazards
120VAC Arc Flash Risk
120VAC single-phase systems have not been shown to create an arc flash hazard greater than 1.2 cal/cm² at 18" working distance.
Supporting Research: "Arc Flash in Single Phase Power Distribution," IEEE Paper No. ESW2024-33 (John F. Wade, Terry W. Becker).
Additional Risk: Small metal ejections are possible during a 120VAC fault, so eye protection and appropriate safety gear should still be considered.
208VAC Arc Flash Risk
208VAC three-phase systems may create an arc flash hazard.
Refer to: Equipment labeling or include in your arc flash evaluation.
Example: Simple tasks like turning a breaker on/off at 208VAC need careful evaluation.
Refer to NFPA 70E 2024 110.2(B) Exception No. 1:
Normal operation is only permitted when equipment is:
Properly installed.
Properly maintained.
Rated for available fault current.
Used per listing and manufacturer instructions.
And:
Doors and covers are closed and secured.
There is no evidence of impending failure.
If a breaker trips -- or circuit work has been performed while off -- it is no longer normal operation.
Key Takeaways
Never assume low voltages are risk-free.
120VAC presents a shock risk, though arc flash risk is minimal.
208VAC presents both shock and arc flash risks.
Standards define minimum requirements. Facility-specific PPE rules should be followed if they are stricter. Trust Guidant's electrical safety experts to help you understand the true risks and ensure the right protection at every voltage.
