- Does the electrical guarding requirement at 29 CFR 1910.303(g)(2)(i) apply to voltages below 60 volts DC?
- Will OSHA treat a failure to guard live parts operating below 60 volts DC as a de minimis violation?
- The requirement applies to live parts operating at 50 volts or more AC or DC. The requirement does not distinguish between AC and DC voltages.
- For a violation to be considered de minimus, the employer must be found to have deviated from OSHA standard requirements in a way that did not directly cause employee injury or contribute to employee health issues.
“You point out in your letter that some consensus standards consider live parts operating between 50 and 60 volts, DC, to be non-hazardous under certain circumstances. However, OSHA considers all voltages of 50 volts or above to be hazardous. Electric current, not voltage, passing through the human body causes injury, and the amount of current passing through an object depends on the resistance of the object. As explained in Appendix C to 29 CFR 1910.269, the internal resistance of the human body is 500 ohms, which is the minimum resistance of a worker with broken skin at the point of contact. The current through 500 ohms from a live part energized at 60 volts would be 120 milliamperes. This level of current, either ac or dc, is sufficient to cause serious injury.” (Boldface added by e-Hazard.)
OSHA pointed out that serious injuries occurred in situations where the worker was exposed to only 12 volt- or 24-volt DC vehicle batteries. While their 1910 standard states guarding is necessary for electrical equipment for 50V and above, the letter states that equipment under 50 volts is not always completely safe, either.
Due to the limits of a de minimus definition and in the light of what actually causes electrical injury, a violation of 1910.303(g)(2)(i) would NOT be considered a de minimus violation.
In our Low Voltage and High Voltage classes, we at e-Hazard stress the importance of creating an electrically-safe work condition. Even at voltages less than 50V AC or DC, hazardous situations can be presented to the electrical worker due to high amperage sources, explosive potential, or excessive electrical arcing. Electrical safety is only assured with a proper workplace hazard evaluation, and energized work less than 50 volts (AC or DC) needs to fall in line with the requirements of NFPA 70E 130.2(A)(3).