You who read this blog are a curious bunch. When I write that a consensus standard is the minimum of what is expected of you, comments pour in that a standard is a best practice or that requirements would never be the absolute safest. Then when I post that you must first attempt to eliminate a hazard, the comments pour in from the other direction. A hazard cannot be eliminated so just start at the next control or that is no need to even consider elimination as an option. Some of the comments regarding both blogs are from the same people even though the concepts being discussed are contradictory.
I commend all of you who go beyond the minimum requirements. Whether you realize it or not, most of you do exceed the requirements. I also typically exceed the requirements of a standard. However, when someone asks me about the specific use of a standard, my answers are limited to the requirements of the standard. I can only mention that additional steps, actions or requirements may be prudent. Why do I say that it is a contradiction to have a mindset that a standard is the most you can do yet think elimination is not possible? Why can’t it be both ways?
NFPA 70E®, Standard for Electrical Safety in the Workplace® currently protects employees from two defined electrical hazards; shock and arc-flash. What voltage level is necessary for a shock hazard to exist? A shock hazard in NFPA 70E is defined as a source of possible injury or damage to health associated with current through the body caused by contact or approach to energized electrical conductors or circuit parts. This definition includes an informational note that injury and damage to health resulting from shock is dependent on the magnitude of the electrical current, the power source frequency (e.g., 60 Hz, 50 Hz, dc), and the path and time duration of current through the body. The physiological reaction ranges from perception, muscular contractions, inability to let go, ventricular fibrillation, tissue burns, and death.
The consensus standard does not require that an electrically safe work condition be established when the voltage is less than 50 volts. There are no specified approach boundaries so there are no approach boundaries to drive the need for an energized work permit. There are no boundaries to base the need for shock protection. Below 50 volts, the shock risk assessment must determine if there is a risk of an arc-flash or electrical burns. If these additional hazards are not present, NFPA 70E does not require that the equipment be shut off or that PPE be used. Does this mean that you cannot be electrocuted or even suffer a shock at a voltage less than 50 volts? No, either may could occur under the right conditions. In the field, what constitutes a shock hazard is often different than what a standard considers a shock hazard. Other conditions may need consideration and you may determine that a shock hazard exists at a lower voltage for your assigned task. This fact emphasizes the need for a proper risk assessment before beginning any task.
The same holds true for the arc-flash hazard. Below 1.2 cal/cm2, there is no arc-flash boundary. There is no requirement to provide arc-flash protection. Does this mean that the employee will not be injured below this minimum energy level? No, a burn injury may still occur at a lower incident energy but the injury is considered to be at an acceptable level. You may want to have all employees wear FR clothing as everyday work gear to protect from energy levels not addressed by the standard.
Your shock and risk assessments must determine if a hazard and risk of injury exists when conducting a task under your specific conditions. Barring any onsite circumstances, below the specified shock and arc-flash thresholds, a hazard may not exist if you follow the minimum requirements. Only you can decide the need for protection at a voltage or incident energy level below that required by the consensus standard. Thankfully, most of you go beyond the standard in this area. However, without attempting to first eliminate the electrical hazards, risk assessments are falling short of what is obligatory under the minimum requirements of the consensus standard.
For more information on 70E, .
Next time: A lockout quiz.