The answer is Derek Vigstol, Senior Electrical Safety Consultant, e-HazardQuincy, MA.
An electrical risk assessment consists of an electrical shock hazard assessment and an electrical arc hazard assessment.
First, how is risk defined? NFPA 70E 2021, the National Fire Protection Association’s standard for electrical safety in the workplace, addresses risk as the combination of the likelihood of occurrence and the severity of injury or damage to health resulting from an danger. With electricity, there are two main risks: electric shocks and electric arcs. Each hazard requires an independent assessment of each situation and task. Risk assessments aim to answer the following questions:
- Is a danger present?
- Is injury likely to occur?
- How serious is the potential injury?
- How is the risk mitigated in accordance with the hierarchy of risk controls?
Risk of electrocution: An electric shock hazard is defined as a possible source of injury due to contact with/approach to exposed electrical conductors or circuit parts that are energized. 70E also defines the limited approach limit as the distance from exposed and energized parts where a risk of electric shock exists. Answer the following questions: A) Are exposed, live parts (above 50 volts) present and will we cross the limited approach boundary? If so, there is a danger. B) Is injury likely to occur? The restricted approach boundary is where there is an increased likelihood of injury. If this distance is exceeded, injury is likely. Severity is based on voltage. Voltages above 50 can cause fatal or disabling injury. Generally, the higher the voltage, the higher the severity, but many fatalities have resulted from 120 volts (single phase).
Finally, determine an appropriate mitigation strategy based on the hierarchy of risk controls. Consider this a simplified approach for illustrative purposes only: can we create an electrically safe working condition as a result of our hazardous energy control procedure (or lockout/tagout procedure)? If not, can we stay away? If not, can we substitute a different voltage? If not, can we put anything between us and danger? And if none of this is true, we may need to resort to personal protective equipment.
Arc flash hazard: The probability of occurrence is based on the interaction between the employee and the energized equipment, and Table 70E 130.5(C) assists in this determination. The likelihood of injury is centered on being within the arc flash boundary when a hazard exists, and severity is determined either by performing an incident energy analysis or by using the PPE category tables in 70E. However, the last piece remains: can I create an electrically safe working condition? Can I stay away? Can I replace? Can I put something between me and him? Alternatively, PPE can be used to reduce injury severity to survival levels.
Completing both risk assessments is critical to keeping employees safe from electrical hazards. Keep in mind that both should also consider the design of the equipment and the state of maintenance, as these factors can greatly affect the results. However, once we understand the nature of the hazard we are exposed to, we can take effective steps to mitigate the risk and work safely.
Editor’s note: This article represents the independent opinions of the author and should not be construed as an endorsement by the National Security Council.