An electrical hazard either exists or it does not. Under most circumstances 50 volts or greater is considered to be a shock hazard, and an incident energy of 1.2 cal/cm2 or greater is consider to be a thermal (arc-flash) hazard. When an electrical hazard exists there is always some level of risk of injury, however minimal. The hierarchy of risk controls can be used to affect the hazard or lower the risk. My next few blogs will address the six risk controls in NFPA 70E, Electrical Safety in the Workplace, required to be implemented when the risk assessment reveals that additional protective measures are necessary. The hierarchy of risk controls is:
(3) Engineering controls
(5) Administrative controls
(6) Personal protective equipment (PPE)
Human factors are generally recognized as one of the leading causes of injuries. Employees do not intentionally initiate an electrical incident that results in a “near miss” or an injury. Human error can be either a conscious or inadvertent act. An employee could decide not to follow the standard procedure or not to don the appropriate PPE. They may take their eyes off the task at hand or they may drop a tool. The first three controls are the most effective since they are least affected by human interaction. The last three controls rely on the action of a human and therefore are the least effective. The proper use of the hierarchy is emphasized by the additional 2018 edition requirement that human error be taken into account.
When an electrical hazard is identified and the risk of injury from that hazard is unacceptable, this highest control level must be considered. In the electrical system design and equipment selection phase, it is easier to utilize elimination to limit the risk associated with anticipated justified energized work. During the electrical system design stage, methods should be employed to eliminate the hazard or risk in its entirety. In this first context, elimination is the removal of the electrical hazard so that it does not exist at any time. If there is no hazard, there is no risk of injury. This removes the potential for human error when interacting with the equipment. Elimination is often not an option for installed equipment.
Elimination of the shock hazard at the design stage could be utilizing a 24 Vdc control system rather than a 120 Vac system. This eliminates the shock hazard and greatly minimizes the risk of an electrical injury. Elimination of the risk of injury rather than elimination of the hazard is another possibility. NFPA 70E addresses safe work practices for the employee conducting a task where there is a hazard. The risk of injury is minimized when the employee is not in proximity to the hazard. For example, the use of a remote racking system would not place the employee at risk of injury if an incident were to occur.
As effective as elimination is, it is not foolproof. Equipment could be constructed incorrectly. Incorrect or insufficient maintenance could defeat this control method. Substandard or counterfeit equipment must be avoided. However, elimination of the hazard or risk provides the greatest opportunity for you to protect your employees.
Next up: Substitution and engineering controls.