Five common causes of electrical fatalities
Almost all American workers are exposed to electrical energy at sometime during their work day, and the same electrical hazards can affect workers in different industries. Based on the analysis of these cases, NIOSH identified five case scenarios that describe the incidents resulting in 244 fatalities:
(1) direct worker contact with an energized powerline (28%);
(2) direct worker contact with energized equipment (21%);
(3) boomed vehicle contact with an energized powerline (18%);
(4) improperly installed or damaged equipment (17%);
(5) conductive equipment contact with an energized powerline (16%).
Workers in various occupations such as sign technicians, tree trimmers, utility line workers, and telecommunication workers are often exposed to overhead powerlines. These exposures can be greatly reduced by isolating or insulating the energy source from the worker. This can be accomplished by erecting a physical barrier, by insulating the powerline, or by following required clearance distances. More than once during NIOSH fatality investigations, co-workers interviewed did not know the powerlines posed a hazard, i.e., they thought the powerlines were insulated.
Direct worker contact with energized equipment can occur in a variety of ways. Maintenance technicians might inadvertently contact overhead crane runway conductors. Electricians or technicians troubleshooting or testing electric circuitry might contact an energized circuit. Maintenance workers may fail to replace an isolating plate covering electrical conductors, exposing passing workers. Compliance with the applicable articles of the National Electrical Code and lockout/tagout procedures established by OSHA could eliminate the potential for such contact, thereby reducing the risk of electrocution.
Workers guiding suspended loads, or standing against or near a crane or other boomed vehicle—such as a concrete pumping truck, or derrick truck—whose boom contacts a powerline are in danger of electrocution. The risk of electrocution could be reduced if OSHA regulations regarding clearance distances [(29 CFR 1926.550 (a)(15)] are observed, or if the required lookout person [29 CFR 1926.550 (a)(15)(iv)] is utilized.
Improperly installed or damaged equipment can be responsible for occupational electrocutions in a variety of ways. The most frequently cited OSHA electrical regulation is improper grounding of equipment or electrical circuitry. If the frame of a piece of electrical equipment or machinery does not have a grounding conductor attaching the frame to ground, as required to divert dangerous fault current to ground, and an electrical fault occurs, anyone touching that frame and any other object at ground potential would receive an electrical shock. Should a fault occur with a grounding conductor present, the circuit would open or trip as an alert that a problem existed, except in high-resistance grounding applications. Damaged guards can expose workers to energized conductors in proximity to their work areas. Additionally, damaged extension cords or extension cords with their ground prong removed can expose workers to the danger of electrocution. Failure to maintain a continuous path to ground can expose entire electrical systems to damage and can expose the structures within which they are housed and workers within these structures to electrical and fire hazards.
For example, many electrical systems are installed in a manner that allows a structure’s water pipes or other conductive conduit to serve as a continuous path to ground in compliance with the NEC. However, NIOSH fatality investigations have identified cases of electrocution or fire as a result of an interruption in a continuous path to ground. During renovation or repair activities, conductive components may be replaced by nonconductive components such as PVC pipe, which will interrupt the path to ground.
This may result in fire due to the intense overheating of components of the electrical system. Additionally, workers contacting improperly grounded components while being at ground potential would be exposed to electric shock.
The task of positioning or repositioning conductive equipment may place more than one worker at risk. The weight of mobile scaffolding, grain augers, or aluminum extension ladders equipped with pendant-operated lifts often requires more than one worker for positioning or repositioning, resulting in multiple electrocutions if contact with an overhead powerline occurs. Using a lookout person, observing required clearance distances, or lowering this equipment before transport would greatly reduce worker exposure to any potential electrical hazards present.
Fatality data help to illustrate the magnitude of the electrocution problem nationally and allow a comparison of the potential risks in various industries. The information from NIOSH investigations allows for the identification of more detailed information on electrocution hazards, such as contact with overhead powerlines, contact with exposed conductors, inadequate personal protective equipment, and nonexistent lockout/tagout procedures, or other measures necessary for working around energized conductors and equipment.
Fatality reports and death certificates identified many of the same hazards for fatal electrocutions.
The largest number of deaths were in Construction, Transportation/Communication/Public Utilities, and Manufacturing, while the highest fatality rates were in the Construction and Mining industries.
Linemen were involved in the largest number of electrocutions.
Direct worker contact with an energized powerline caused the largest number of electrocution deaths.
Almost all of the incidents investigated by NIOSH involved alternating current. More than half of these incidents involved voltages of more than 600 volts. Of the 147 higher-voltage electrocutions, over two-thirds involved distribution voltages (7,200-13,800 volts).
While progress has been made in reducing the number of work-related electrocutions, (50% decrease from 1980-1992), additional efforts are needed if we are to continue progress towards preventing deaths due to electrocution, according to NIOSH.
It’s clear the positive and life-saving role training can play in preventing these tragedies.