Low Voltage Does Not Mean Low Hazard
The table below illustrates the general relationship between the amount of current and the corresponding reaction when the current flows from the hand to the foot for a duration of just 1 second.
Effects of Electrical Current* on the Body
| Current | Reaction |
|---|---|
| 1 milliamp | Just a faint tingle. |
| 5 milliamps | Slight shock felt. Disturbing, but not painful. Most people can "let go." However, strong involuntary movements can cause injuries. |
| 6-25 milliamps (women)** 9-30 milliamps (men) |
Painful shock. Muscular control is lost. This is the range where "freezing currents" start. It may not be possible to "let go." |
| 50-150 milliamps | Extremely painful shock, respiratory arrest (breathing stops), severe muscle contractions. Flexor muscles may cause holding on; extensor muscles may cause intense pushing away. Heart fibrillation possible. Death is possible. |
| 1,000-4,300 milliamps (1-4.3 amps) | Rhythmic pumping action of the heart ceases. Muscular contraction and nerve damage occur; death likely. |
| 10,000 milliamps (10 amps) | Cardiac arrest and severe burns occur. Death is probable. |
| 15,000 milliamps (15 amps) | Lowest overcurrent at which a typical fuse or circuit breaker opens a circuit! |
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* Effects are for voltages less than about 600 volts. Higher voltages also cause severe burns. ** Differences in muscle and fat content affect the severity of shock. |
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Real-Life Accidents
At 3:45 p.m. on February 18, 2022, an employee was installing an electrical box in the ceiling to power a new overhead projector and did not lockout the breaker box. The employee suffered electrical shock and was hospitalized.
At 2:45 a.m. on August 23, 2022, an employee was working as a roofer for a roofing contractor installing a metal roof on a residential home. The employee climbed a secured ladder while carrying a 10-foot piece of metal trim. A coworker called out to the worker on the ladder causing him to turn around. At this point, the metal trim contacted a live electrical line causing him to fall approximately 18 feet to the ground. EMS transported the employee to the hospital, where he died.
Knowledge Check Choose the best answer for the question.
1-5. What minimum level of current can cause an extremely painful shock, respiratory arrest (breathing stops), and severe muscle contractions?
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