Electricity travels in closed circuits, and its normal route is through a conductor. Electric shock occurs when the body becomes a part of the electric circuit. The current must enter the body at one point and leave at another. Electric shock normally occurs in one of three ways. Individuals, while in contact with the ground, must come in contact with:
- Both wires of the electric circuit,
- One wire of an energized circuit and the ground, or
- A metallic part that has become “hot” by contact with an energized conductor.
- Amount of current flowing through the body (measured in amperes),
- Path of the current through the body, and
- Length of time the body is in the circuit.
LOW VOLTAGE DOES NOT IMPLY LOW HAZARD!
Perception level. Just a faint tingle.
Slight shock felt; not painful but disturbing.
Average individual can let go. However, strong involuntary reactions to shocks in this range can lead to injuries.
6-25 Milliamperes (women)
Painful shock, muscular control is lost.
9-30 Milliamperes (men)
This is called the freezing current or “let-go” range.
Extreme pain, respiratory arrest, severe muscular contractions[*]. Individual cannot let go. Death is possible.
Ventricular fibrillation. (The rhythmic pumping action of the heart ceases.)
Muscular contraction and nerve damage occur. Death is most likely.
Cardiac arrest, severe burns and probable death.
[*]If the extensor muscles are excited by the electric shock, the person may be thrown away from the circuit. Source: W.B. Kouwenhoven, Human Safety and Electric Shock, Electrical Safety Practices, Monograph, 112, Instrument Society of America, p. 93. (Papers delivered at the third presentation of the Electrical Safety Course given in Wilmington, DE, in November 1968.)