Contact with Energized Sources
The major hazards regarding contact with energized sources are electrical shock and burns.
Electrical shock occurs when the body becomes part of the electric circuit. This occurs when an individual comes in contact with both wires of an electrical circuit (one wire of an energized circuit and the ground, or a metallic part that has become energized by contact with an electrical conductor).
The severity and effects of an electrical shock depend on a number of factors, such as:
- the pathway through the body,
- the amount of current,
- the duration of the exposure, and
- whether the skin is wet or dry.
Water is a great conductor of electricity, allowing current to flow more easily in wet conditions and through wet skin. The table below discusses the effects of electrical shock.
Electrical burns can be arc burns, thermal contact burns, or a combination of burns. Electrical burns are among the most serious burns and require immediate medical attention. They occur when an electric current flows through tissue or bone, generating heat that causes tissue damage. The body cannot dissipate the heat generated by current flowing through the resistance of the tissue. Therefore, burns occur.
| 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! |
*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.
(1000 milliamperes = 1 amp; therefore, 15,000 milliamperes = 15 amp circuit)
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7-4. What type of burns are the most serious and require immediate medical attention?
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