The human shock limit isn't a single, fixed number, but rather a range of electrical current that can cause a variety of dangerous effects, including death. A current as low as 1/10 of an amp (100 milliamperes) passing through the body for just 2 seconds can be fatal.
Factors Influencing the Shock Limit
Several factors determine the severity of an electric shock, including:
- Current (Amperes): This is the most critical factor. Higher current levels cause more severe injuries.
- Voltage: Higher voltages can drive more current through the body.
- Path: The path electricity takes through the body significantly impacts the outcome. If it passes through the heart or brain, the consequences are much more severe.
- Duration: The longer the exposure, the more damaging the shock.
- Frequency: Alternating current (AC) at certain frequencies is more dangerous than direct current (DC) at the same voltage and amperage.
- Individual Factors: Resistance varies based on skin dryness, overall health, and other individual characteristics. Dry skin offers more resistance than wet skin.
Effects of Different Current Levels (AC)
The following table summarizes the approximate effects of different levels of alternating current (AC) on the human body. These values can vary greatly between individuals.
| Current (mA) | Effect |
|---|---|
| 1 | Perception – Faint tingle |
| 5 | Slight shock felt; disturbing but not painful; most individuals can let go. |
| 6-30 | Painful shock, muscular control is lost. This is the "let-go" range. |
| 50-150 | Extreme pain, respiratory arrest, severe muscular contractions. |
| 100-300 | Ventricular fibrillation (irregular heartbeat), likely fatal. |
| 500+ | Severe burns, cardiac arrest. |
Note: mA = milliamperes (1/1000 of an amp)
"Let-Go" Current
The "let-go" current is a crucial concept. It refers to the maximum current a person can withstand and still voluntarily control their muscles to release the source of the electricity. This value is typically less than 10 milliamperes (mA). Once this level is exceeded, muscle contractions can prevent a person from letting go, leading to prolonged exposure and increased risk.
Preventing Electrical Shock
- Use Ground Fault Circuit Interrupters (GFCIs): These devices quickly cut off power when a ground fault is detected, significantly reducing the risk of shock.
- Inspect Electrical Cords and Equipment Regularly: Look for damaged insulation or frayed wires.
- Never Use Electrical Appliances Near Water: Water significantly reduces the body's resistance and increases the risk of electrocution.
- Turn Off Power Before Working on Electrical Circuits: Always disconnect power at the breaker box before performing any electrical work.
- Use Appropriate Personal Protective Equipment (PPE): When working with electricity, wear insulated gloves, safety glasses, and other appropriate PPE.
In conclusion, the human shock limit is highly variable and depends on numerous factors, but currents as low as 100 mA can be fatal. Awareness and preventative measures are critical to avoiding electrical injuries.
