This has been a discussion that occurs at work sites around the country (or for that matter around the world) with folks teasing others about not being "man enough" to work on live equipment. There is a name for these types of folks and it is not "macho": it is "injured" or "dead."
At what level can current harm? If you look at the OSHA e-Tools you will find the following chart:
|
Current level
(in milliamperes)
|
Probable effect on human body
|
|
1 mA
|
Perception level. Slight tingling sensation. Still dangerous under certain conditions.
|
|
5 mA
|
Slight shock felt; not painful but disturbing. Average individual can let go. However, strong involuntary reactions to shocks in this range may lead to injuries.
|
|
6-30 mA
|
Painful shock, muscular control is lost. This is called the freezing current or "let-go" range.
|
|
50-150 mA
|
Extreme pain, respiratory arrest, severe muscular contractions. Individual cannot let go. Death is possible.
|
|
1000-4300 mA
|
Ventricular fibrillation (the rhythmic pumping action of the heart ceases.) Muscular contraction and nerve damage occur. Death is most likely.
|
|
10,000 mA
|
Cardiac arrest, severe burns and probable death.
|
|
|
Wet conditions are common during low-voltage electrocutions. Under dry conditions, human skin is very resistant. Wet skin dramatically drops the body's resistance.
|
|
Dry Conditions: Current = Volts/Ohms = 120/100,000 = 1mA
a barely perceptible level of current
Wet conditions: Current = Volts/Ohms = 120/1,000 = 120mA
sufficient current to cause ventricular fibrillation
|
As you can see, it does not take much to lead to severe injuries and that a difference of less than 100 milliamperes exists between a current that is barely perceptible and one that can kill.
So I guess the rule should be "work live and you might die. There is nothing "macho" about being dead: ask your family. Shop now for arc flash clothing compliant to NFPA 70: Standard for Electrical Safety in the Workplace.
Article generously provided by James Norton, President of the JHN Group. He can be contacted regarding Machine Safety Consulting at jamesnorton@jhngroup.com or online at www.jhngroup.com.