Lethal Electricity Explained

While searching for information on the lethal potential of electrical shock I came across an article by Zach Eveland that provides a clear and simple explanation.

Play safe kiddies.

“…it’s the current that kills, in most cases by interfering with the normal operation of the heart. Be careful though – with the right conditions, shocks way below 1 Amp can be lethal. In designs where you are trying to prevent electrocution, 5 milliamps is considered the upper limit of safe operation. Notice that that’s 5 MILLIamps – barely enough to light an LED.

“The thing to measure is how much current is flowing through the heart and you have to assume the worst case; that someone is holding positive with one hand and negative with the other, letting the electricity go right through their chest and heart. Body and skin resistance, hand-to-hand, varies but 10 kohm is a safe figure to work with (though it can be even less with wet hands and can go much higher, up to hundreds of kohms).

“Here’s an example for figuring current: with a 9V battery and 10 kohm of body resistance, if I hold positive with one hand and negative with the other, the current through my heart is equal to 9V divided by 10 kohm or 0.9 mA – in the safe range.

“One more warning; be careful with this – keep your hands dry, don’t stand in water, have somebody around when you’re testing, don’t shock people with weak hearts, etc.

“In general, [to produce a safe shock, something I don’t recommend – tigoe] you want a high-voltage, very low-current source of electricity, ideally DC since AC voltages are more likely to interfere with heart rhythm. A good value would be several hundred volts at way less than 5 mA. The best design would limit the amount of current to a safe level. Luckily, there are pre-built devices that do this (though I sure as hell won’t vouch for any of them): search eBay for “nerve stimulator” or “TENS”. Other options would be the peizo igniter from a cigarette or BBQ lighter or the flash unit from a disposable camera.

“Again, be safe and smart, and good luck.”
-Zach E