This seems to be a rather morbid subject, but here is my theory. Human skin is somewhat of an insulator. Once this barrier is broken down very low voltages can cause lethal currents. When people are in a tub the skin barrier is broken down (through body cavities?) and the body becomes a low enough impedance (parallel paths) relative to the water that significant current can flow. As far as an ungrounded drain there could have been other paths to ground through splashed water or leaks. A GFI should have prevented lethal currents, unless it was wired wrong or defective. I my experience, incidents like this are usually a series of improbable events that occur at the same time.
Darrell Locke Advanced Input Devices ---------- From: [email protected] To: IEEE Product Safety Technical Committee - Subject: GFIs, Hairdryers, and Bathtubs ... List-Post: [email protected] Date: Wednesday, August 13, 1997 9:51AM Recently somewhere back in the news (couple of weeks ago), two children died when one of them used a hairdryer in the tub. A discussion this accident with some lead me to a counter-intuitive result from my experience in product safety. ************************************************** Given Situation #1: 1. Person in a tub of water sitting at the opposite end of the tub than the drain. 2. The tub is ungrounded with water in it. Ungrounded meaning that the drain is plastic piping. 3. A 2-wire hair dryer (either On or OFF) is dropped into the water at the drain end of the tub. The person in the tub is neither in contact with the hairdryer, not anything that would be grounded. The hairdryer has a plastic case. Result: 1. Since there is no path to ground from the hairdryer through the person in the tub to ground, no current should flow *thru* the person in the tub. The person is in no harm. 2. Since no current is flowing through ground, the GFI won't trip. If the water allows sufficient current to flow by shorting between the HOT and NEUTRAL in the hairdryer, the breaker will trip. ************************************************** Given Situation #2: Same as situation #1 except that the drain is now a grounded metal pipe. Is there a sufficient parallel path to be lethal to the person in the tub? Seems as though the parallel path for the hairdryer is straight to the drain. Result: 1. Person is still unharmed. 2. GFI trips. ************************************************** Are my conclusions correct? Is the only time one can be electrocuted in a tub when they are in contact with a ground and holding the hairdryer? Is a person really killed in a tub with hairdryer by drowning rather than electrocution? I'm beginning to doubt that I know exactly how a person is killed in a tub with a hairdryer. Or, am I making this way more complicated than it is? Comments?
