The danger of receiving electric shock is increased when working around water. To receive an electrical shock, a person must be part of a closed circuit in which current can flow through them. Just how badly a person is affected by electric shock depends on the following:

1. The path the current takes through the body. The chest and head are the most vulnerable areas. All personnel should wear rubber lineman's gloves and a safety helmet.
2. The time spent in the circuit. The sooner the circuit is interrupted the better.
3. The person's age, size, and health. The greatest danger is to a person with a prior heart ailment.
4. The amount of current that flows through the body. When the body is submerged in water this becomes a complex situation involving many variables and very little data is available.
5. The type of current, AC or DC. Humans are three times more likely to be electrocuted by AC current than by DC. For this reason Smith-Root barrier and guidance systems only use DC current.
6. Whether the current flow is continuous or pulsed. UL Laboratories found that short pulses are much less likely to be lethal, see figure below. Smith-Root barrier and guidance systems use a pulse of much shorter duration than that of a typical Ground Fault Interrupter Circuit.

Effects of an electrical pulse on humans passed through the chest. Adapted from the Handbook of Electronic Safety Procedures 1982.