Human Thresholds of Electric Shock at Power Transmission Frequencies

Abstract

Reliable quantitative data about electric shock to humans at power transmission frequencies are available for three physiological responses to electrical stimulation: perception, uncontrollable muscular contraction, and death. Some humans can perceive less than 0.5 rna of 50 to 60 Hertz current, depending upon the type of hand contact made with an electrically energized circuit. Most adult male workers should be able to release 9 rna of 50 to 60 Hz current. A safety threshold of 5 ma, recommended for the general population including children, is based upon the conclusion that current in excess of release threshold should be regarded as hazardous and potentially lethal. Relevant threshold conditions inctude body size, current pathway, contact duration, and total resistance. Voltages calculated from reliable experimental data on effective currents and expected resistances are lower than voltages generally recommended to be safe.