Factors affecting the outcome of electric shock. Occupational Safety and Health

OCCUPATIONAL SAFETY AND HEALTH
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Factors affecting the outcome of electric shock. Occupational Safety and Health

Occupational Safety and Health

Occupational Safety and Health / Legislative basis for labor protection

The effect of current on the human body the nature and consequences of the lesion depends on the following factors:

the magnitude of the current;
duration of current exposure;
frequency and type of current;
applied voltage;
resistance of the human body;
paths for the passage of current through the human body;
the state of human health;
attention factor.

The outcome of electric shock as a whole is determined by the amount of energy "absorbed" by the body of the flow of electric current.

The amount of current flowing through the human body I_Ч, depends on the contact voltage U_ETC and resistance of the human body R_H:

I_Ч = U_ETC / R_Ч.

Recall that the touch voltage is the potential difference between two points of the general circuit of the network (including possible paths for the flow of electric current), in which the human body is included as one of the "conductors". Since the conditional "earth" is always under the feet of a person, they distinguish between "single-point / single-pole" and "two-point / two-pole" touches (and thus including a person in the actual electrical network itself). A one-point touch is much more likely than a two-point touch, but less dangerous than the latter.

It turns out that biological tissue responds to electrical stimulation only at the moment of increasing or decreasing current.

Direct current, as not changing in time in magnitude and voltage, is felt only at the moments of switching on and off from the source. Usually its effect is thermal (with prolonged use). At high voltages, it can cause electrolysis of tissue and blood. According to many researchers, direct current up to 450V is less dangerous than alternating current of the same voltage.

Most researchers have come to the conclusion that alternating current of industrial frequency of 50-60 Hz is the most dangerous for the body.

With an increase in the frequency of the alternating current, the amplitude of the oscillations of the ions decreases, and in this case, there is a lesser violation of the biochemical functions of the cell. At a frequency of about 500 kHz, these changes no longer occur. Here, burns from the thermal effects of current are dangerous for humans.

It turns out that the current in the human body does not necessarily pass along the shortest path. The most dangerous is the passage of current through the respiratory organs and the heart along the longitudinal axis (from the head to the feet).

Part of the total current passing through the heart:

path hand - hand - 3,3% of the total current;
path left arm - legs - 3,7% of the total current;
path right arm - legs - 6,7% of the total current;
path leg - leg - 0,4% of the total current.

The outcome of the lesion when exposed to electric current depends on the mental and physical state of the person.

With diseases of the heart, thyroid gland, etc. a person is subjected to a stronger defeat at lower current values, tk. in this case, the electrical resistance of the human body decreases and the overall resistance of the body to external stimuli decreases. It was noted, for example, that for women the threshold values of currents are approximately 1,5 times lower than for men. This is due to the thinner skin of women.

When using alcoholic beverages, the resistance of the human body falls, the resistance of the human body and attention decrease. The outcome of the defeat is becoming more and more serious.

With collected attention, the resistance of the body increases and the likelihood of damage is somewhat reduced.

Authors: Fainburg G.Z., Ovsyankin A.D., Potemkin V.I.

We recommend interesting articles Section Occupational Safety and Health:

▪ Legal basis for labor protection

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