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conductor, and if the chest is in the current path, respiratory movement may be
prevented causing asphyxia.
Current passing through the chest may also cause fibrillation of the heart
(vibration of the heart muscle) and disrupt the normal rhythm of the heart, though this

is likely only within a particular range of currents.
The shock can also cause the heart to stop completely (cardiac arrest) and this
will lead to the cessation of breathing. Current passing through the respiratory centre
of the brain may cause respiratory arrest that does not quickly respond to the breaking
of the electrical contact.
These effects on the heart and respiratory system can be caused by currents as
low as 25 mA. It is not possible to be precise on the threshold current because it is
dependent on the environmental conditions at the time, as well as the age, sex, body
weight and health of the person (Figure 14.1).
Burns of the skin occurs at the point of electrical contact due to the high
resistance of the skin. These burns may be deep, slow to heal and often leave
permanent scars. Burns may also occur inside the body along the path of the electric
current causing damage to muscle tissue and blood cells. Thermal burns from the heat
are radiated from an electric arc flash.
Ultraviolet (UV) and infrared (IR) light emitted from the arc flash can also
cause damage to the eyes.

Figure 14.1 – Electrical shock

 Treatment of electric shock and burns

There are many excellent posters available which illustrate a first-aid procedure
for treating electric shock and such posters should be positioned close to electrical
junction boxes or isolation switches.

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