Electric shock occurs when a person becomes part of the electrical circuit,
as shown in Fig. 1.13 . The level or intensity of the shock will depend
upon many factors, such as age, fi tness and the circumstances in which
the shock is received. The lethal level is approximately 50 mA, above which
muscles contract, the heart fl utters and breathing stops. A shock above the
50 mA level is therefore fatal unless the person is quickly separated from
the supply. Below 50 mA only an unpleasant tingling sensation may be
experienced or you may be thrown across a room, roof or ladder, but the
resulting fall may lead to serious injury.
How to prevent people receiving an electric shock?
To prevent people receiving an electric shock accidentally, all circuits must
contain protective devices. All exposed metal must be earthed; fuses and
miniature circuit breakers (MCBs) are designed to trip under fault conditions
and residual current devices (RCDs) are designed to trip below the
fatal level as described in Chapter 4.
Construction workers and particularly electricians do receive electric
shocks, usually as a result of carelessness or unforeseen circumstances.
When this happens it is necessary to act quickly to prevent the electric
shock becoming fatal. Actions to be taken upon fi nding a workmate receiving
an electric shock are as follows:
● Switch off the supply if possible.
● Alternatively, remove the person from the supply without touching
him , e.g. push him off with a piece of wood, pull him off with a scarf,
dry towel or coat.
● If breathing or heart has stopped, immediately call professional help
by dialling 999 or 112 and asking for the ambulance service. Give
precise directions to the scene of the accident. The casualty stands
the best chance of survival if the emergency services can get a rapid
response paramedic team quickly to the scene. They have extensive
training and will have specialist equipment with them.
● Only then should you apply resuscitation or cardiac massage until
the patient recovers, or help arrives.
● Treat for shock.
as shown in Fig. 1.13 . The level or intensity of the shock will depend
upon many factors, such as age, fi tness and the circumstances in which
the shock is received. The lethal level is approximately 50 mA, above which
muscles contract, the heart fl utters and breathing stops. A shock above the
50 mA level is therefore fatal unless the person is quickly separated from
the supply. Below 50 mA only an unpleasant tingling sensation may be
experienced or you may be thrown across a room, roof or ladder, but the
resulting fall may lead to serious injury.
How to prevent people receiving an electric shock?
To prevent people receiving an electric shock accidentally, all circuits must
contain protective devices. All exposed metal must be earthed; fuses and
miniature circuit breakers (MCBs) are designed to trip under fault conditions
and residual current devices (RCDs) are designed to trip below the
fatal level as described in Chapter 4.
Construction workers and particularly electricians do receive electric
shocks, usually as a result of carelessness or unforeseen circumstances.
When this happens it is necessary to act quickly to prevent the electric
shock becoming fatal. Actions to be taken upon fi nding a workmate receiving
an electric shock are as follows:
● Switch off the supply if possible.
● Alternatively, remove the person from the supply without touching
him , e.g. push him off with a piece of wood, pull him off with a scarf,
dry towel or coat.
● If breathing or heart has stopped, immediately call professional help
by dialling 999 or 112 and asking for the ambulance service. Give
precise directions to the scene of the accident. The casualty stands
the best chance of survival if the emergency services can get a rapid
response paramedic team quickly to the scene. They have extensive
training and will have specialist equipment with them.
● Only then should you apply resuscitation or cardiac massage until
the patient recovers, or help arrives.
● Treat for shock.
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