What is Electric shock and How to Prevent it?

Electric shock occurs when a person becomes part of the electrical circuit, as shown in picture . 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.

What is Protective electrical bonding to earth?

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.