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In the case of a fire involving electrical equipment, the first action must be the
isolation of the power supply so that the circuit is no longer live. This is achieved by
switching off the power supply at the mains isolation switch or at another appropriate
point in the system.

Where it is not possible to switch off the current, the fire must be attacked in a
way that will not cause additional danger. The use of a non-conducting extinguishing
medium, such as carbon dioxide or powder, is necessary.
After extinguishing such a fire careful watch should be kept for renewed
outbreaks until the fault has been rectified. Re-ignition is a particular problem when
carbon dioxide extinguishers are used, although less equipment may be damaged than
is the case when the powder is used.
Finally, the chances of electrical fires occurring are considerably reduced if the
original installation was undertaken by competent electricians working to recognized
standards. It is also important to have a system of regular testing and inspection in
place so that any remedial maintenance can take place.

 Electric arcing

A person who is standing on earth too close to a high voltage conductor may
suffer flash burns as a result of arc formation. Such burns may be extensive and
lower the resistance of the skin so that electric shock may add to the ill effects.
Electric arc faults can cause temporary blindness by burning the retina of the eye
and this may lead to additional secondary hazards. The quantity of electrical energy
is as important as the size of the voltage since the voltage will determine the distance
over which the arc will travel. The risk of arcing can be reduced by the insulation of
live conductors.
Strong electromagnetic fields induce surface charges on people. If these
charges accumulate, skin sensation is affected and spark discharges to earth may
cause localized pain or bruising. Whether prolonged exposure to strong fields has any
other significant effects on health has not been proved. However, the action of an
implanted cardiac pacemaker may be disturbed by the close proximity of its wearer to
a powerful electromagnetic field.

 Static electricity

Static electricity is produced by the build-up of electrons on weak electrical
conductors or insulating materials.
These materials may be gaseous, liquid or solid and may include flammable
liquids, powders, plastic films and granules. The generation of static may be caused
by the rapid separation of highly insulated materials by friction or by transfer from
one highly charged material to another in an electric field by induction (see Figure
14.5).
Discharges of static electricity may be sufficient to cause serious electric shock
and are always a potential source of ignition when flammable liquid, dusts or
powders are present. Flour dust in a mill, for example, has been ignited by static
electricity.

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