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SAFETY AND LOSS PREVENTION
Electrical equipment
The sparking of electrical equipment, such as motors, is a major potential source of ignition,
and flame proof equipment is normally specified. Electrically operated instruments, contro-
llers and computer systems are also potential sources of ignition of flammable mixtures.
The use of electrical equipment in hazardous areas is covered by British Standards BS
5345 and BS 5501. The code of practice, BS 5345, Part 1, defines hazardous areas as
those where explosive gas-air mixtures are present, or may be expected to be present,
in quantities such as to require special precautions for the construction and use of
electrical apparatus. Non-hazardous areas are those where explosive gas-air mixtures are
not expected to be present.
Three classifications are defined for hazardous areas:

Zone 0: explosive gas-air mixtures are present continuously or present for long periods.
Specify: intrinsically safe equipment.
Zone 1: explosive gas-air mixtures likely to occur in normal operation.
Specify: intrinsically safe equipment, or flame-proof enclosures: enclosures with pressuriz-
ing and purging.
Zone 3: explosive gas-air mixtures not likely to occur during normal operation, but could
occur for short periods.
Specify: intrinsically safe equipment, or total enclosure, or non-sparking apparatus.

Consult the standards for the full specification before selecting equipment for use in
the designated zones.
The design and specification of intrinsically safe control equipment and systems is
discussed by MacMillan (1998) and Cooper and Jones (1993).

Static electricity
The movement of any non-conducting material, powder, liquid or gas, can generate static
electricity, producing sparks. Precautions must be taken to ensure that all piping is properly
earthed (grounded) and that electrical continuity is maintained around flanges. Escaping
steam, or other vapours and gases, can generate a static charge. Gases escaping from a
ruptured vessel can self-ignite from a static spark. For a review of the dangers of static
electricity in the process industries, see the article by Napier and Russell (1974); and the
books by Pratt (1999) and Britton (1999). A code of practice for the control of static
electricity is given in BS 5938 (1991).

Process flames
Open flames from process furnaces and incinerators are obvious sources of ignition and
must be sited well away from plant containing flammable materials.

Miscellaneous sources
It is the usual practice on plants handling flammable materials to control the entry on to the
site of obvious sources of ignition; such as matches, cigarette lighters and battery-operated