Introduction to the principles of explosion
protected electrical equipment
IEC 60079-0 to IEC 60079-18
For hazardous areas, it is very important that the product is designed for use in the
actual area, and that operation and maintenance are according to the requirements.
The norms for hazardous areas are not the same for all over the world, but during
the last years, the world wide harmonizing work have had much focus, and the
IEC Ex certification is being ratified by more and more countries. For Europe, the
ATEX directives for equipment (94/9/EC) and worker protection (1999/92/EC) in
potentially explosive atmospheres become mandatory from 1st July 2003.
This means that all products delivered for installation in hazardous area in buildings
and fixed installations in Europe from that date have to be certified according to the
The ATEX directives are covering both electrical and non-electrical equipment, and for
the first time, mechanical equipment falls under this type of legislation.Classification of Zones
The hazardous areas have to be classified in Zones:ZONE 0
is a place where an explosive atmosphere consisting of a mixture of air
with any combination of flammable gas, vapour or mist is present continously, frequently
or for long periods.ZONE 1
is a place where an explosive atmosphere consisting of a mixture of air with any combination of flammable gas, vapour or mist is present only occasionally during normal operation.ZONE 2
is a place where an explosive atmosphere consisting of a mixture of air with any combination of flammable gas, vapour or mist is not likely to occur in normal
operation, but if it occurs, will persist for a short period of time.
For explosive atmospheres due to combustible dust in air, a similaire classification exists, with the zones numbered Zone 20, Zone 21 and Zone 22.Category groups
Electrical equipment has to be classified in two different category groups:Group I
Electrical equipment for miningGroup II
Electrical equipment for all remaining hazardous areasEquipment group
For the different areas, the equipment has
to be classifiedGroup II. For gas and dust:
Zone 0/20 Equipment 1G/1D
Zone 1/21 Equipment 2G/2D
Zone 2/22 Equipment 3G/3DGroup I. For mining:
Dust M2 or M1European Standard
European coding marking standard for products designed for use in hazardous areas: Ex
is the coding for products confirming to IEC standard
If the product confirms to the harmonised European Standards which has been notified by EU for the ATEX directive, the product will also carry the hexagon Exsymbol.
Directive 1999/92/EC do also have requirement that areas in which explosive atmospheres can occur must have warning signs.