Brochure/Catalogue

The basics of explosion protection
Explosive atmosphere
An explosive atmosphere is created by an air mixture of
ammable gases, vapours, mist or dust. When an ignition
occurs in an explosive atmosphere, the reaction continues
independently in these atmospheric conditions. Such
atmospheric conditions are in the range from 0.8 to 1.1
bar absolute pressure and –20 °C to +60 °C mixture
temperature.
This specication is the basis for the European directives and
their derived regulations. The danger of an explosion exists
when the following conditions are met simultaneously:
• The proportion of ammable substances is so high that
an explosive mix can occur
• An ignition source capable of igniting the mixture is
located in the same room
• There is sufcient oxygen available for an explosion
Ignition sources that can trigger an explosion
include:
• Electrical sparks and arcs, for example:
– During the opening and closing of circuits
– Discharges from charged equipment parts
– At the switching mechanism in switching equipment
– From damaged cables and wires
– Short circuits
– Electrical compensating currents
• Sparks created mechanically from friction, impact or
grinding motions
• A hot surface, such as live wires in junction boxes, motor
windings, heating conductors, bearings, shaft bushings
• Electrostatic charges resulting from cutting processes
where at least one chargeable substance is involved
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ATEX directive 2014/30/EU
According to ATEX Directive 2014/30/EU, the employer
must provide the appropriate measures to protect the safety
and health of its employers. One such measure is dividing
a hazardous area into zones where there is a risk that an
explosive atmosphere may be present.
Zone division
Flammable gases, vapours and mist
Zone 0
A zone where there is a constant and long-term occurrence of an explosive atmosphere
(consisting of air mixed with ammable gases, vapours or mist).
Zone 1
A zone where, during normal operations, an explosive atmosphere (consisting of air
mixed with ammable gases, vapours or mist) occurs occasionally.
Zone 2
A zone where, during normal operations, an explosive atmosphere (consisting of air
mixed with ammable gas, vapour or mist) is not anticipated, but could rarely occur for
only a short period.
see EN60079-14:2008
Zone division
Flammable dusts
Zone 20
A zone where, during normal operations, an explosive atmosphere (consisting of a
ammable dust in the air) occurs often or for longer periods.
Zone 21
A zone where, during normal operations, an explosive atmosphere (consisting of a
ammable dust in the air) occurs occasionally.
Zone 22
A zone where, during normal operations, an explosive atmosphere (ammable dust in the
air) is not anticipated, but could possibly occur for only a short period.
see EN60079-14:2008
The ATEX device category is used to select the proper EX
devices for a particular zone (refer to the ATEX Directive
2014/30/EU, on pages 31–33). Since there are no device
categories in the IECEx denition, the equipment protection
level (EPL) is used to pick the suitable devices. These
equipment protection levels assess the risk of internal
ignition within a device, whereby the type of internal ignition
protection applied is not a factor.
The basics of explosion protection
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