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Dangerous areas and zones

Dangerous areas include any area in which explosive atmospheres may occur under specific conditions. An explosive atmosphere is a mixture of air and combustible gases, vapours, fumes or dust under atmospheric conditions where combustion expands itself (explosion) after ignition. Only local authorities can classify hazardous areas. The user shall classify the hazardous areas as indicated in the European directive 1999/92/EC under his own responsibility. International standards IEC 61241-10 provide instructions on how to classify the hazardous areas in relation to the chemical nature, to the physical characteristics and to the amount of substances used and based on the frequency and period of time in which an explosive mix may develop.

Zones susceptible to gas

When the hazard is due to the presence of gas, vapours or mists of flammable substances, the European directive 1999/92/EC envisages a classification in three zones defined as follows:
Zone 0 - Areas constantly susceptible to an explosive atmosphere, or for long periods of time. Power equipment with double insulation must be installed in this area.
Zone 1 - Areas where an explosive atmosphere is likely to develop during normal conditions. Flameproof electric motors or motors with added protection means can be installed in this zone (for the latter, restrictions by the standards apply).
Zone 2 - Areas rarely susceptible to an explosive atmosphere and for a short period of time. Flameproof motors or motors with added protection can be installed in this zone, as well as non-sparking motors.

Zones susceptible to combustible dust

When the hazard is due to the presence of combustible dust, the European directive 1999/92/EC envisages a classification in three zones defined as follows:
Zone 20 - Areas constantly susceptible to an explosive atmosphere, or for long periods of time. Power apparatus cannot be installed in this zone. Zone 21 - Areas where an explosive atmosphere is likely to develop during normal conditions. Electric motors certified in compliance with the ATEX directive with IP6X protection rating can be installed in this zone.
Zone 22 - Areas rarely susceptible to an explosive atmosphere, and only for a short period of time. In the presence of conductive dust, electric motors certified in compliance with the ATEX directive with protection rating IP6x can be installed in this zone, whereas in the presence of non conductive dust, motors with protection rating IP5x and a declaration of conformity issued by the manufacturer can be installed.

DANGEROUS AREAS CLASSIFIED INTO ZONES
Usage area
in the presence of
GAS
Usage area
in the presence of
COMBUSTIBLE DUSTS
Hazardous level
of the operational
ZONE
Zone 0Zone 20Explosive atmosphere
ALWAYS PRESENT
Zone 1Zone 21PROBABLE
explosive atmosphere
Zone 2Zone 22Explosive atmosphere
UNLIKELY