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Device Groups for More Safety

Like the devices, gases, vapors, and dust are divided into various groups according to their properties. This division simplifies the right selection of devices for the various gases, vapors, and dusts.

Until the standard EN 60079 0:2009 was introduced, devices permitted in hazardous zones were divided into two groups. Since it came into force, it has been three: groups 1, 2 and 3.

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Principles of Explosion Protection

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Dividing the Device Groups

Group I: Devices for mines susceptible to firedamp.
Group II: Devices for use in area subject to gas explosion (not mines)
Group III: Devices for use in areas with flammable dust (not mines)

The electrical devices of Group II are also subdivided into the groups IIA, IIB, and IIC, depending on the type of atmosphere subject to explosion. This assignment affects the ignition protection types pressure-proof encapsulation (Ex d) and intrinsically safe (Ex i).

Devices for areas with flammable dust are also subdivided into the following groups depending on the type of dust:

Flammable lint
Non-conductive dust
Conductive dust

Device Division

Group	Gas	Maximum experimental safe gap MESG	Minimum ignition current MIC
IIA	Propane	> 0.9 mm	> 0.8
IIB	Ethylene	0.5 … 0.9 mm	0.45 … 0.8
IIC	Hydrogen	< 0.5 mm	< 0.45

Device Groups for More Safety

Principles of Explosion Protection

Dividing the Device Groups

Device Division

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Ex Protection Measures

Zone Divisions

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