Hazardous areas outside North America are classified by gas groups and zones. Zones are used to define the probability of the presence of flammable materials. Groups classify the exact flammable nature of the material.Protection Types are used to denote the level of safety for the device. Equipment approved receives a temperature code indicating the maximum surface temperature of the equipment.ZonesThe zone defines the probability of hazardous material being present in an ignitable concentration in the surrounding atmosphere.

Zone 0Area in which an explosive gas-air mixture is continuously present or present for long periods.

Zone 1Combustible or conductive dusts are present. Area in which an explosive gas-air mixture is likely to occur for short periods in normal operation.

Zone 2Area in which an explosive gas-air mixture is not likely to occur, and if it occurs it will only exist for a very short time due to an abnormal condition.

Protection TypesDifferent protection techniques are used to address the hazardous zones.

Zone

Ex dFlameproof (Explosion proof) Enclosure1, 2

Ex eIncreased Safety1, 2

Ex iaIntrinsically Safe0, 1, 2

Ex ibIntrinsically Safe1, 2

Ex oOil Immersion2

Ex pPressurized Apparatus (Purged Apparatus)1, 2

Ex qPowder Filling (Sand Filling)2

Ex mEncapsulation1, 2

Ex n or Ex NNon incentive or/and normally no sparking circuits2

Flameproof (Explosion proof) EnclosureAll electrical circuits are enclosed in a house strong enough to contain any explosion or fire that may take place on the inside.Increased SafetyElectrical circuits incorporate special measures to reduce the probability of excessive temperatures and the occurrence of arcs and sparks in normal service.Intrinsically SafetyThe electrical energy available in circuits and equipment, is limited to a level to low to ignite the most easily ignitable mixtures in a hazardous area.Intrinsically safe barriers, as Zener, are installed in the circuit to limit current and voltage in the hazardous areas to avoid sparks or hot spots under fault conditions.

Hazardous Area Types of ProtectionTemperature CodesA mixture of air and hazardous gases may ignite by coming in contact with a hot surface. An ignition depends on surface area, temperature and the concentration of the gas.Certified equipment are tested for maximum temperature ratings by approval agencies. Equipment for Group II receives a temperature code indicating the maximum surface temperature.Temperature CodeoFoC

T1842450

T2572300

T3392200

T4275135

T5212100

T618585

The coding is based on a 104 oF (40 oC) ambient temperature.The automatic ignition temperature can be found in IEC 79-4. Critical Temperature Parameters For Dust ExplosionsGroupsElectrical equipment is divided into two groups where Group I covers equipment used in mines and Group II covers all other applications. Group II is subdivided into three subgroups where the specific hazardous materials within each group can be found in CENELEC EN 50014.Group IFor application in below ground installations (mines) where methane (firedamp) and coal dust may be present.

Group IIAFor application in above ground installation where hazards due to propane may exist.

Group IIBFor application in above ground installations where hazards due to ethylene may exist.

Group IICFor application in above ground installations where hazards due to hydrogen or acetylene may exist.