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EX knowledge

October. 11, 2023

Three Major Factors Causing Explosion


EX knowledge


Classification of Divisions and Zones
ATEX & IECEX ClassificationDefinition of Zone or DivisionNorth American Classification
Zone 0 (gases)An area in which an explosive mixture is continuously present or for long periods or frequently ( ≥ 1000 hours / year).Class I Division 1 (gases)
Zone 20 (dusts)Class II Division 1 (dusts)
Zone 1 (gases)An area in which an explosive mixture is likely to occur during normal oerpations. (10-1000 hours / year).Class I Division 1 (gases)
Zone 21 (dusts)Class II Division 1 (dusts)
Zone 2 (gases)An area in which an explosive mixture is not likely to occur during normal oerpations but may occur for short periods (≤ 10 hours / year).Class I Division 2 (gases)
Zone 22 (dusts)Class II Division 2 (dusts)


Dagerous Level: Zone 0 > Zone 1 > Zone 2;

DivIsion 1 > Division 2


Atmosphere Groups
SubstanceHazard ClassDivision GroupsZone Groups
AcetyleneClass I Flammable GasesGroup AIIC
HydrogenGroup BIIB + H2
EthyleneGroup CIIB
PropaneGroup DIIA
MethaneGroup DIIA6
Combustible Metal DustsClass II Combustible DustsGroup EIIIC
Combustible Carbonaceous DustsGroup FIIIB
Combustible Dust not in Group E or F (Fluor, Grain, Wood Plastics, Chemicals)Group GIIIB
Combustibel Fibers and FlyingsClass III Fibers and FlyingsNot ApplicableIIIA


Dangerous Level: Class I > Cllas II > Calls III


Temperature Classification
Max.Surface TemperatureNEC 500/CECNEC 505/IEC-Group II
450℃ (842°F)T1T1
300℃ (572°F)T2T2
280℃ (536°F)T2A
260℃ (500°F)T2B
230℃ (446°F)T2C
215℃ (419°F)T2D
200℃ (392°F)T3T3
180℃ (356°F)T3A
165℃ (329°F)T3B
160℃ (320°F)T3C
135℃ (275°F)T4T4
120℃ (248°F)T4A
100℃ (212°F)T5T5
85℃ (185°F)T6T6


Equipment Categories & Protection Levels
ATEX CategoryEquipment Protection LevelTypical Equipment Zone Suitability
1GGaZones 0, 1, 2
1DDaZones 20, 21, 22
2GGbZones 1, 2
2DDbZones 21, 22
3GGcZones 2
3DDcZones 22
M1MaVery high level of protection for mines
M2MbHigh level of protection for mines


ATEX Categories VS Zones of Use
Equipment Category ATEX 2014/34/EUZone of Use
Gas,Vapors & MistDust
Category 1Zone 0, 1, 2Zone 20, 21, 22
Category 2Zone 1, 2Zone 21, 22
Category 3Zone 2Zone 22
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