Gas and Dust Groups

ATEX, IECEx and US / Canada zones system US / Canada class / division system
Gas / dust group Typical Substances Gas / dust group       Typical Substances
IIC Acetylene
Class I, Group A Acetylene
IIB + H2
Hydrogen
Class I, Group B Hydrogen
IIB
Ethylene
Class I, Group C
Ethylene
IIA Propane Class I, Group D Propane
IIIC
Conductive dust
Class II, Group E
Combustible metal dust
IIIB
Non-conductive dust
Class II, Group F
Combustible carbonaceous dust
Class II, Group G  Combustible dusts not in group E or F
IIIA Combustible flyings Class III Combustible fibres and flyings

Temperature Classifications

Group II & III Class I, II & III
Max. surface temp. of equipment (°C) Temperature 
class
Ignition temperature of gas / dust (°C) Max. surface temp. of equipment (°C)
Temperature class 
Ignition temperature of gas / dust (°C)
400 T1 >450 450 T1 >450
300 T2 >300-450 300 T2 >300-450



280 T2A >280-300



260 T2B >260-280



230 T2C >230-260



215 T2D >215-230
200 T3 >200-300 200 T3 >200-215



180 T3A >180-200



165 T3B >165-180



160 T3C >160-165
135 T4 >135-200 135 T4 >135-160



120 T4A >120-135
100 T5 >100-135 100 T5 >100-120
85 T6 >85-100 85 T6 >85-100


Note: For Group I mining applications, apparatus has a rigid 150°C coal dust and 450°C methane limits rather than T classes.