| 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 |
| 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.
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