Temperature Classification

According to the IECEx, ATEX and CSA certification regulations, the surface temperature of any equipment used in hazardous areas cannot exceed 80 % of the auto ignition temperature of the gas in question. The auto ignition temperature is the temperature where a gas, liquid, vapor or hazardous atmosphere will auto ignite, without any external ignition or heat source. These temperatures have been tested in various laboratories, and for the most common gas types the temperatures and classes are as follows:

Gas Temperature
Methane 580 °C
Hydrogen 560 °C
Propane 493 °C
Ethylene 425 °C
Acetylene 305 °C
Naphtha 290 °C
Carbon disulfide 102 °C
(IEC) °C
Germany °C
Continuous – Short Time
T1 – 450 G1: 360 – 400
T2 – 300 G2: 240 – 270
T3 – 200 G3: 160 – 180
T4 – 135 G4: 110 – 125
T5 – 100 G5: 80 – 90
T6 – 85

Normally, mobile devices for hazardous areas are certified for T4, which covers most use cases. A mobile device is used by people, and therefore 135 degrees C is more than enough for most use cases. T4 is accepted for most hydrocarbon based hazardous areas and gas types. Sources: BARTEC TECHNOR, Wikipedia and IECEx websites.