Temperature Codes & Auto-Ignition Temperature (AIT)
- Details
- Category: Hazardous Locations
AIT (Auto-Ignition Temperature) is the temperature at which a gas, vapour or dust will ignite spontaneously without any other sources of ignition. Years ago, the IEC recognized that there was no relation between the gas, vapour and dust groupings, and the AITs of the various compounds. As such, temperature codes were established for equipment used in hazardous locations, and adopted by CEC and NEC.
| IEC and North American Temperature Codes | ||
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| IEC Temperature Codes (European Standard) |
Temperature, °C | North American Temperature Codes |
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| T1 | 450 | T1 |
| T2 - - - - |
300 280 260 230 215 |
T2 T2A T2B T2C T2D |
| T3 - - - |
200 180 165 160 |
T3 T3A T3B T3C |
| T4 - |
135 120 |
T4 T4A |
| T5 | 100 | T5 |
| T6 | 85 | T6 |
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| Notes: (1) As an alternative to the above temperature codes, the actual maximum temperature that a device can attain, under normal or overload conditions, may be shown. (2) In North America, if no temperature or temperature code is shown, the maximum external temperature is assumed to be 280°C for Groups A and B, 160°C for Group C and 215°C for Group D. |
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IMPORTANT NOTE
When considering a particular gas, vapour or dust, we must not only consider the Class and Group of the compound, but also the AIT. For example, Ethyl Ether is rated as Class I, Group C, but the AIT is 160°C (320°F), which is lower than the Ruffneck™ FX5 Explosion-Proof Electric Air Unit Heater's T3B rating. Another example would see Hydrogen's AIT at 550°C (1022°F), but it is rated as a Class I, Group B gas. The FX5 is rated for Group C, D, E, F & G only.
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