Temperature Classes

The ignition temperature of a flammable gas/liquid is the lowest temperature of a hot surface at which ignition of the gas/air or vapour/air mixture takes place. The maximum surface temperature of the equipment must therefore be lower than the ignition temperature of the ambient atmosphere.

Temperature classes T1 to T6 have been introduced for electrical equipment within a Group II hazardous area.


 Hazards which will not ignite at temperature below:













The equipment is assigned to a temperature class (shown in the table above) according to its maximum surface temperature. Equipment corresponding to a higher temperature class can also be used for applications requiring a lower temperature class.

For example, a T6 certification for euipment which has a maximum permissible surface temperature of 85°C can be used in T5, T4, T3, T2 and T1 environments.

Similarly, a T4 certification for equipment which has a maximum oermissible surface temperature of 135°C can NOT be used in a T5 or T6 environment, but can be used in T3, T2 and T1 environments.

A T6 Certified product is a good choice as it can be used in all other T classes.


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