Which Explosion-Proof Level Is Higher, CT4 or CT5

Exd IIC T4 and Exd IIC T5 share similar explosion-proof ratings, with the sole distinction being the maximum temperature each can reach during operation.

Temperature Classification for Electrical Equipment	Maximum Permissible Surface Temperature of Electrical Equipment (°C)	Gas/Vapor Ignition Temperature (°C)	Applicable Equipment Temperature Class
T1	450	＞450	T1~T6
T2	300	＞300	T2~T6
T3	200	＞200	T3~T6
T4	135	＞135	T4~T6
T5	100	＞100	T5~T6
T6	85	＞85	T6

The maximum permissible surface temperatures differ: for Exd IIC T4, it is 135 degrees Celsius, whereas for Exd IIC T5, it is capped at 100 degrees Celsius.

Given that lower operating temperatures enhance safety, the explosion-proof classification CT5 is considered superior to CT4.