Which Level of Explosion-Proof Is Higher, CT2 or CT4

It is evident that CT4 holds a higher explosion-proof rating. Notably, explosion-proof motors feature the IICT4 designation but lack the IICT2 marking.

Temperature Class IEC/EN/GB 3836	Maximum Surface Temperature of Equipment T [°C]	Ignition Temperature of Combustible Substances [°C]
T1	450	T＞450
T2	300	450≥T＞300
T3	200	300≥T＞200
T4	135	200≥T＞135
T5	100	135≥T＞100
T6	85	100≥T＞8

This distinction stems from the temperature classifications of explosion-proof electrical devices: T4 devices are designed to maintain a maximum surface temperature below 135°C, whereas T2 devices allow a maximum surface temperature up to 300°C, deemed excessively risky.

Consequently, CT4 is the preferred choice; CT2 is generally avoided.