Which Level of Explosion-Proof Is Higher, CT4 or CT3

Operating d II CT4 devices ensures a lower maximum operating temperature, which increases safety. The term “d” denotes flameproof equipment. The explosion-proof rating for CT4 is superior.

Temperature group of electrical equipment	Maximum allowable surface temperature of electrical equipment (℃)	Gas/vapor ignition temperature (℃)	Applicable device temperature levels
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

T4-rated explosion-proof equipment holds a higher standard and can substitute for BT4-rated devices; thus, using CT4 instead of BT4 ensures compliance and enhanced safety.