Which One Has the Higher Explosion-Proof Level, BT4 or CT4

The explosion-proof classification of CT4 equipment surpasses that of BT4 equipment.

Class And Level	Ignition Temperature And Group
-	T1	T2	T3	T4	T5	T6
-	T＞450	450≥T＞300	300≥T＞200	200≥T＞135	135≥T＞100	100≥T＞85
I	Methane
IIA	Ethane, Propane, Acetone, Phenethyl, Ene, Aminobenzene, Toluene, Benzene, Ammonia, Carbon Monoxide, Ethyl Acetate, Acetic Acid	Butane, Ethanol, Propylene, Butanol, Acetic Acid, Butyl Ester, Amyl Acetate Acetic Anhydride	Pentane, Hexane, Heptane, Decane, Octane, Gasoline, Hydrogen Sulfide, Cyclohexane, Gasoline, Kerosene, Diesel, Petroleum	Ether, Acetaldehyde, Trimethylamine		Ethyl Nitrite
IIB	Propylene, Acetylene, Cyclopropane, Coke Oven Gas	Epoxy Z-Alkane, Epoxy Propane, Butadiene, Ethylene	Dimethyl Ether, Isoprene, Hydrogen Sulfide	Diethylether, Dibutyl Ether
IIC	Water Gas, Hydrogen	Acetylene			Carbon Disulfide	Ethyl Nitrate

BT4 is classified as a Class B temperature group, where the maximum surface temperature of T4-rated devices does not exceed 135°C. CT4 holds a Class C explosion-proof rating, comparable to BT4, and is suitable for environments with hazardous gases such as hydrogen and acetylene, maintaining a maximum surface temperature of 135°C.

Scope of Use

BT4 is suitable for common gases including methane, ethane, petroleum, and hydrogen sulfide.

CT4 encompasses a broader range of less common explosive gases, such as hydrogen and water gas at the CT1 level, acetylene at the CT2 level, and carbon disulfide at the CT4 level.