25 Year Industrial Explosion-Proof Manufacturer
Technical Article
Technical Comparisons

Which Level of Explosion-Proof Is Higher, CT1 or CT4

The CT4 explosion-proof classification is considered high.

Gas ClassificationTemperature Group
-T1T2T3T4T5T6
-T>450450≥T>300300≥T>200200≥T>135135≥T>100100≥T>85
IMethane
IIAEthane, Propane, Acetone, Phenethyl, Ene, Aminobenzene, Toluene, Benzene, Ammonia, Carbon Monoxide, Ethyl Acetate, Acetic AcidButane, Ethanol, Propylene, Butanol, Acetic Acid, Butyl Ester, Amyl Acetate Acetic AnhydridePentane, Hexane, Heptane, Decane, Octane, Gasoline, Hydrogen Sulfide, Cyclohexane, Gasoline, Kerosene, Diesel, PetroleumEther, Acetaldehyde, TrimethylamineEthyl Nitrite
IIBPropylene, Acetylene, Cyclopropane, Coke Oven GasEpoxy Z-Alkane, Epoxy Propane, Butadiene, EthyleneDimethyl Ether, Isoprene, Hydrogen SulfideDiethylether, Dibutyl Ether
IICWater Gas, HydrogenAcetyleneCarbon DisulfideEthyl Nitrate

All considered, each device holds an IIC rating, indicating uniformity across this metric; however, distinctions are found within their temperature classifications: T6 devices have a maximum surface temperature of 85°C, T4 devices peak at 135°C, and T1 devices can reach up to 450°C.

T4-rated explosion-proof equipment is highly esteemed and can fully substitute for T1-rated devices. In essence, replacing CT1 equipment with CT4 in any application ensures safety.

Dana Lin
Dana Lin Senior Compliance & Safety Engineer

Specializes in global explosion-proof standards (ATEX/IECEx) and rigorous technical compliance, providing the foundational engineering data for industrial safety.

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