How to identify the model number of an explosion-proof distribution box

The model number of an explosion-proof distribution box encodes its protection type, applicable hazardous zones, gas or dust group, temperature class, and equipment protection level.Key Components of the Model NumberEquipment GroupI: For mining environments (methane gas)II: For other explosive atmospheres outside mines, such as industrial gas or dust areas Category / Zone1 / Zone 0: Very high risk, continuous or long-term explosive atmosphere2 / Zone 1: High risk, occasional explosive atmosphere3 / Zone 2: Normal risk, rare or brief exposure Atmosphere TypeG: Gas, vapor, or mistD: Combustible dustSome devices may have dual markings like G/D for mixed hazards Protection MethodEx d: Flameproof enclosure, containing internal explosionsEx e: Increased safety, preventing sparks or overheatingEx i: Intrinsically safe, limiting energy to prevent ignitionEx t: Dust protection, preventing ignition of combustible dust Gas/Dust GroupIIA, IIB, IIC: Specifies the type of gas the box can safely handle, with IIC being suitable for the most volatile gases like hydrogen Temperature ClassT1–T6: Maximum surface temperature of the enclosure; lower numbers indicate higher allowable temperatures before ignition risk Equipment Protection Level (EPL)Gb / Gc: Gas protection levelsDb / Dc: Dust protection levelsIndicates the degree of protection and suitability for specific zones ExampleA model number like II 2G Ex db IIB T4 Gb can be interpreted as:II: Industrial explosive atmosphere2G: Category 2, suitable for Zone 1 gas areasEx db: Flameproof enclosureIIB: Gas group, suitable for ethylene and similar gasesT4: Maximum surface temperature 135°CGb: Equipment protection level for gas, suitable for Zone 1 Additional NotesSome manufacturers, like HRMD92 series, include extra identifiers for enclosure material (stainless steel, aluminum), hinge type, and optional features like meters, breakers, or PLCs .Customization may be reflected in the model number or suffixes, indicating special configurations or additional safety features.Always cross-reference the model number with the certification label to ensure compliance with ATEX, IECEx, or local standards . By understanding each segment of the model number, you can determine the suitability of the distribution box for specific hazardous environments, its protection method, and operational limits.