Free engineering calculators and unit convertersceo@instrumentationblog.in
IP, NEMA and Ex Rating Decoder · Free Tool

Ex Equipment Selector: Zone, EPL, Gas Group and T Class

Select the hazardous area zone, the gas or dust group and the ignition temperature. The tool shows the minimum EPL and ATEX category, the T class needed and the protection concepts that fit.

Zone to EPLATEX categoryT classProtection types
°C
Minimum EPLGb (or Ga)
ATEX category2G
Required T classT3 (max surface 200 °C) or higher number
Suitable protection conceptsdb, eb, ib, pxb, pyb, q, ob, mb, plus all Ga types
Group marking neededIIB or higher (IIC covers IIB and IIA; IIIC covers IIIB and IIIA)
Example markingEx db IIB T3 Gb
Advertisement

Selection Rules

Zone 0 → Ga, Zone 1 → Gb, Zone 2 → Gc; Zone 20 → Da, 21 → Db, 22 → Dc
T class: maximum surface temperature must be below the gas autoignition temperature

Higher protection levels may be used in lower risk zones (Ga in Zone 1). Group IIC equipment suits IIB and IIA gases. T classes: T1 450, T2 300, T3 200, T4 135, T5 100, T6 85 °C.

Worked example

Zone 1, IIB gas with autoignition temperature 287 °C: EPL Gb, category 2G, T3 or better (200 °C < 287 °C), for example Ex db IIB T3 Gb.

Key insight: the T class is about the hottest surface, including heat from the process: a transmitter on a 250 °C line can exceed its marked class through conduction.
Advertisement

Frequently Asked Questions

Can Zone 1 equipment be used in Zone 2?

Yes, Gb equipment is suitable for Zone 2.

Is Ex d allowed in Zone 0?

Not on its own; Zone 0 needs Ga equipment such as Ex ia.

How do I find the autoignition temperature?

From IEC 60079-20-1 data or the safety data sheet of the substance.

You May Also Like

Learn more on the blog

Temperature classes in hazardous areas

A practical, field focused guide on instrumentationblog.in that explains the theory behind this tool and how engineers apply it on real plants.

Read Full Article

More IP, NEMA and Ex Rating Decoder

IP Rating Decoder (IEC 60529)IEC 60529, Dust protectionNEMA Enclosure Types and IP EquivalentsNEMA 250, NEMA 4XEx Marking Decoder (ATEX and IECEx)ATEX, IECExHazardous Area Zones, EPL and ATEX CategoriesZone 0, 1, 2, Zone 20, 21, 22IK Impact Rating Decoder (IEC 62262)IK00 to IK10, Impact energy (J)

More Instrumentation Tools

2 toolsInstrument Tag DecoderDecode ISA 5.1 instrument tags and look up every identification letter.6 toolsWire and Cable Color CodesWire colour codes for power, control panels, thermocouples and RTDs by standard.9 toolsPID Tuning ToolsPID tuning calculators, PID form converter and an online PID loop simulator.4 toolsP&ID SymbolsSearchable P&ID symbols for instruments, lines, valves and flow elements.3 toolsPipe and Flange ChartsPipe schedules, ASME B16.5 flange dimensions and pressure ratings.4 toolsThread Size ChartsNPT, BSP and metric thread sizes and a thread identifier for instrument fittings.11 toolsCommunication ProtocolsModbus address, float and CRC tools, RTU timing, RS485 rules and HART commands.17 toolsTroubleshooting GuidesInteractive fault finders for transmitters, flowmeters, valves and loops.18 toolsPractice TestsInstrumentation quizzes with instant scores and explained answers.CalculatorsCalculatorsFree engineering calculators for flow, level, pressure, temperature, valves and more.ConvertersUnit Converters76 converters, 700+ units.