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Hazardous Area Code Translator

Decode a North American NEC Class/Division marking, an IEC/IECEx Ex string, or an ATEX marking, and translate between the two systems. It surfaces the parts most cross-reference charts bury: the gas-group lettering runs in opposite order (NEC Group A is IEC IIC), NEC Group A and B both collapse to IIC, and a Division is not a single Zone.

A marking translator for hazardous (classified) locations. Type a North American NEC marking ("Class I Div 1 Group D T3"), an IEC/IECEx Ex string ("Ex db IIB T4 Gb"), or an ATEX marking ("II 2 G Ex d IIC T4 Gb"), and the translator decodes it position by position and converts it to the other system. It identifies the marking scheme, the hazard (gas, dust, or fibres), the area grade (Division or Zone), the gas or dust group, the equipment protection level (EPL) and ATEX category, the type of protection (flameproof d, intrinsic safety i, increased safety e, pressurization p, encapsulation m, type n, dust protection t), and the temperature class. The translation carries a directionality and a lossy or ambiguous flag on every hop, because the two systems are not a clean one-to-one map: the gas-group lettering is reversed (NEC Group A, acetylene, is the worst gas, and so is IEC IIC), NEC Group A and B both map to IIC so the distinction is lost going one way and ambiguous coming back, and NEC Division 1 spans both Zone 0 and Zone 1. This is a reference decode for understanding equipment markings, not a tool for re-classifying a hazardous area, which is an engineering exercise under the governing code.

Pro Tip: The trap that catches people is the reversed gas-group lettering. In the NEC system, Group A is acetylene, the most easily ignited gas, and the letters get less severe down to Group D (propane). In the IEC system it is the opposite: IIA is the least severe (propane) and IIC is the most severe (hydrogen and acetylene). So NEC Group D maps to IEC IIA, and NEC Group A maps to IEC IIC. Worse, NEC Group A (acetylene) and Group B (hydrogen) both collapse into the single IEC group IIC, so a US nameplate that says "Groups A, B, C, D" becomes "IIC" in IEC terms and loses the A-versus-B detail. Going the other way, an IEC IIC device is ambiguous in NEC terms: it could be Group A or Group B, and you have to know whether the application is acetylene or hydrogen to pick. The translator flags every one of these hops instead of hiding them, which is the difference between understanding a marking and guessing at it.

Read the Hazardous Area Code Guide for the full Class/Division versus Zone reference, the gas-group reversal table, and how to read an Ex string position by position

Hazardous Area Code Guide →

Decode a NEMA enclosure Type, including the hazloc Types 7 and 9 that carry a Class and Division

NEMA Enclosure Rating Decoder →

Decode a motor nameplate; explosion-proof motors carry the hazloc marking alongside the electrical data

Motor Nameplate Decoder →

Decode an IP rating, the ingress-protection code that sits next to the Ex marking on an IEC nameplate

IP Rating Decoder (IEC 60529) →

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Hazardous Area Code Translator
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How It Works

  1. Type the marking

    Enter a NEC marking ("Class I Div 1 Group D T3"), an IEC/IECEx Ex string ("Ex db IIB T4 Gb"), an ATEX marking ("II 2 G Ex d IIC T4 Gb"), or a dust marking ("Ex tb IIIC T80C Db"). The translator is tolerant of spelling: it accepts Roman or Arabic class and division numbers, lowercase or uppercase, and partial markings (a bare "IIC", "T4", or "Group D").

  2. Read which system it is

    The detected banner names the marking scheme (NEC Class/Division, IEC/IECEx Ex, ATEX, or partial) and the hazard kind (gas, dust, or fibres). The prefix tells you the scheme: Ex is IECEx, AEx is the US zone system under NEC Article 505, and EEx is the legacy CENELEC marking.

  3. Walk the position-by-position decode

    Every token in the marking gets its own row with the raw code, a label, and a plain-English meaning: the class or equipment group, the division or zone, the gas or dust group with its example substance, the protection type and what zones it covers, the EPL, and the temperature class with its maximum surface temperature.

  4. Read the translation

    The translation card shows the equivalent marking in the other system, prominently. If the translation loses information (NEC Group A and B both map to IIC) it is flagged "Lossy". If the reverse direction is ambiguous (IEC IIC could be NEC Group A or B) it is flagged "Ambiguous on the way back". Each lossy or ambiguous hop is explained in a note so you know exactly where the imprecision is.

  5. Check the temperature class

    The temperature class (T1 through T6, with the NEC subdivisions T2A through T3C) is the maximum surface temperature the equipment can reach, and it is identical in both systems. It must stay below the autoignition temperature of the specific gas or dust present. On a dust marking the surface temperature is often written directly (T80C means 80 degrees C) instead of a T-class, and the translator carries it across.

  6. Export the decode

    PDF export produces a branded report with the position-by-position decode table, the translated marking, the lossy and ambiguous flags, the translation notes, the standing field notes, and the source citation. CSV export packages the same fields. The share button puts the exact marking in a coworker browser without retyping.

Built For

  • A reliability engineer holding an imported instrument marked "Ex db IIB T4 Gb" and needing the NEC equivalent ("Class I Division 1 Group C T4") before installing it in a US plant
  • A maintenance planner reading a US nameplate "Class I Div 1 Groups A B C D T6" and confirming it covers everything an IEC IIC T6 device would
  • A buyer comparing a European explosion-proof motor (II 2 G Ex d IIC T4 Gb) against a US Class I Division 1 spec and catching that IIC means Group A or B
  • An instrument tech decoding "Ex ia IIC T4 Ga" and confirming the intrinsic-safety protection is rated for Zone 0, the most severe gas area
  • A plant operator reading a dust marking "Ex tb IIIC T80C Db" and translating it to Class II Division 1 Group E or F with the 80 degrees C surface limit intact
  • A specifier confirming that an ATEX category 2 device is approved for Zone 1, not Zone 2, because the category number is one higher than the zone number
  • A panel builder checking that a temperature class T3 (200 degrees C) on a marking is hot enough below the autoignition point of the gas in the area
  • A trainer using the reversed gas-group table to explain why NEC Group A and IEC IIA are opposite ends of the severity scale

Features & Capabilities

Three-System Decode In One Tool

The translator reads all three marking schemes: the North American NEC Class/Division system (NEC Article 500), the IEC/IECEx Zone system, and the European ATEX marking. It detects the scheme from the tokens, decodes each position, and translates to the other system. The prefix (Ex, AEx, EEx) is decoded so you know whether a US marking is using the Division system or the parallel Zone system under Article 505.

The Reversed Gas Group, Surfaced

The single most error-prone part of any hazloc cross-reference is the gas-group lettering, which runs in opposite order between the two systems. The translator encodes the reversal explicitly (NEC A and B both map to IEC IIC, C to IIB, D to IIA) and flags the loss going one way and the ambiguity coming back, with the example gas named (acetylene, hydrogen, ethylene, propane) so the severity is obvious.

Lossy And Ambiguous Flags On Every Hop

The translation is never presented as a clean equivalence when it is not one. A Division-to-Zone hop is flagged lossy because Division 1 spans both Zone 0 and Zone 1. A IIC-to-NEC hop is flagged ambiguous because it could be Group A or B. Each flag carries a note explaining exactly where the imprecision is, so you translate with your eyes open.

Full Protection-Type And EPL Decode

The translator decodes the type of protection (flameproof d, increased safety e, intrinsic safety i with its ia/ib/ic sub-levels, pressurization p, encapsulation m, oil immersion o, powder filling q, type n, and dust protection t) with the principle behind each and the zones it covers. It decodes the Equipment Protection Level (Ga through Dc) and ties it to the zone, the ATEX category, and the NEC division.

Temperature Class And Dust Surface Temp

The temperature class (T1 through T6 with the NEC subdivisions) is decoded into its maximum surface temperature, identical across both systems. Dust markings that state the surface temperature directly (T80C) are recognised and carried into the translation, because the surface limit must stay below the dust ignition temperature.

Reference Decode, Not An Authority

The tool is framed throughout as a reference decode for understanding equipment markings, not a tool for re-classifying a hazardous area or selecting equipment, which are engineering decisions under the governing code (NEC, IEC 60079-14, or the ATEX directive). The NEC Division and the IEC Zone systems are parallel legal systems in the US and may not be mixed within one installation.

PDF And CSV Export

PDF export uses the shared ToolGrit programmatic generator: the position-by-position decode as a table, the translated marking with its lossy and ambiguous flags, the translation notes, the standing field notes, and the source citation, with a branded header and the standard disclaimer footer. CSV export packages the same fields for records or a procurement file.

Light And Dark Mode, WCAG AA

Standard ToolGrit light and dark theme with WCAG AA contrast on the lossy and ambiguous badges, verified readable in both themes. The detected banner uses an aria-live region so screen readers announce the decode when the marking changes. The mobile layout at 375 px keeps the decode list readable without horizontal scrolling.

Comparison

NEC (Class / Division) IEC / IECEx (Zone) Gas example Direction note
Class I (gas) Group II equipment - Class I = gas; IEC Group II = surface gas. Same numeral, opposite meaning vs NEC Class II.
Division 1 Zone 0 and Zone 1 - Lossy: Division 1 spans two zones (EPL Ga and Gb).
Division 2 Zone 2 - Division 2 corresponds to Zone 2 (EPL Gc).
Group A IIC acetylene A and B both map to IIC; A/B detail is lost.
Group B IIC hydrogen IIC back to NEC is ambiguous (A or B).
Group C IIB ethylene Unambiguous both ways.
Group D IIA propane, methane Unambiguous both ways. Note the reversal: NEC D is the mildest, IEC IIA is the mildest.
Class II Group E IIIC metal dust Conductive dust. IIIC back to NEC is ambiguous (E or F).
Class II Group F IIIC coal, carbon Carbonaceous dust is conductive in IEC terms, so F also maps to IIIC.
Class II Group G IIIB grain, flour, wood Non-conductive dust.
T-code (T1 to T6) T-code (T1 to T6) - Identical in both systems. Max surface temp; must stay below autoignition.

References

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Frequently Asked Questions

They are two systems that grew up independently. In the NEC, Group A is acetylene (the most easily ignited gas) and the severity drops to Group D (propane). In the IEC, the order is reversed: IIA is the least severe (propane) and IIC is the most severe (hydrogen and acetylene). So NEC Group D maps to IEC IIA, and NEC Group A maps to IEC IIC. The translator handles the reversal for you and names the example gas so the severity is clear.
Because the IEC combines acetylene and hydrogen into the single most-severe group IIC, while the NEC keeps them separate as Group A (acetylene) and Group B (hydrogen). Going from NEC to IEC, A and B both collapse to IIC and the detail is lost. Coming back from IEC to NEC, IIC is ambiguous: it could be A or B, and you have to know whether the application involves acetylene or hydrogen to pick. The translator flags this as ambiguous and explains it.
No. The NEC Division system has two area grades (Division 1 and Division 2); the IEC Zone system has three (Zone 0, Zone 1, Zone 2 for gas). Division 1 spans both Zone 0 and Zone 1, and Division 2 corresponds to Zone 2. So a Division-to-Zone translation is approximate: a Division 1 device is typically suitable for Zone 1 (EPL Gb), and Zone 0 needs the higher EPL Ga. The translator flags the Division-to-Zone hop as lossy.
They sound similar and mean opposite things. NEC "Class II" is a combustible-dust area. IEC "Group II" (equipment group II) is surface industry for gas, as opposed to Group I, which is mining. Same Roman numeral, opposite meaning. This is a common source of confusion, which is why the translator reads the whole marking rather than any single token.
The temperature class is the maximum surface temperature the equipment is allowed to reach, and it is identical in NEC and IEC. T1 is 450 degrees C, T2 is 300, T3 is 200, T4 is 135, T5 is 100, and T6 is 85. The lower the number, the hotter the surface allowed, but the class must always sit below the autoignition temperature of the gas or dust present. The NEC adds finer subdivisions (T2A through T3C) that the IEC does not use.
It is the ATEX equipment block. "II" is the equipment group (II is surface industry, I is mining). "2" is the equipment category, which maps to the zone the device is approved for, with an off-by-one: category 1 is for Zone 0, category 2 for Zone 1, category 3 for Zone 2. "G" is the atmosphere (G for gas, D for dust). So "II 2 G" is surface-industry gas equipment approved for Zone 1. The off-by-one (category equals zone plus one) is a common trap, so the translator states it explicitly.
No. This is a reference decode for understanding what an equipment marking means and what it is rated for. Classifying a hazardous area, and selecting and installing equipment, are engineering exercises under the governing code (NEC Articles 500-506, IEC 60079-14, or the ATEX directive). The NEC Division system and the IEC Zone system are parallel legal systems in the US that may not be mixed within a single installation. Use the translation to understand imported equipment, then have a qualified engineer confirm the area classification and the installation.

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