Reading ATEX markings: “Ex II 3G Ex ic op is IIC T4 Gc” explained character by character

The rating plate of an explosion-protected rugged tablet carries a line such as “Ex II 3G Ex ic op is IIC T4 Gc”. It looks like a code and it is one: every character answers its own question, and together they define the conditions under which the device may be operated in an explosive atmosphere. This article decodes the gas line of the Getac UX10-EX, F110-EX and K120-EX, followed by the dust line. What the zones are and which Ex devices we carry is covered in the article ATEX and explosion protection. How ATEX relates to IECEx and to Class/Division is shown in the article IECEx, ATEX and Class I Division 2. We do not repeat either. We sourced the meaning of the characters from Directive 2014/34/EU, from an information poster of the French institute INERIS (December 2025) and from pages of the testing body NSW TestSafe, all retrieved on 20 October 2026.

The marking at a glance

The manufacturer datasheet of the Getac UX10-EX gives two lines: “Ex II 3G Ex ic op is IIC T4 Gc” for gas and “Ex II 3D Ex ic op is IIIC T130°C Dc” for dust. Both are built the same way. The first part, up to the letter G or D, comes from the EU directive. The second part comes from the IEC 60079 series of standards and describes how the device is built. The table breaks down the gas line.

Group, category and letter: “Ex II 3G”

According to Annex II point 1.0.5 of Directive 2014/34/EU, every device carries the explosion protection mark, followed by the mark for group and category. For group II, the letter G is added for gas, vapour and mist, the letter D for dust, or both. Group I is underground mining with the categories M1 and M2. Group II covers all other areas with the categories 1, 2 and 3.

The category states how much safety the device must provide. According to Annex I, category 1 requires a very high level, even with two independent faults, and is intended for areas where the atmosphere is present continuously, for long periods or frequently. Category 2 requires a high level for areas where it occurs occasionally. Category 3 requires a normal level of safety for areas where an explosive atmosphere is not expected to occur and, if it does, will in all likelihood occur only rarely and for a short time. For gas, Annex II point 2.3.1.1 specifies that for category 3, ignition sources that can occur in normal operation are avoided.

The INERIS poster assigns the categories to the zones of Directive 1999/92/EC: 1G belongs to zone 0, 2G to zone 1, 3G to zone 2, and for dust 1D to zone 20, 2D to zone 21, 3D to zone 22. Our four devices with a complete marking therefore carry category 3 and are rated for zone 2/22. One detail concerns the proof: for category 3, Article 13 of the directive lets the manufacturer rely on internal production control. For categories 1 and 2, the poster adds an EU type examination. If the datasheet also names IECEx, you can look up the certificate in the IECEx online system.

Type of protection: “ic” and “op is”

The type of protection describes the construction method the device uses to avoid becoming an ignition source itself. The small i stands for intrinsic safety under IEC 60079-11. NSW TestSafe names three levels. With ia, the device must not cause ignition in normal operation, even with two countable faults added. With ib, this applies with one countable fault. With ic, it applies to normal operation. According to INERIS, the series ia, ib, ic covers zones 0, 1 and 2. The c therefore sits at the lower end, just as Gc sits at the lower end of the protection levels.

Next comes “op is”. The abbreviation belongs to IEC 60079-28 and, according to NSW TestSafe, means that the emitted visible or infrared radiation does not carry enough energy to ignite the atmosphere. The measured power must not exceed the limit of the standard. Two related abbreviations, “op pr” and “op sh”, confine the radiation in a fibre or another medium, or reduce it to harmless levels through a shut-off. Two types of protection in a row mean that both apply to the device. The datasheet does not say which light sources Getac means. If you want to use a barcode reader or a flash in the Ex area, ask about it for the configuration you choose.

Gas group, temperature class and equipment protection level

IIC and IIIC: how easily the substance ignites

The gas groups differ by their reference gas. According to INERIS, IIA has propane with a maximum experimental safe gap of 0.92 mm and a minimum ignition energy of 0.25 mJ, IIB has ethylene with 0.65 mm and 0.07 mJ, and IIC has hydrogen and acetylene with 0.37 mm and 0.017 mJ. IIC has the smallest values and is therefore the group of the most easily ignitable gases. For dust, INERIS names three groups: IIIA combustible flyings above 500 µm, IIIB non-conductive dust and IIIC conductive dust with a resistivity of up to 1 kΩ·m. NSW TestSafe lists light metal working as a typical location for IIIC, and sugar refineries and grain storage among others for IIIB.

T4 and T130 °C: how hot the housing may get

For gas, a temperature class is given. According to the INERIS poster, the maximum surface temperatures are T1 with 450 °C, T2 with 300 °C, T3 with 200 °C, T4 with 135 °C, T5 with 100 °C and T6 with 85 °C. A T4 device therefore does not get hotter than 135 °C. The poster names diethyl ether with an ignition temperature of 175 °C, which falls into T4, and carbon disulphide with 90 °C, which falls into T6. The device is therefore below the ignition temperature of the ether but above that of the carbon disulphide. This calculation is ours, not the poster’s. A T4 marking is therefore no clearance for every gas of group IIC.

For dust, no class is given, but the temperature itself: “T130°C”. According to the poster, it must be below the ignition temperature of the 5 mm layer minus 75 K and below two thirds of the ignition temperature of the dust cloud. For wheat dust (37 µm), the poster gives 300 °C for the layer and 510 °C for the cloud. That yields limits of 225 °C and 340 °C, and 130 °C is below both. This too is our calculation with the values from the poster.

Gc and Dc: the equipment protection level

The equipment protection level (EPL) comes from IEC 60079-0 and exists as Ga, Gb and Gc for gas, as Da, Db and Dc for dust, and as Ma and Mb for mining. According to NSW TestSafe, Ga is “very high”, Gb is “high” and Gc is “enhanced”, with Da, Db and Dc matching for dust. Dc means no ignition in normal operation. The poster assigns Ga to zone 0, Gb to zone 1, Gc to zone 2, and Da, Db, Dc to zones 20, 21 and 22. Category and protection level therefore say the same thing in two rulebooks: 3G is Gc, 3D is Dc. That is why both appear in the line.

The marking of our six Ex tablets

The table comes from the datasheets on robustbook.bitblade.io. The marking appears there verbatim from the manufacturer datasheet. For the EX80 and the T800 EX ATEX, the documents give only the zone. We therefore decode nothing there and instead transfer the zone following the INERIS poster.

The four fully marked devices carry the same two lines. The marking therefore does not tell them apart. They differ in display (11.6, 12.5, 10.1 and 8 inches) and in operating temperature per datasheet: −21 °C to 60 °C for the F110-EX, −21 °C to 55 °C for the K120-EX, −21 °C to 55 °C for the UX10-EX and −21 °C to 55 °C for the ZX80-EX. According to the article Getac UX10-EX, new generation, the new generation of the UX10-EX keeps the same marking.

For comparison, the Durabook U11I-EX carries “Ex II 3G Ex ic IIC T4 Gc” and “Ex II 3D Ex ic IIIB T135°C Dc” according to its product page. “op is” is absent. For dust it reads IIIB instead of IIIC, and the temperature is 135 °C instead of 130 °C. According to the classification of NSW TestSafe, IIIB covers non-conductive dust, whereas IIIC also covers conductive dust, such as metal dust. If you work in an environment with metal dust, you therefore read the group in the dust line first. The product page gives no reason for the difference.

What the marking does not answer

The marking states the conditions the device has been tested for. Four questions remain with you:

• The operator defines the zone of the site in the explosion protection document. It cannot be read from any device line.
• The marking applies to the device in its certified configuration. Have the configuration you choose, including accessories, confirmed in writing.
• The datasheets do not say for which ambient temperature range T4 and T130 °C apply. Ask the manufacturer before you use the device at the limits.
• The gases and dusts at the site must match the group and the temperature. The explosion protection specialist checks this.

North America uses a different system. The OSHA example in 29 CFR 1910.307 reads “Class I, Zone 0, AEx ia IIC T6”: gas group and temperature class use the same characters, the rest does not. The article on IECEx and Class/Division covers the details. Limits of this article: the standard texts IEC 60079-0, -11 and -28 are paid, and we have not read them. Our statements on them come from the directive, the INERIS poster and NSW TestSafe. The standards govern the binding interpretation. An industry overview of the requirements in industrial settings is on the page Industry.

Frequently asked questions

What does the 3 in “Ex II 3G” mean?

Category 3 under Annex I of Directive 2014/34/EU: devices for areas where an explosive atmosphere is not expected to occur and, if it does, only rarely and for a short time. It corresponds to zone 2 for gas and zone 22 for dust.

May a device with Gc also be used in zone 1?

No. Gc is the lowest of the three gas levels and belongs to zone 2 according to the INERIS poster. Zone 1 requires Gb, zone 0 requires Ga.

Why does “Ex” appear twice in the line?

The first is the explosion protection mark of the directive, followed by group and category. The second opens the normative marking under IEC 60079 with type of protection, group, temperature and protection level.

Is a T4 device approved for every gas of group IIC?

No. IIC describes the ignition energy, T4 the surface temperature. A gas with an ignition temperature below 135 °C, such as carbon disulphide with 90 °C, needs a higher class according to the calculation above. The explosion protection specialist checks the gas list at the site.

Conclusion: which device, which line

If you have to cover zone 2/22 with gases up to group IIC and dusts up to IIIC, you will find the complete marking on the Getac F110-EX, K120-EX, UX10-EX and ZX80-EX. You then choose by display and temperature range, not by the line. For the Getac T800 EX ATEX and the EX80 we cannot decode the marking, because our documents do not state it. The EX80 is the only device with zone 0/20. If you need a character-by-character decoding for it, obtain it from the manufacturer. None of the six devices lists zone 1/21. The RobustBook team is glad to help you match zone, group and temperature to your application.