ATEX zones explained: choosing the right communication equipment

Look beyond the ATEX zone number

Equipment Category 1 is generally associated with Zones 0 and 20, Category 2 with Zones 1 and 21, and Category 3 with Zones 2 and 22. However, experienced ATEX professionals know that the complete equipment marking provides far more useful information than the category number alone.

For example, the Motorola Solutions MOTOTRBO R7Ex IIC models carry the gas marking II 2G Ex ib IIC T4 Gb and the dust marking II 2D Ex ib IIIC T130°C Db. These markings identify the equipment group, protection method, gas or dust group, surface temperature and Equipment Protection Level.

Each element should correspond with the site’s hazardous-area documentation. This applies to radios, sensors and cameras. A general claim that a device is “ATEX-certified” does not confirm that it is suitable for every classified area.

Consider how gas-group certification affects coverage

IIC certification covers gases with lower ignition energies than Groups IIA and IIB. It may therefore seem sensible to standardise the radio fleet around IIC devices. However, the intrinsic-safety measures needed for IIC certification can restrict radio-frequency output.

The Entel DTEx ATEX radio, for example, is available in IIA and IIC versions. The IIA model operates at up to four watts, while the IIC version operates at one watt.

The MOTOTRBO R7Ex full-keypad model is also available as a four-watt IIA device, while its IIC variants operate at up to two watts.

That difference can affect coverage around steel structures, processing units, terminals and large outdoor estates. Selecting the broadest gas-group certification without accounting for reduced transmit power may result in dead spots or additional repeater costs.

Where the site only requires IIA equipment, an IIA radio may provide stronger coverage. Where workers regularly move between differently classified areas, IIC standardisation may still make sense, but it should be supported by a detailed coverage survey.

Check temperature markings carefully

Temperature class is sometimes treated as a secondary entry on the certificate, but it can determine whether equipment is suitable for a particular substance.

Gas equipment normally carries a T-class, while dust equipment is marked with a maximum surface temperature in degrees Celsius. These values must be compared with the ignition characteristics of the gases, vapours or dusts present.

Ambient temperature also matters. A radio may operate electronically in very hot or cold conditions without being certified for hazardous-area use at those temperatures. The R7Ex, for example, is listed with an ambient operating range of -30°C to +60°C.

This should be checked in exposed terminals, cold areas, process heat zones and vehicles where radios may be left between shifts. The product certificate and any specific conditions of use should always take priority over the broader temperature range shown in a sales data sheet.

Treat accessories as part of the certified radio

An ATEX radio should be assessed together with its battery, antenna, remote speaker microphone, headset and breathing-apparatus connection.

A physically compatible accessory is not automatically approved for the same ATEX zone or protection level. Even a battery or antenna supplied by the same manufacturer may invalidate the certified configuration if it is not listed for that model.

The Entel DTEx range, for example, supports selected certified accessories from Dräger, Savox and MSA. Similarly, Motorola ATEX radios are designed to work with approved accessories, including selected remote speaker microphones, batteries and compatible communication headsets. This can be useful for teams working with breathing apparatus, but the complete combination of radio, accessory and PPE should be checked.

Where hearing protection is required, certified communication headsets such as Peltor headsets should also be selected to ensure compatibility with the radio and the hazardous-area certification requirements.

Sites should also set clear procedures for charging, changing batteries and connecting accessories. These tasks may need to take place outside the hazardous area, depending on the device certificate and manufacturer’s instructions.

Match the radio interface to the role

A full keypad and display are useful for some users, but they are not necessary for every worker.

The MOTOTRBO R7Ex full-keypad model may suit supervisors, permit coordinators and maintenance teams managing several talk groups.

The R7Ex non-keypad model’s simpler interface may be easier for operators who use a small number of channels while wearing gloves.

Other options available through Radiocoms include:

• The Hytera HP79X Ex, an IIC-certified DMR radio with clear audio and modern controls.
• The Hytera PD795Ex, which may suit sites with an established Hytera DMR network.
• The MOTOTRBO DP4401Ex, offering a simpler interface and integrated GPS.*
• The MOTOTRBO DP4801Ex, which adds a keypad, display and messaging.*
• The Motorola Solutions MTP8500Ex, developed for organisations using TETRA infrastructure.

*Subject to availability 

The existing radio network should narrow the shortlist before individual handset features are compared.

Assess gas and dust areas separately

Dust certification should not be treated as an extension of the gas assessment. An IP68 enclosure may resist dust and water, but an IP rating does not replace ATEX dust certification.

The marking should identify the relevant dust group, such as IIIA for combustible flyings, IIIB for non-conductive dust or IIIC for conductive dust. The permitted surface temperature should also account for the dust’s ignition temperature and any deposits that may build up on the radio.

Inspection and cleaning procedures are equally relevant. Dust deposits can reduce heat dissipation, cover certification labels and conceal cracks or other damage.

Test emergency functions from end to end

Emergency buttons, man-down alerts, lone-worker functions and location tracking should be tested across the complete communication path.

The test should confirm who receives an alert, what information appears, whether the emergency call can interrupt normal traffic and what happens when the user is indoors or near the edge of radio coverage.

The Honeywell and Motorola Connected Safety system can link portable Honeywell gas detectors with compatible MOTOTRBO radios. Gas alarms, worker status and location data can then pass through the radio system to the control room.

Commissioning should cover detector pairing, failed-connection warnings, alarm priorities, radio coverage and control-room response procedures. An alert reaching the software is useful, but staff must also know what it means and how to respond.

Maintain control of the radio fleet

ATEX compliance continues throughout the radio’s working life. Cracked housings, damaged seals, unofficial batteries, contaminated connectors or unapproved repairs may affect the original certification.

Fleet records should cover each radio, its approved accessories, inspection status, repair history and software configuration. Damage that appears cosmetic may still affect protection, particularly around the battery latch, casing or accessory connector.

Choosing an ATEX communications provider

The more difficult parts of radio selection are rarely shown in a basic comparison table. They concern coverage, transmit power, PPE compatibility, emergency workflows and long-term maintenance.

Radiocoms works across DMR, MOTOTRBO and TETRA systems and can assess ATEX zones alongside user roles, site coverage, connected gas detection and existing infrastructure.

Visit the Radiocoms Oil and Gas industry page for more information, or contact us to discuss communication systems for refineries, terminals, processing plants, pipelines and other hazardous working environments.