ATEX Radios in Oil and Gas

In a refinery, a tank farm, a bunkering berth or a gas processing plant, a radio is a potential ignition source carried by hand into an atmosphere that may be flammable. Certification is the answer, and the marking on the case is the whole of the information — provided anyone reads it.

Most compliance failures on real sites are not about buying uncertified equipment. They are about buying the right radio and then getting the assembly wrong.

Classification follows how frequently and for how long an explosive atmosphere is present.

Handsets are certified in practice for Zone 1 and Zone 2, and for Zone 21 and Zone 22 in dust. Zone 0 — the inside of a tank — is not a space people occupy continuously, so a handheld requirement there is rare.

The rule that governs everything: higher category equipment may be used in a lower zone; the reverse is never permitted. Zone 1 equipment works in Zone 2. Zone 2 equipment must not enter Zone 1.

The zone alone is insufficient, because what is in the atmosphere matters as much as how often.

Gas groups, by how easily the substance ignites:

• IIA — propane, petrol and diesel vapours. The least demanding.
• IIB — ethylene, town gas.
• IIC — hydrogen and acetylene. The lowest ignition energies and the hardest to satisfy.

IIC-certified equipment is usable in IIB and IIA. IIA equipment is not usable where hydrogen is present. For dust the equivalents are IIIA (combustible flyings), IIIB (non-conductive dust) and IIIC (conductive dust); a plant with metal dust needs IIIC.

Temperature class caps the maximum surface temperature the equipment may reach, which must stay below the ignition temperature of the substance present:

Higher numbers mean tighter limits and greater protection. T4 is the common class for handsets.

Several protection principles exist; for handhelds the relevant one is intrinsic safety (Ex i). The idea is not to contain a spark but to limit the energy in the circuit so that a spark capable of ignition cannot occur in the first place.

• Ex ia — safe with two independent faults. Zone 0.
• Ex ib — safe with one fault. Zone 1.
• Ex ic — safe in normal operation. Zone 2.

Ex d, flameproof enclosure, works on a different principle: an internal explosion is permitted but prevented from propagating outside. Common on fixed equipment, rare on handsets.

Alongside ATEX there is the North American scheme, UL 913, the US standard for intrinsic safety. Hytera's hazardous-area range includes both ATEX/IECEx and UL913 certified models. In Türkiye the applicable framework is ATEX, with IECEx as the international mutual-recognition scheme; which certificate a site accepts belongs in the specification.

A typical marking looks like this:

`⟨Ex⟩ II 2G Ex ib IIC T4 Gb`

Compare that string against the site's own classification drawing, part by part. If any element is weaker than the area requires, the radio does not belong there — regardless of how it is described in a catalogue.

Certification applies to the assembly, not to the radio body.

A certified handset with a standard battery is not certified. The battery is part of the intrinsic safety design — its energy content, its internal protection, its terminal arrangement are all in the certificate. The same applies to speaker microphones, headsets, antennas and carry cases.

The practical consequences on a site with mixed areas:

• Hazardous-area batteries stocked and stored separately, visually distinguishable from ordinary ones.
• A written rule on which radios cross which boundary, and enforcement at the boundary rather than by good intentions.
• Accessories procured against the certificate, not against the connector.
• Charging outside the classified area, since chargers are almost never certified.

A fleet fails an audit on the battery far more often than on the radio.

In oil, gas and petrochemical facilities: pump and compressor houses, loading gantries, tank farm bunds, separator and process areas, sampling points, jetties and bunkering berths, and drainage systems. Control rooms, administration buildings and workshops are normally unclassified — which is why most sites need a certified subset of the fleet rather than a fully certified fleet.

Dust zones follow the same logic in a different industry: silos, mills, grain handling, flour and sugar processing, wood dust, metal grinding.

Vague ATEX wording produces non-compliant deliveries and is the single most common defect in hazardous-area radio tenders. Instead of "ATEX certified radios", state:

• Zone, gas group and temperature class per area, referencing the site classification drawing.
• The certification scheme accepted — ATEX, IECEx, UL913 — and whether certificates must be supplied.
• Battery and accessory certification stated explicitly, with part numbers.
• Quantities per classified area, so the certified subset is sized correctly.
• Charging arrangements, including where chargers may be located.
• Marking legibility and durability, since an unreadable marking fails an inspection.
• Service arrangements, because repairing a certified device outside an authorised process voids the certification.

The last point deserves emphasis. An ATEX radio repaired by an unauthorised workshop is no longer a certified device, whatever it says on the case. Hazardous-area fleets need a service route that preserves the certificate, and that is a contract term rather than an assumption.