Intrinsically safe two-way radios: what they are and how to choose one

Intrinsic safety (Ex i) is a protection concept defined in IEC 60079-11. It works by limiting the electrical and thermal energy in every circuit of the radio so that any spark or hot surface is too weak to ignite the surrounding explosive atmosphere. Unlike flameproof (Ex d) protection — which contains an explosion inside a heavy enclosure — intrinsic safety prevents ignition from happening in the first place.

For a two-way radio, this means the battery's maximum discharge current, the antenna's radiated power, and the speaker-microphone's electrical connections are all constrained to levels proven safe in testing. A Notified Body (for ATEX) or ExTL (for IECEx) evaluates the complete system — radio body, battery pack, antenna, and all accessories — as a single certified unit. Detailed information on how intrinsic safety compares to other Ex protection methods is available on exknowledge.com.

The practical result is that intrinsically safe two-way radios are lighter and more portable than flameproof alternatives, but have slightly lower transmit power and battery capacity. For handheld use in Zone 1 and Zone 2, intrinsic safety is the dominant and preferred protection concept worldwide.

The certification required depends on where the radio will be used — both geographically and in terms of hazardous area zone classification.

Most manufacturers offer dual ATEX + IECEx certification on a single radio, which covers EU and international markets simultaneously. For sites operating under both IEC and NEC classification systems, radios with triple certification (ATEX + IECEx + UL) are available from Motorola, Kenwood, and Hytera.

Beyond matching the certification to your zone and gas group, several practical factors determine which intrinsically safe two-way radio is right for your operation:

Protocol. DMR (Digital Mobile Radio) is the current industry standard, offering AES-256 encryption, GPS tracking, text messaging, and doubled channel capacity via TDMA. Analogue radios are cheaper but lack encryption and are being phased out by most vendors. NXDN (Kenwood/Icom) and dPMR are niche alternatives with specific vendor ecosystems.

Gas group and temperature class. Most intrinsically safe two-way radios are certified to Ex ib IIC T4 Gb — this covers all gas groups (including hydrogen) and temperature classes down to 135 °C auto-ignition. If your site has only IIA gases (methane, propane), you could use IIA-rated equipment, but IIC radios provide universal coverage with no cost penalty.

Battery life. Intrinsically safe batteries have lower capacity than their standard counterparts because the Ex certification limits maximum energy. Typical runtime is 10–16 hours depending on the transmit-to-listen ratio. For 12-hour shifts, select a radio with at least 14 hours rated battery life to account for GPS and encryption overhead.

Existing infrastructure. If your site already runs a MOTOTRBO repeater network, Motorola radios integrate without additional infrastructure. The same applies to Kenwood NEXEDGE and Hytera DMR systems. Greenfield sites have the freedom to evaluate all vendors — the full multi-vendor comparison table compares all current models side by side.

The table below lists all intrinsically safe two-way radios currently available with ATEX Zone 1 certification. Every model listed carries Ex ib IIC T4 Gb or equivalent.

Battery life based on 5/5/90 duty cycle from manufacturer datasheets. Verify certification on iecex.com.