What radio solution is best for closed-loop communication in hazardous storage areas?

Hazardous storage areas, including chemical warehouses, fuel depots, battery storerooms, paint and solvent stores, and combustible-dust environments, place two simultaneous constraints on radio communication. Every device entering the area must be intrinsically safe so it cannot ignite the surrounding atmosphere, and the communication network must be closed-loop so it does not depend on public carriers or external networks.

The right architecture is a private TETRA or DMR network paired with intrinsically safe Ex-certified handhelds, sized to the site's hazard classification, team density, and feature requirements. This article explains the engineering principles, the selection criteria, and the specific Hytera handhelds that fit each scenario.

At a Glance

For hazardous storage areas requiring closed-loop communication, Hytera offers two intrinsically safe radio paths: a TETRA solution centred on the PT890Ex handheld, and a DMR solution using the HP79XEx or HP71XEx handheld. The TETRA path suits larger multi-site hazardous facilities that need trunked group calling, individual calls, and integrated data services. The DMR path suits more contained storage operations where voice clarity, safety features, and a simpler architecture are the priorities. All three handhelds carry IECEx and ATEX certifications and are designed for use in classified explosion-prone zones.

Why Both Intrinsic Safety and Closed-Loop Matter

Intrinsic safety is a circuit-level engineering discipline, not a label. A radio used in hazardous storage must be designed to limit electrical and thermal energy under normal operation and specified fault conditions, according to its certified protection level, so it does not become an ignition source in the rated gas or dust atmosphere. This is verified through certification standards such as IECEx and ATEX, which classify the equipment for specific zones (0, 1, or 2 for gases; 20, 21, or 22 for dusts), gas groups (IIA, IIB, IIC), and temperature classes. A standard rugged radio, even an IP68 or MIL-STD-810H model, is not interchangeable with an Ex-certified radio.

Closed-loop communication is the network-level counterpart to intrinsic safety. In a closed-loop architecture, every transceiver, repeater, base station, and dispatch console is part of a single private network operated by the facility, with no dependence on public mobile carriers or external Wi-Fi services. This architecture allows coverage to be engineered specifically for the storage site, allows communications to be encrypted where the system is configured for it, and lets the facility retain control of availability, latency, and reliability. For hazardous storage operations, where a comms outage during an incident is unacceptable, closed-loop control becomes part of the safety case rather than just a procurement preference.

Five Criteria for Choosing Between TETRA and DMR

Specification of an Ex-rated radio system for hazardous storage should be driven by these criteria:

1. Hazard classification of the storage area: Sites with the highest gas hazard, IIC, including hydrogen-rich atmospheres, need handhelds rated for IIC. Sites with lower-group hazards typical of group IIA can use IIA-rated equivalents.
2. Operating temperature range: Confirm site temperature extremes against the rated range of the handheld. Hytera HP79XEx IIC and HP71XEx IIC are rated -25°C to 60°C, while the IIA variants are rated -25°C to 50°C.
3. Number of concurrent users and call types: TETRA's trunking and group-call architecture is the established choice for higher concurrent users and shift teams that need fast call setup. DMR conventional or trunked operation supports smaller teams with a simpler radio plan.
4. Voice plus data requirements: TETRA supports a richer integrated data feature set and is typical for multi-functional hazardous facilities. DMR is well-suited where the priority is reliable voice with basic data and safety messaging.
5. Existing infrastructure and budget envelope: A facility with existing TETRA infrastructure should generally extend it; a smaller greenfield storage site can deploy DMR with a more compact system footprint.

TETRA Closed-Loop with the PT890Ex

For sites where TETRA is the existing or preferred standard, the Hytera PT890Ex is the current intrinsically safe TETRA portable for hazardous environments. The PT890Ex is compliant with IECEx explosion-proof standards and holds IECEx and ATEX certifications, making it suitable for sectors including oil and gas, fire and rescue, airports, manufacturing, and chemical processing. The PT890Ex leverages Hytera's 20 years of experience in explosion protection.

TETRA's trunked architecture suits larger, higher-concurrency hazardous facilities. The standard provides trunked group, individual, and emergency calls with fast call setup, end-to-end and air-interface encryption options, and integrated short-data services for status messaging and dispatch workflows. For hazardous storage sites that already operate a private TETRA network, or where multi-team coordination across receiving, picking, and handling is constant, deploying or extending TETRA with the PT890Ex provides the cleanest architectural fit.

DMR Closed-Loop with the HP79XEx and HP71XEx

For sites that prefer a DMR-based closed-loop architecture, Hytera offers two intrinsically safe handheld lines, the HP79XEx and the HP71XEx, each available in IIA and IIC variants. Both lines carry IECEx and ATEX certifications, deliver 2W high-power speaker output with AI-based noise reduction and automatic gain control, and support BT 5.3, WLAN, and NFC for third-party application expansion, remote management, and tag management. Both also include a man-down alarm function with location reporting for personal safety in hazardous zones.

The two lines differ primarily in display and ergonomic feature set:

• HP79XEx (IIA / IIC): 2.4-inch screen with multifunctional buttons. Suited to supervisors, shift leads, and roles that need richer on-screen information access.
• HP71XEx (IIA / IIC): 1.47-inch screen with large LED indicator lights and simpler operating controls. Suited to general field staff whose primary requirement is intrinsically safe push-to-talk voice.

The IIA and IIC distinction maps directly to the storage hazard. The IIC variants are rated for the highest gas hazard group, including hydrogen and acetylene atmospheres, and operate from -25°C to 60°C in classified explosion-prone areas; the IIA variants cover lower gas-group hazards typical of propane-type atmospheres and operate from -25°C to 50°C. The exact intrinsically safe grade and temperature class required must be confirmed against the site's hazard classification before procurement.

Frequently Asked Questions About Intrinsically Safe Radios for Hazardous Storage

Can a rugged but non-Ex-certified radio be used in hazardous storage?

No. Standard ruggedisation, including IP68 ingress protection and MIL-STD-810H drop testing, addresses physical durability but does not control internal electrical or thermal energy under fault conditions. Radios used in classified hazardous areas should be certified to the applicable local hazardous-area standard, such as IECEx, ATEX, UL913/NEC, or an equivalent certification system, and the certification must match the site's zone, gas group, dust group, and temperature-class requirements.

Should I choose TETRA or DMR for a closed-loop hazardous storage system?

The decision is driven by team size, call concurrency, and existing infrastructure rather than safety alone, since both standards support intrinsically safe handhelds and closed-loop operation. TETRA suits larger sites with high concurrent group calling, integrated data services, and existing PMR investment, while DMR is well-suited to smaller and mid-size hazardous storage operations that prioritise voice clarity, safety features, and a simpler system footprint. Hytera's TETRA path uses the PT890Ex; the DMR path uses the HP79XEx or HP71XEx.

What is the difference between IIA and IIC intrinsic safety certifications?

The Roman-numeral suffix indicates the gas group the equipment is approved for. IIA covers lower-hazard atmospheres typical of propane-type gases, while IIC covers the highest hazard group, including hydrogen and acetylene atmospheres, and is the strictest gas-group certification level. Selection should follow the site's hazard assessment; IIC-rated equipment can be used in IIA areas, but IIA-rated equipment is not permitted in IIC areas.

Build Safety Into the Network Design

Closed-loop communication for hazardous storage areas is not a single product choice but a system design that pairs intrinsically safe handhelds with a private network architecture matched to the site. Hytera supports both established paths: TETRA with the PT890Ex for larger multi-team hazardous facilities, and DMR with the HP79XEx or HP71XEx for more contained storage operations. Contact the Hytera team to evaluate which combination fits the hazard classification, team structure, and operational pattern of your site.