Explosion protection concepts for energy equipment

Explosion protection in hazardous environments

The UK energy sector is rapidly pivoting to hydrogen to meet 2050 net-zero targets, aiming for 5GW of low-carbon production capacity by 2030. Hydrogen is the cornerstone of decarbonising emission-heavy industries, transport, and heating, while providing flexible, long-term energy storage to balance renewable sources. However, this pivot also narrows the margin for error in hardware design by introducing higher volatility, tighter physical constraints, and, in some cases, closer proximity to human environments. Explosion protection concepts then become less of a theoretical choice or compliance checkbox and more of an engineering constraint that determines material choice, hardware design, form factor, total cost of ownership, and, thus, the commercial viability of the system.

When developing equipment for hazardous areas or ensuring that the transition from isolated industrial zones to decentralised urban energy hubs is safe, the choice of explosion protection concepts determines whether a product is a market-ready solution or a liability requiring potentially costly redesign. What is often underestimated is that this choice doesn’t just affect the enclosure: it has a knock-on effect that trickles down through the entire system architecture, from PCB design and thermal management to installation, inspection, and long-term maintenance.

The basic sequence of explosion protection: Zone differentiation, protection level and technical measures:

Fundamentally, for an explosion to take place, flammable or explosive gases, vapours, mists or dusts will be present. Therefore, before a single piece of hardware is specified, the site or application is categorised into Zones based on the frequency and duration of explosive atmospheres (Ex zones). These zones provide the basis for which protective measures are to be taken and the level of risk that’s present: 

Once the zone is identified, the next question is: what protective measures (e.g., artificial ventilation, oxygen removal, or substitution of flammable substances) can be taken to avoid it? This is referred to as Primary Explosion Protection, and it’s the top priority in safety hierarchies, as it aims to prevent explosions before they occur. When possible, primary explosion protection can result in downgrading the potential risk from Zone 1 to Zone 2, which is generally more cost-effective and avoids over-engineering hardware.

Only after all the possibilities of primary explosion protection have been exhausted can teams move on to determining whether they will need secondary or tertiary explosion protection and select the appropriate explosion protection concept accordingly:

• Secondary explosion protection: Prevents ignition sources such as sparks, hot surfaces, or static electricity from triggering an explosion. Relevant protection concepts include Ex i (Intrinsic), Ex p (Purge) and Ex e (Increased Safety)
• Tertiary explosion protection: Minimises the effects of an explosion if it occurs, such as venting or suppression systems. Relevant protection concepts include Ex d (Flameproof) and explosion relief.

Evaluating key Explosion Protection Concepts

IoT energy devices and equipment requiring secondary or tertiary explosion protection can only be deployed once the conformity certification requirements, such as ATEX and IECEx, have been met. These requirements generally assign the level of protection needed into three categories: containing the explosion, limiting the energy, or isolating the source. In practice, most deployable systems are hybrids and combine multiple concepts across subsystems to balance performance, cost, and certifiability.

Flameproof Enclosures (Ex d)

The Ex d approach assumes an internal explosion will happen. The enclosure is designed to withstand internal pressure without deforming, while the flame paths (precisely engineered gaps at joints and bolts) cool the escaping gases so they cannot ignite the external atmosphere.

• Real-World Application: Large-scale motor starters and switchgear in offshore wind substations.
• The Critical Trade-off: While extremely reliable, Ex d enclosures are heavy and expensive. For a product developer, this translates into higher shipping costs, stricter mounting requirements, and reduced flexibility in modular system design.
• System-Level Implication: Choosing Ex d at the component level often forces the entire system toward mechanical robustness rather than agility, affecting enclosure stacking, cable routing, and even the feasibility of field retrofitting or upgrading.

Intrinsic Safety (Ex i)

Intrinsic safety is the most elegant solution for electronics. Instead of containing an explosion, Ex i limits electrical and thermal energy to levels below those required to ignite a specific hazardous mixture.

• Real-World Application: Handheld diagnostic tools or wireless sensor nodes used in hydrogen refuelling stations.
• The Critical Trade-off: You are limited by power. You cannot run a high-torque motor via Ex i. It forces developers to optimise for ultra-low power consumption, which can constrain processing capability, communication range, and feature sets.
• System-Level Implication: Ex i shifts complexity upstream into circuit design, component selection, and barriers. It also introduces device-level dependencies, meaning certification is often required at the system level, not just per device, particularly in networked or IoT-enabled deployments.

Pressurisation and Purging (Ex p)

Ex p maintains a constant positive pressure of clean air or inert gas inside the equipment housing, ensuring that flammable gases simply cannot enter.

• Real-World Application: Large analyser sheds or control panels in ammonia production plants.
• The Critical Trade-off: The system is only as safe as its gas supply. If the pressure drops, the system must shut down, resulting in costly downtime in a continuous process.
• System-Level Implication: Ex p introduces operational dependencies (e.g., valves, sensors, purge cycles) which extend beyond the product into plant infrastructure. This creates additional failure modes that must be accounted for in both design validation and functional safety strategies.

Additional protection concepts to consider

While the three concept-approaches outlined above cover most strategic decisions, two additional concepts frequently emerge in modern energy systems, particularly as electrification and power density increase.

Increased Safety (Ex e)

Ex e focuses on eliminating ignition risks under normal operating conditions through enhanced insulation, ingress protection, and thermal control.

• Where it fits: Auxiliary systems, terminals, and certain motor applications where arcing components can be designed out.
• The Trade-off: It is less tolerant of degradation over time, so long-term reliability depends heavily on manufacturing quality and environmental sealing.
• System-Level Implication: Ex e is often combined with Ex d or Ex i within a single system, but this introduces interface challenges, particularly around cable entries, connectors, and maintaining protection integrity across boundaries.

Encapsulation (Ex m)

Encapsulation isolates ignition-prone components by embedding them in resin, preventing any interaction with the external atmosphere.

• Where it fits: Battery systems, power electronics, and compact high-density assemblies.
• The Trade-off: Thermal management and repairability. Once encapsulated, components are effectively non-serviceable.
• Real-World Application: Sandvik’s battery-electric mining equipment uses encapsulated subsystems to safely operate in methane-rich underground environments.
• System-Level Implication: Ex m pushes risk containment into materials engineering, but shifts lifecycle considerations—failures become replacement events rather than maintenance tasks, impacting total cost of ownership.

The explosion risk of hydrogen systems

In hazardous environments, gas groups are classified based on their flammable characteristics:

• Group IIA: Low risk, as higher ignition energy is required and the severity of explosion is lower, and includes gases such as propane and methane. Electronic devices designed for these environments have less stringent conformity requirements and are easier and cheaper to certify.
• Group IIB: Medium risk with a faster flame propagation and lower ignition energy than IIA, and includes gases such as ethylene. Devices and equipment deployed in these environments require tighter tolerances, more restrictive component selection, and increased testing requirements.
• Group IIC: Highest risk for extremely fast flame propagation with very low ignition energy, and includes gases such as hydrogen and acetylene. Design implications include tighter mechanical tolerances (e.g., flame paths in Ex d), extremely strict limits on electrical energy (Ex i), and demanding certification testing.

Hydrogen systems carry significant explosion risks due to hydrogen’s unique properties: it’s the smallest, lightest, and most reactive of all gases, allowing it to leak through microscopic cracks, threaded joints, and seals. In addition, hydrogen fires are nearly invisible and therefore hard to detect or locate visually, have a wide flammability range and a low ignition energy, making any leak potentially explosive. This explains why stricter design tolerances and more rigorous testing protocols are required.

From a design perspective, over-engineering for Group IIC when it’s not needed can price your product out of the market. Conversely, underestimating the gas group can lead to catastrophic failure. A balanced approach requires a deep dive into the specific zone classification, gas group, and actual operating conditions of the end-use environment, rather than relying solely on nominal design assumptions.

Design constraints caused by certification friction

One of the least visible but most impactful constraints on explosion-protected products is certification friction.

• System vs Component Certification: A certified component does not guarantee a certifiable system. Integration choices (cabling, interfaces, thermal interactions) often trigger re-evaluation.
• Testing Iterations: Flame paths, temperature rise, and fault conditions frequently require multiple test cycles, each adding time and cost.
• Standards Interpretation: Even within frameworks such as ATEX and IECEx, interpretation can vary among notified bodies, creating uncertainty late in development.

Treating certification as a downstream activity is one of the most common causes of delay. The most efficient teams design for certifiability from the outset and align engineering decisions with testing requirements before prototypes are locked.

Final thoughts on balancing device safety with energy sector innovation

Explosion protection is a multidisciplinary safety strategy that includes engineering solutions, zoning, regulatory compliance, employee training, and routine monitoring. Choosing the right protection concept is a pivot point in the product development lifecycle. If you select Ex d for a product that could have been designed as Ex i, you’ve added unnecessary weight, cost, and maintenance hurdles for your end-user. Equally, selecting Ex i or Ex e without fully understanding system interactions can create hidden constraints that only surface during certification or deployment.

At Ignitec, we don’t just look at the standards; we look at the application. We help developers navigate these trade-offs to create equipment that is not only safe but also commercially viable and operationally efficient.

Are you developing hardware for the hydrogen economy or next-gen energy storage? Let’s discuss how to integrate these explosion protection concepts into your design without compromising on performance.