A comprehensive review of risks and mitigation strategies for safe hydrogen infrastructure deployment

As hydrogen gains momentum as a clean and versatile energy carrier for decarbonizing hard-to-abate sectors, ensuring the safety of hydrogen infrastructure becomes critical for its widespread adoption. This review draws on peer-reviewed literature, industrial reports, and international standards for hydrogen technologies. It systematically examines safety risks across the hydrogen value chain, from production to end-of-life and assesses the effectiveness of existing mitigation strategies as well as identifying key research gaps. Common risks such as hydrogen leaks, over-pressurization, and material degradation are present at nearly every stage. Less frequent but potentially severe hazards include the risk of ice formation or equipment damage from cryogenic hydrogen leaks, and toxic exposures from chemical carriers like ammonia or hydrides used for hydrogen storage and transport. The mitigation technologies evaluated include leak detection systems, quick-release valves, emergency ventilation, and both material-based and physical barrier systems. While these safety solutions provide considerable protective potential, their long-term effectiveness depends on real-time responsiveness, and regulatory enforcement. The review also highlights critical gaps in predictive modeling, material durability under extreme conditions exacerbated by climate change, and human error analysis. Emerging technologies, such as AI-enabled safety systems and digital twins, remain underexplored, and current hydrogen safety frameworks have a limited understanding of hydrogen combustion behavior and effective fire suppression strategies. To support the safe and scalable deployment of hydrogen infrastructure, the study calls for targeted research, stakeholder education, and harmonized safety standards. This review provides a timely synthesis of risks and controls to guide future development, policy, and innovation in hydrogen safety. This review will support industry stakeholders, and researchers in developing safer, more reliable, and standardized hydrogen infrastructure.

1 Introduction

In recent years, there has been a surge in research on energy carriers driven by the global push for cleaner, more sustainable energy solutions to address climate change and reduce dependence on fossil fuels (Zhang L. et al., 2024). With the growing energy demand, there is a need for more efficient, environmentally friendly ways to store, distribute, and convert energy. Among the various energy carriers, hydrogen is gaining attention due to its versatility, high energy content per unit of mass (120 MJ/kg), and potential to serve as a zero-emission energy carrier when produced from renewable resources (Staffell et al., 2019; Abohamzeh et al., 2021; Autrey and Chen, 2023). Unlike fossil fuel-based carriers, hydrogen produces only water when used in fuel cells, making it a cleaner alternative for power generation, transportation, and industrial processes (Brandon and Kurban, 2017; Hassan et al., 2024; Zhang L. et al., 2024). Additionally, hydrogen can be stored for long periods and distributed over long distances, which makes it suitable for balancing intermittent renewable energy sources like solar and wind (Ishaq et al., 2022).

Hydrogen is also being integrated into industrial processes and emerging decarbonization initiatives. For instance, fossil-free steel production, exemplified by the HYBRIT project, demonstrates hydrogen’s potential to significantly reduce carbon emissions (HYBRIT, 2024). The HYBRIT (Hydrogen Breakthrough Ironmaking Technology) initiative, developed by SSAB, LKAB, and Vattenfall in Sweden, aims to replace coal-based blast furnaces with hydrogen-based direct reduction to produce steel with water as the only by-product. Beyond energy storage and heavy industry, hydrogen’s flexibility in being used as both an energy carrier and a process chemical broadens its application across multiple sectors. However, realizing hydrogen’s potential at scale requires an equally robust infrastructure, spanning production, storage, distribution, and utilization. Each phase introduces safety challenges, and as hydrogen infrastructure expands, so does the complexity and severity of associated risks.

While hydrogen’s benefits as a clean energy carrier are compelling, its unique physical and chemical properties present considerable safety concerns. Hydrogen is a highly flammable gas with a wide flammability range of 4%–75% in air and 4%–95% in pure oxygen (Hu et al., 2020). The lower flammability limit (LFL) of 4% is not exceptional compared to other fuels (see Table 1), but the extremely high upper limit makes hydrogen prone to ignition across a broader concentration range than most other gases. Furthermore, hydrogen burns with an almost invisible flame, making fire detection difficult during leak events (Schefer et al., 2009). In addition, its ignition energy is exceptionally low, about 0.02 millijoules (mJ), compared to 0.29 mJ for gasoline vapor, meaning that even minor sparks or static electricity can ignite hydrogen-air mixtures (Ehsan Hosseini and Abdul Wahid, 2016; Faye et al., 2022).

Table 1

Table 1. Properties of hydrogen gas compared to other fuels measured at standard temperature and pressure (STP).

Hydrogen’s small molecular size and high diffusivity contribute to its rapid dispersion in the atmosphere. It has a gas dispersion rate of approximately 0.61 cm²/s, which is significantly faster than that of gasoline vapor or methane. Although this property allows for faster dilution in open environments, it also increases the likelihood of leaks from micro-cracks, faulty seals, and porous materials. Combined with its low density of 0.0899 kg/m³ at standard conditions, hydrogen tends to rise and accumulate near ceilings or under roofs, posing a significant risk in enclosed or semi-confined areas (Raj et al., 2024). Moreover, hydrogen flames propagate at high speeds. Its laminar flame speed in air can exceed 3 m/s, making it the fastest among common fuels, and difficult to suppress once ignition occurs (Dong et al., 2010). These distinctive safety properties are summarized in Table 1, which compares hydrogen with other common fuels such as gasoline and methane. This makes hydrogen stand out across multiple parameters for its high-risk potential, despite providing clear environmental advantages when safely managed.

Beyond its combustion behavior, hydrogen presents significant challenges in material compatibility. A well-documented phenomenon, hydrogen embrittlement, occurs when hydrogen atoms infiltrate metal structures, causing a loss of ductility and leading to brittle fractures (Meda et al., 2023). This degradation process affects high-strength steels, nickel-based alloys, titanium, and even some polymers. In polymers, hydrogen exposure can lead to cracking, swelling, or permeability changes, especially in materials like polyethylene and certain elastomers used in sealing applications. As a result, pipelines, storage tanks, valves, and fittings may suffer structural failure if not specifically designed or coated to withstand long-term hydrogen exposure (Laadel et al., 2022; Li Q. et al., 2024).

The scale of hydrogen infrastructure further amplifies these risks (Agyekum et al., 2022). In large-scale production facilities, whether based on electrolysis, steam methane reforming (SMR), or biomass gasification, the volume of hydrogen handled increases the probability and consequence of leaks, over-pressurization, and system failure. As production scales, storage systems must also accommodate higher capacities. This elevates the risks associated with high-pressure vessels, cryogenic liquefaction, and the use of chemical carriers. These conditions introduce challenges such as increased boil-off losses, greater explosion potential, and more complex safety requirements for containment and venting. Moreover, the co-location of multiple storage units within large hydrogen hubs increases the risk of cascading failures in the event of an incident. Distribution systems, especially pipelines and high-pressure transport, become more vulnerable at scale to embrittlement, pressure surges, and ignition sources due to extended networks and diverse operating environments. Finally, utilization in fuel cells, industrial burners, and refueling stations presents operational risks such as gas mixing failures, electrical shocks, and fire hazards in confined spaces, all of which are magnified when scaled across large facilities.

As hydrogen transitions from a niche fuel to a fundamental component of global decarbonization strategies, safety must be treated as a system-wide priority, not an afterthought. While isolated incidents may stem from localized technical faults, most hydrogen-related accidents emerge from cascading failures, such as embrittlement leading to leaks, which accumulate and ignite due to improper ventilation or faulty detection. Despite the growing interest in hydrogen technologies, there remains a critical gap in understanding and managing safety risks holistically across the entire hydrogen value chain. Managing these interdependencies requires a lifecycle approach that addresses risks holistically, across production, storage, distribution, and end-use phases.

There is currently no integrated framework that systematically identifies, evaluates, and mitigates safety risks throughout the hydrogen lifecycle, including end-of-life. This review therefore addresses three core objectives. First, it identifies and categorizes the critical safety risks across the hydrogen value chain, highlighting both common and less visible hazards. Second, it evaluates the effectiveness of current mitigation strategies, including leak detection systems, automatic shutoff valves, ventilation solutions, and barrier technologies. Third, it identifies key research and technological gaps that must be bridged to ensure the long-term safety and public acceptance of hydrogen infrastructure. This review serves as a one-stop-document that synthesizes available knowledge and identifies critical gaps to support the safe, scalable, and responsible deployment of hydrogen technologies globally.

2 Risk analysis across the hydrogen lifecycle

2.1 Hydrogen lifecycle

The hydrogen value chain comprises a series of interdependent stages: production, storage, distribution, utilization, and end-of-life processing. Hydrogen can be produced from various primary sources, including water, biomass, natural gas, coal, and other renewable and non-renewable raw materials. Traditional methods of hydrogen production include SMR, which extracts hydrogen from natural gas. Other methods involve coal and biomass gasification, which produces hydrogen from heating coal and biomass at high temperatures (Minutillo et al., 2018). These methods are energy-intensive and release significant amounts of carbon dioxide (CO₂) and other greenhouse gases. As a result, they are unsustainable due to their reliance on fossil fuels and their contribution to climate change. While these processes are currently the most cost-effective, they negate the environmental benefits of using hydrogen as a clean energy carrier. Hence, water electrolysis has gained attention as a more sustainable method of hydrogen production. Electrolysis involves splitting water (H₂O) into hydrogen and oxygen using electricity, which, when produced by renewable energy sources like wind or solar, produces zero emissions (Calabrese et al., 2024).

Once produced, hydrogen is typically stored in several forms. It can be compressed as a gas at pressures of 300–1,000 bar and ambient temperatures, liquefied at −253 °C under low pressure, or absorbed into solids such as metal hydrides. Other storage methods include cryo-compressed hydrogen, which combines high pressure with low temperature, and liquid organic hydrogen carriers (LOHCs), which chemically bind hydrogen for safer distribution and release. Each storage method presents unique challenges in terms of safety, energy efficiency, and infrastructure, particularly when scaling up for industrial or widespread energy applications. The choice of storage depends on the specific use case and requires careful consideration of the risks and benefits of each method (Zhang J. et al., 2024).

Distribution of hydrogen is done via cylinders, specialized trucks, pipelines, or ships, depending on the scale and distance of distribution. Pipelines are often used for local or regional distribution, however, their installation can be costly. They also require significant safety measures due to the small molecular size of hydrogen and embrittlement, which makes it prone to leakage (Li J. et al., 2024). For long-distance distribution, hydrogen is typically liquefied or stored in high-pressure containers and moved using trucks or ships. Each distribution method introduces challenges related to infrastructure and safety, particularly in minimizing risks like leaks, explosions, and energy losses during transit.

After distribution, hydrogen is utilized across multiple sectors, such as power generation, transportation, and various industrial processes. Finally, a critical yet often overlooked step in the hydrogen value chain is the circular use of materials and equipment at end-of-life. This includes the recycling and recovery of components from electrolyzers, fuel cells, tanks, and pipelines, many of which contain valuable rare materials such as platinum, nickel, and advanced composites. Figure 1 shows the various sectors in the hydrogen chain and some of the methods applied in each stage.

Figure 1

Figure 1. The hydrogen value chain and associated lifecycle stages, including production, storage, distribution, utilization, and end-of-life processing.

2.2 Hydrogen production risks

A primary concern of hydrogen production is the risk of hydrogen leaks. Hydrogen leaks, however, are rarely isolated. They are often the result of more fundamental failures. One major contributor is over-pressurization, especially in storage and distribution systems, where hydrogen is handled at pressures reaching up to 1,000 bar. Another foundational cause of leaks is material degradation, which includes the specific phenomenon of hydrogen embrittlement. Material degradation is particularly severe in storage tanks and distribution pipelines that are exposed to hydrogen over extended periods, often under high pressure and fluctuating temperatures. Hydrogen embrittlement is best understood not as a separate risk, but as a subset of the broader issue of material degradation, which also includes corrosion, fatigue, and thermal cycling, all of which compromise the structural integrity of hydrogen infrastructure.

Therefore, in a broad sense, the risks associated with hydrogen infrastructure form a cascading chain: for instance, over-pressurization and material degradation cause leaks; leaks lead to accumulation; and accumulation, when combined with ignition sources, results in fire or explosion, see Figure 2. This interdependence makes hydrogen safety a system-wide concern that requires proactive mitigation strategies across all phases of the value chain.

Figure 2

Figure 2. Risk pathways in hydrogen systems.

These findings emphasize that while individual technical failures may appear minor, their interactions can be dangerous. This reinforces the need for robust system designs, hydrogen-compatible materials, real-time monitoring, and integrated safety protocols to prevent cascading failures throughout the hydrogen lifecycle.

Several accidents have occurred in hydrogen production sites in recent years. For instance, in 2019, an explosion occurred at a hydrogen production pilot plant in Gangneung, South Korea, which utilized alkaline water electrolysis. The incident was attributed to a combination of oxygen spillover and human error. Investigations revealed that leaked hydrogen was ignited by static electricity, likely due to inadequate earthing (grounding) connections. The resulting explosion caused two fatalities and six injuries (Bohacikova and Ruiz Pérez, 2025). In 2001, a fire and explosion at a hydrogen production plant occurred due to the spontaneous ignition of a hydrogen-oxygen mixture in high-pressure feed lines. The initial explosion caused welds and joints in the storage banks to fail, releasing large quantities of hydrogen and leading to a secondary explosion (Wen et al., 2022). Similarly, an operator at Laporte Industries in the UK died from burns when a membrane rupture caused a hydrogen leak into an oxygen separator, igniting the mixture (Calabrese et al., 2024).

According to Calabrese et al. (2024), hydrogen production through SMR and electrolysis presents distinct safety challenges. SMR involves handling large quantities of hydrogen at high temperatures and pressures, creating risks of accidental hydrogen releases that can form flammable atmospheres. In contrast, electrolysis presents risks related to high electrical currents, which may cause electric shocks, short circuits, or fires. Chemical exposure is another concern in electrolysis, as electrolytes such as potassium hydroxide or sulfuric acid can pose health risks, including skin and eye irritation, respiratory issues from inhaling fumes, and chemical burns upon contact (Portarapillo et al., 2020; Muscetta et al., 2022). Coal and biomass gasification also present significant safety and environmental risks during hydrogen production. In coal gasification, high temperatures and pressures create the potential for equipment failures, gas leaks, and toxic emissions, particularly carbon monoxide and sulfur compounds, which pose health hazards and environmental concerns (Škvareková et al., 2019). The handling of ash and slag also increases the risk of operational hazards (Hosseini and Gupta, 2015). In biomass gasification, gas leaks and fires can occur due to incomplete combustion or improper sealing. Additionally, chemical exposure to tars, particulates, and volatile organic compounds can lead to health risks and operational inefficiencies (Mishra et al., 2015). Table 2 outlines the key risks associated with hydrogen production processes. Each risk is paired with its underlying causes and potential consequences.

Table 2

Table 2. Key risks in hydrogen production and their consequences.

2.3 Hydrogen storage risks

As shown in Figure 1, hydrogen is stored in various ways: as compressed gas in underground caverns, cylinders, or pressure vessels; as cryogenic liquid in cryogenic tanks; as cryo-compressed hydrogen combining high pressure and moderate to high temperature; or through chemical and liquid organic hydrogen carriers (LOHC) (Gas, 2024). Moradi and Groth (2019) categorized hydrogen storage into two main groups: physical-based and material-based storage. Physical-based storage involves storing hydrogen as either compressed gas, cryogenic liquid, or in a cryo-compressed state, with each method presenting different challenges related to pressure, temperature, and energy efficiency. Material-based storage, on the other hand, relies on chemical or physical sorption, using materials like metal hydrides or porous structures (e.g., metal-organic frameworks, MOFs) to absorb and release hydrogen. These storage methods face technical challenges that need further development.

Compressed hydrogen, stored at extremely high pressures, presents a significant risk of leaks and tank ruptures. The high pressure increases the interaction of hydrogen with materials, leading to hydrogen embrittlement, which weakens storage containers over time. This increases frequency of leaks (Okonkwo et al., 2023). In the event of over-pressurization or structural failure, hydrogen can be rapidly released, leading to potential jet fires, explosions, and property damage upon ignition. Cryogenic hydrogen storage, where hydrogen is stored at extremely low temperatures (−253 °C), introduces additional challenges. At these low temperatures, materials become brittle, increasing the risk of leaks and structural failure. Furthermore, direct contact with liquid hydrogen (LH₂) can cause severe cryogenic burns, as it rapidly freezes the skin and other tissues. Additionally, the rapid expansion of hydrogen gas upon warming can lead to blow-outs, posing significant risks during storage and transfer operations. Another concern is the potential for air to liquefy upon contact with extremely cold surfaces, leading to the accumulation of liquid oxygen. This can create highly reactive mixtures, increasing the risk of combustion or explosion. The formation of ice or solid air can obstruct valves and piping systems, compromising the integrity and functionality of storage units (Verfondern et al., 2021). Also, failures in insulation or temperature control can cause rapid evaporation (boil-off), leading to over-pressurization and potential safety hazards (Moradi and Groth, 2019).

For cryo-compressed hydrogen storage, which combines pressure, typically ranging from 250 to 700 bar, and low temperatures, between −253 °C and −193 °C, the risks of both high pressure and cryogenic conditions are compounded (Kircher et al., 2011). This method stores hydrogen in a dense state, leveraging the coexistence of liquid and gas phases to maximize storage capacity and reduce boil-off losses, rather than compressing LH₂ directly. It encounters similar challenges with material interactions, such as hydrogen embrittlement and thermal degradation, but also demands more advanced handling to prevent accidents related to high-pressure blowouts and potential fires (Garifullina et al., 2024).

When using LOHCs, safety concerns primarily arise from the properties of the chemicals involved. For instance, formic acid, a common LOHC material, is highly corrosive and can cause severe chemical burns to the skin, eyes, and respiratory tract. Exposure to formic acid at concentrations above its occupational exposure limit (typically 5 ppm over an 8-h workday) can lead to health complications, including metabolic acidosis and systemic toxicity if inhaled or ingested (Dalus et al., 2013). On the other hand, Dibenzyl Toluene (DBT), another frequently used LOHC, poses uncertainties regarding its toxicity. While DBT is generally classified as having low acute toxicity, its long-term health effects remain insufficiently studied (Jeong et al., 2024). Current data on DBT does not clearly define risks such as carcinogenicity or organ toxicity, though concerns exist around potential impacts from prolonged exposure. Although LOHCs enhance hydrogen storage and distribution safety by converting hydrogen into a more stable liquid form, the chemicals involved introduce significant health hazards and operational challenges.

Lastly, chemical hydrogen storage, such as using ammonia or methanol, presents risks. Hydrogen is stored in ammonia through the synthesis of ammonia via, e.g., the Haber-Bosch process, which bonds hydrogen with nitrogen, and in methanol by combining hydrogen with carbon monoxide through the methanol synthesis process. Ammonia is toxic, and brief exposure can cause severe irritation or fatal poisoning, while methanol is also highly toxic and flammable (Ali et al., 2024). The use of ammonia and methanol as hydrogen carriers introduces risks that can exacerbate the dangers during their release, particularly during the storage and discharge phases. Table 3 shows a summary of some of the risks associated with hydrogen storage.

Table 3

Table 3. Risks in hydrogen storage and their consequences.

2.4 Hydrogen distribution risks

The distribution of hydrogen, whether by cylinders, pipeline, road, rail, or ship, requires careful management to mitigate risks such as leaks, fires, explosions, and material degradation (Guy and Julien, 2022). There have been some incidents related to hydrogen distribution. For instance, a hydrogen explosion occurred at the Air Products hydrogen transfill facility in Santa Clara, California, in 2019, where a major hydrogen leak from an open pipe triggered a fire and explosion. Investigations attributed the cause to equipment failure, which led to the uncontrolled release of hydrogen (Melideo et al., 2019). The key risks stem from the high pressures in distributing compressed hydrogen, the cryogenic conditions for LH₂ distribution, and the potential for material degradation (such as hydrogen embrittlement) in the infrastructure over time (Garifullina et al., 2024). In particular, pipelines used for hydrogen distribution can experience corrosion or embrittlement, increasing the likelihood of leaks or ruptures (Zhang et al., 2023). Compressed hydrogen gas is typically distributed at pressures of up to 700 bar, and any failure in the transport containers or pipelines can lead to rapid hydrogen release, which increases the risk of fire or explosion, especially if the hydrogen accumulates in enclosed spaces (Kleszcz and Assadi, 2023). Additionally, improper handling of cryogenic hydrogen and vibrations during distribution can result in boil-off or venting issues, where the warming of LH₂ leads to increased pressure and, if improperly managed, can cause tank ruptures or accidents (Matveev and Leachman, 2023). Furthermore, hydrogen’s small molecular size allows it to diffuse through many materials, making the integrity of storage and distribution containers a critical concern. Material fatigue, particularly through hydrogen embrittlement in pipelines and tank materials, can lead to catastrophic failures. Distribution incidents can lead to severe environmental impacts if hydrogen leaks occur, as well as significant hazards for personnel involved in distribution operations. Lastly, co-locating hydrogen pipelines with power transmission lines introduces additional distribution risks due to potential electrical interference, alternating current corrosion, and increased susceptibility to leaks (Hugestam et al., 2024). When pipelines are positioned near high-voltage lines, there is an elevated risk of material degradation, which could lead to hydrogen leaks or even pipeline ruptures. This is a significant problem given the high availability of ignition sources at power lines and substations. Table 4 outlines the major risks associated with hydrogen distribution, their underlying causes, and potential consequences.

Table 4

Table 4. Hydrogen distribution risks and their consequences.

2.5 Hydrogen utilization risks

The utilization of hydrogen, whether in fuel cells, industrial processes, etc., presents safety risks. These risks stem from the flammability of hydrogen, the high pressures involved in its use, and its interaction with materials and electrical systems (Sinay et al., 2019). The key risks include fire and explosion hazards, especially in confined spaces, as well as risks associated with the use of fuel cells and hydrogen combustion processes. Fuel cells rely on the precise separation of hydrogen and oxygen to prevent explosive mixtures. However, faulty membranes and electrical malfunctions can result in hydrogen leaks, increasing the risk of fire and explosion hazards. The high electrical currents in fuel cells also introduce risks of electric shock or short circuits (Bultel et al., 2007). In confined spaces, hydrogen leaks can displace oxygen, creating an asphyxiation risk.

Similarly, hydrogen is often used under high pressure in industrial processes and refueling stations. Failures in pressure regulators, relief valves, or containment systems can result in over-pressurization, causing ruptures and gas releases that lead to explosions or fires. Several real-world incidents have demonstrated the risks associated with high-pressure hydrogen storage and refueling operations. For example, in June 2024, a newly opened hydrogen refueling station in Gersthofen, Germany, operating at pressures between 350 and 700 bar, experienced an explosion shortly after opening (Leigh Collins, 2024). Although no injuries were reported, the incident highlighted the risks associated with high-pressure hydrogen storage and refueling operations. Similarly, in June 2019, an explosion occurred at a hydrogen fueling station near Oslo, Norway, due to a hydrogen gas leak from a tank with an incorrectly mounted plug in a high-pressure storage unit. The explosion injured three people when a pressure wave triggered airbags in their cars nearby (Reuters, 2021). These incidents highlight the need for rigorous safety protocols, regular inspections, and advanced leak detection technologies to mitigate the risks associated with high-pressure hydrogen systems.

Hydrogen combustion in industrial processes carries the risk of incomplete combustion or the formation of explosive hydrogen-oxygen mixtures. Material degradation due to hydrogen embrittlement is also a significant concern, as prolonged exposure to hydrogen weakens metals, increasing the likelihood of equipment failure (Calabrese et al., 2024). Hydrogen’s flammability makes static discharge or sparks from electrical systems or friction a potential ignition source (Hydrogen Safety Panel, 2020). When used as a process chemical in processes like combustion, hydrogen can produce harmful by-products such as nitrogen oxides, especially when burned in air at high temperatures leading to environmental pollution and health risks (Sigal and Nizhnik, 2020). Table 5 highlights the key risks in hydrogen utilization, and the causes and consequences of such risks.

Table 5

Table 5. Hydrogen utilization risks and their consequences.

2.6 Hydrogen infrastructure end-of-life risks

The end-of-life (EoL) phase of hydrogen infrastructure, often underemphasized in lifecycle assessments, presents distinct and growing safety challenges as hydrogen systems scale. This phase involves the decommissioning, dismantling, repurposing, and disposal of hydrogen-related components such as storage tanks, pipelines, electrolyzers, compressors, fuel cells, and chemical carriers (Invernizzi et al., 2020). Improper management at this stage can lead to environmental contamination, fire and explosion hazards, and human health risks.

A major safety concern is the presence of residual hydrogen in tanks, pipelines, and storage vessels, which can remain even after systems are decommissioned. Without proper purging and inerting, these residues may form flammable or explosive atmospheres, especially during cutting, welding, or crushing operations (European Industrial Gases Association EIGA, 2024). EoL processing of material-based storage systems, such as metal hydrides, chemical hydrides, and liquid organic hydrogen carriers (LOHCs), introduces additional hazards. These systems often contain reactive or toxic substances like ammonia, methanol, formic acid, or dibenzyl toluene (DBT) (Markiewicz et al., 2015). Inadequate neutralization or containment of these chemicals during decommissioning may result in toxic exposures, fires, or environmental contamination. The disposal of hydride materials without passivation may also trigger thermal runaway or hydrogen release, especially when exposed to moisture or air (Chen et al., 2017). One of the ongoing challenges in the hydrogen sector is the limited availability of comprehensive, standardized guidelines for the recycling and end-of-life (EoL) handling of components such as fuel cells and storage tanks across jurisdictions. Standards like SS-ISO 22450:2023 provide requirements for sharing information related to the recycling of rare earth elements, however, they do not address other critical materials found in hydrogen technologies, such as platinum-group metals, nickel alloys, or carbon composites (Swedish Standard Institute, 2023a). As a result, these valuable materials may not be efficiently recovered, leading to both economic loss and environmental risk. Informal recycling practices, particularly in regions with limited regulatory guidelines, heighten the risk of chemical exposure and unregulated emissions.

Finally, improper repurposing of used hydrogen equipment, such as reusing tanks or pipelines without structural testing, can result in catastrophic failure if embrittled or degraded components are unknowingly put back into service. Inadequate traceability systems and the absence of EoL certification protocols for hydrogen infrastructure exacerbate this risk (Ustolin et al., 2020). While end-of-life management is often underrepresented in hydrogen safety literature, several international standards and guidelines have begun to incorporate decommissioning protocols and EoL considerations for hydrogen systems. The SS-ISO 19880-1:2022 standard, which outlines general requirements for hydrogen refueling stations, includes provisions for system decommissioning, purging, and leak prevention during shutdown and disassembly (Swedish Standards Institute, 2023b). Similarly, ISO/TR 15916:2015, which addresses basic hydrogen safety, emphasizes the importance of safe venting and removal of residual hydrogen from containers and piping systems at the end of service life (SIS - Svenska Institutet för Standarder, 2022). In Europe, the EU Directive 2012/18/EU (Seveso III) requires that operators of facilities handling dangerous substances, including hydrogen, implement full lifecycle safety plans, including decommissioning procedures (European Parliament & Council of the European Union, 2012). However, most of these standards focus on operational safety rather than comprehensive circular economy strategies. There remains a pressing need to expand existing standards or develop new ones that address component recycling, traceability, and material recovery to ensure sustainable and safe hydrogen infrastructure development across its full lifecycle. Table 6 summarizes the key risks associated with the end-of-life phase of hydrogen systems, along with their underlying causes and potential consequences.

Table 6

Table 6. Hydrogen end-of-life risks and their consequences.

2.7 Common and uncommon risks across all stages of the value chain

2.7.1 Common risks

Across the hydrogen value chain, several risks consistently reappear, with hydrogen leaks standing out as the most critical. These leaks are prevalent in every stage and represent the convergence point of multiple upstream failures. Due to hydrogen’s small molecular size and high diffusivity, even microscopic imperfections in equipment can result in significant leakage. These leaks are difficult to detect and, when they occur in confined or poorly ventilated areas such as storage facilities, garages, tunnels, or underground systems, they can lead to dangerous accumulations. In the presence of ignition sources, the consequences may escalate rapidly into fires or explosions. Due to hydrogen’s low ignition energy, even minimal sources, such as static electricity, friction, or electrical equipment, can trigger an explosion. This is particularly relevant during the utilization phase, where hydrogen interacts with high-frequency mechanical systems and electrical components.

2.7.2 Uncommon risks

Uncommon risks in the hydrogen value chain occur less frequently but can have serious safety and health implications. Cryogenic storage systems face the unique hazard of air liquefaction on cold surfaces, leading to the accumulation of liquid oxygen, a highly reactive substance that heightens the risk of combustion. LOHCs like formic acid and dibenzyl toluene introduce chemical hazards. Formic acid is highly corrosive and poses risks such as chemical burns and metabolic acidosis. The long-term toxicity of dibenzyl toluene remains uncertain, raising concerns about carcinogenicity and organ damage. Additionally, hydrogen accumulation in confined or poorly ventilated areas can displace oxygen, creating asphyxiation risks even before reaching flammable concentrations. In SMR or gasification facilities, carbon monoxide (CO) poses an even more serious threat due to its toxicity and undetectable nature, requiring continuous monitoring and ventilation. These risks, though less prominent in public discussions, demand targeted mitigation strategies to ensure safe and sustainable hydrogen deployment.

2.8 Environmental risks in hydrogen infrastructure

Hydrogen gas itself is not a direct greenhouse gas (GHG), thus, it does not absorb infrared radiation like CO₂ or CH₄. However, vented hydrogen can indirectly contribute to climate change. In the atmosphere, H₂ reacts in ways that increase the concentrations of other GHGs. It can extend the lifetime of methane by reacting with tropospheric OH radicals that would otherwise destroy CH₄. This can lead to the formation of ozone in the lower atmosphere. Studies estimate that leaked hydrogen has a global warming effect ∼11 to 12 times that of CO₂ per unit mass over a 100-year timeframe (Alsulaiman, 2024). This is an indirect global warming potential (GWP), reflecting the effect hydrogen has on methane and ozone (hydrogen itself eventually oxidizes to water). Thus, releasing large quantities of H₂ regularly could erode some of the climate benefit of using hydrogen as a clean fuel. It’s worth noting that hydrogen’s indirect GWP is still much lower than that of unburned methane; one analysis found that the climate impact of hydrogen leakage is about one-third that of an equivalent methane leak (Chen et al., 2024). Nonetheless, as the hydrogen economy grows, preventing leaks/vents is seen as important for climate reasons. In summary, occasional small vents/leaks have a negligible climate effect, but frequent or high-volume leakage or venting of H₂ is environmentally undesirable due to these indirect greenhouse effects.

3 Hydrogen risks mitigation

3.1 Hydrogen leak detection

Effective hydrogen leak detection technologies are essential for identifying and responding to leaks promptly, to minimize potential hazards. A variety of sensor technologies have been developed for this purpose, each with its own strengths and limitations. Table 7 presents a summary of the technologies.

Table 7

Table 7. A list of hydrogen detectors, key features, effective ranges, applications, and reliability.

Catalytic bead sensors are commonly used to detect hydrogen within the lower explosive limit (LEL) range. These sensors operate by using two beads, one active and one reference. The active bead is coated with a catalyst that reacts with hydrogen, generating heat that changes its electrical resistance. The reference bead serves as a baseline comparison (Marsh and Cleary, 2009). While these sensors are widely used in industrial settings, they have limitations such as degradation over time in environments with high humidity or contaminants. This necessitates regular calibration or replacement. Furthermore, they tend to consume more power than other sensor types, which can limit their efficiency in energy-sensitive applications (Swager et al., 2024).

Electrochemical sensors provide high precision in detecting hydrogen concentrations, even at parts per million (ppm) levels, making them suitable for sensitive environments (Russ et al., 2024). These sensors rely on electrodes placed in an electrolyte solution. When the hydrogen gas interacts with the working electrode, an electrical signal is generated proportional to the hydrogen concentration. Electrochemical sensors are highly accurate, however, they are susceptible to cross-sensitivity, where the presence of other gases can interfere with the readings. They also have a limited operational lifespan and require periodic maintenance to ensure consistent performance (Austin et al., 2006).

Ultrasonic sensors are effective in detecting hydrogen leaks by identifying the unique acoustic signature produced by escaping gas (Fecarotta and Janowski, 2021). These sensors are particularly useful in noisy industrial environments, where they can detect leaks in the range of 0.1–10 kg/s, depending on the leak size and pressure differential. However, ultrasonic sensors may struggle to detect very small leaks or those occurring at low pressures, as these leaks produce minimal ultrasonic signals (Seo et al., 2021). Environmental conditions, such as high ambient noise levels or temperature fluctuations, can also affect their performance.

Semiconductor sensors are widely used for detecting low concentrations, typically around 0.4% by volume, and are cost-effective for applications such as battery storage systems. These sensors use metal oxide materials that change their electrical resistance when exposed to hydrogen (Phanichphant, 2014). While they are sensitive and affordable, semiconductor sensors are prone to drift over time, requiring regular recalibration. Additionally, their slower response time can delay the detection of critical leaks (Tang et al., 2022).

Thermal conductivity (TC) sensors measure hydrogen concentrations by detecting changes in heat transfer caused by hydrogen’s thermal properties. These sensors are particularly useful in high-concentration applications such as hydrogen storage. Conventional devices, however, are not sensitive enough for trace-level leak detection (<100 ppm), although recent micro-electro-mechanical systems (MEMS) designs are beginning to push TC detection limits down into the low-ppm range (Zhang Y. et al., 2024).

Emerging technologies, such as nanoplasmonic sensors, introduce further advancements in hydrogen detection. These sensors use highly sensitive and selective nanoplasmonic sensing to detect hydrogen even in mixed-gas environments. Their compact design and energy efficiency make them promising for integration into existing systems (Weyrauch et al., 2025). However, as a relatively new technology, nanoplasmonic sensors face challenges in large-scale industrial deployment, including higher initial costs and the need for specialized expertise.

The reliability of these sensors depends on factors such as sensitivity, calibration, and environmental suitability. For instance, accurate detection requires proper calibration to the expected hydrogen concentrations in the application environment. The environmental conditions, such as temperature and humidity, also influence the performance of these systems. While traditional technologies have been proven effective in various industrial applications, emerging technologies hold the potential for greater sensitivity, selectivity, and miniaturization. In addition, the selection of a hydrogen leak detection system is not only influenced by technical performance but also by cost considerations, the area to be monitored, and the number of sensors required. Sensor costs vary significantly depending on the technology; for instance, catalytic bead sensors tend to be more affordable, while emerging technologies like nanoplasmonic sensors are relatively expensive due to their advanced capabilities (Göktürk et al., 2021). The area of detection required for a given project also plays a vital role in determining sensor choice and quantity. For larger industrial facilities or production plants, where widespread coverage is needed, fewer, more robust sensors, such as ultrasonic or thermal conductivity sensors, may be sufficient to cover a larger area (Shu et al., 2016). In contrast, more confined environments such as laboratories, battery storage, or enclosed spaces may require higher-density deployment of electrochemical or semiconductor sensors, as these technologies exhibit higher precision for smaller areas (Al-Okby et al., 2021). Typically, the number of sensors for a project depends on factors such as the facility’s size, anticipated leak rates, and the required detection sensitivity. For example, industrial applications might deploy multiple sensors at key points, such as hydrogen storage tanks, piping systems, or ventilation areas, to ensure full coverage and minimize the risk of undetected leaks (Swager et al., 2024). Conversely, smaller or more localized systems may require fewer sensors, but with careful placement to ensure effective monitoring. Balancing cost with the required level of detection sensitivity and area coverage is essential in planning a hydrogen leak detection system that is both cost-effective and efficient.

In Europe and other regions, hydrogen leak detectors must comply with various regulatory standards and certifications to ensure safety and performance. These regulations include certifications like ATEX (Atmosphères Explosibles) and IECEx, which are mandatory for equipment used in explosive atmospheres. In addition, the CE marking, which ensures compliance with EU safety and environmental regulations must be adhered to. Standards such as SS-ISO 26142:2022 and EN 60079-29-1 provide guidelines for performance, ensuring that hydrogen detection systems operate with high precision and reliability in industrial settings.

3.2 Automatic quick-release valves

In hydrogen infrastructure, the ability to rapidly isolate or redirect gas flow during abnormal conditions is vital for maintaining both safety and operational control. Automatic quick-release valves play an essential role in this process by responding promptly to changes in pressure, sensor inputs, or emergency signals. These valves allow for the immediate shut-off or redirection of hydrogen in the event of a leak or system failure. This section discusses the key types of automatic quick-release valves, their functionalities, and their limitations, with a summary provided in Table 8.

Table 8

Table 8. Overview of automatic quick-release valves for hydrogen.

Solenoid valves are electrically operated devices designed to provide rapid shut-off or allow hydrogen flow in response to electrical signals from sensors detecting pressure, temperature, or leaks. These valves operate through a coil and plunger mechanism, where an electrical current triggers the valve to open or close. Due to their quick response times, solenoid valves are widely used in applications such as hydrogen fueling stations, emergency shut-off systems, and industrial hydrogen processes. However, solenoid valves require a stable power supply, which can limit their effectiveness in remote or off-grid applications. Additionally, they can be sensitive to extreme temperatures, potentially impairing performance under harsh operating conditions. Regular inspection and maintenance are necessary to ensure their long-term reliability in demanding environments (Shadvar and Rahman, 2024).

Ball valves, which can be either manual or automated, use a rotating ball with a bore to control hydrogen flow. When the valve is open, the hole aligns with the hydrogen flow path, allowing gas to pass through. Conversely, when the ball is rotated 90°, it blocks the flow, effectively closing the valve. Automated ball valves are especially effective in high-pressure hydrogen systems because they provide a tight seal and can handle pressures up to 1,000 bar (Li et al., 2023). These valves are commonly used in hydrogen storage and distribution systems, where rapid isolation of sections is essential during emergencies. While they are durable and require minimal maintenance, their response time tends to be slower than that of solenoid valves, potentially delaying critical actions in fast-paced environments (Dhavalikar et al., 2023).

Check valves are designed to prevent backflow in hydrogen pipelines. They ensure that the gas flows in a single direction and prevent contamination or pressure imbalances. These valves function by relying on a moving component, such as a disc, ball, or spring-loaded flap, which opens when hydrogen flows in the correct direction and closes automatically when reverse flow is detected. Check valves are widely used in hydrogen production and distribution systems. However, since they operate passively based on pressure differences, there is a delay in their closing action, making them less suitable for rapid shut-off applications. Check valves are also prone to wear, leakage, and flow instability over time, requiring regular inspection and maintenance to ensure they remain functional (Lang et al., 2024).

Pressure relief valves are key to preventing overpressure scenarios in hydrogen storage or pipeline systems, which could lead to equipment failure or catastrophic leaks. These valves are set to open at a predetermined pressure threshold and automatically close once the pressure normalizes (Kostival et al., 2013). Studies have shown that elevated temperatures can compromise the performance of pressure relief valves by causing them to open at lower-than-intended pressures and close at higher-than-normal pressures. This reduces their reliability under certain operating and environmental conditions (Jia et al., 2022).

Quick-connect couplings are designed to enable fast and secure connections for hydrogen transfer, such as between a storage tank and a vehicle. These couplings minimize leakage during connection and disconnection, which makes them essential for hydrogen fueling stations and mobile applications (Genovese et al., 2023). Quick-connect couplings require regular maintenance to prevent wear and tear, and improper handling can lead to leaks or accidental disconnections.

The various types of automatic quick-release valves play complementary roles in hydrogen infrastructure, each designed to address specific safety needs. While solenoid valves and ball valves are most suitable for rapid shut-off and isolation in industrial applications, check valves and pressure relief valves are necessary to ensure proper flow direction and prevent overpressure. Quick-connect couplings provide secure connections, ensuring safe hydrogen transfer. The choice of valve type depends on the specific requirements of the hydrogen infrastructure, including the operating pressure, environment, and application.

3.3 Emergency ventilation systems

Advancements in ventilation systems have provided various solutions to enhance safety in hydrogen environments, see Table 9. These systems are essential for preventing the accumulation of hydrogen to dangerous levels. It should be noted that ensuring consistent airflow and reliable hydrogen dispersal is a critical component of daily operational safety. Effective ventilation layouts, particularly in indoor or roofed settings, must address specific design elements. Roof vents, for instance, should be positioned at the highest points of an enclosure, as hydrogen is lighter than air and tends to accumulate near the ceiling. In situations where natural ventilation is insufficient, low-speed fans can be used to maintain airflow, especially in enclosed or low-flow areas. For critical systems, redundancy measures such as dual fans are often implemented to ensure uninterrupted operation during faults or outages. While the ventilation systems discussed here are primarily intended for general industrial use, they can be adapted to meet the needs of hydrogen infrastructure.

Table 9

Table 9. An overview of emergency ventilation systems and their reliability.

One of the simplest and most effective methods for hydrogen dispersal is natural ventilation, which relies on ambient airflow. This approach is most suitable for outdoor or semi-enclosed areas, where airflow is unobstructed. However, the performance of natural ventilation can be significantly influenced by weather conditions, such as wind speed, direction, and humidity. As a result, natural ventilation may not be effective in highly controlled spaces where these external factors are less predictable (Hajji et al., 2021). For confined spaces, forced or mechanical ventilation systems are often employed. These systems use fans to actively push hydrogen out of areas where it may accumulate (Ji et al., 2022). Mechanical ventilation systems are frequently integrated with hydrogen sensors that detect gas leaks and automatically activate the ventilation when hydrogen concentrations exceed a predefined threshold. These systems are generally reliable and are commonly used in environments such as laboratories or storage areas. However, their effectiveness is dependent on the continuous operation of both the fans and the sensors, which makes regular maintenance essential to ensure consistent performance.

In environments where the risk of ignition is a concern, explosion-rated ventilation systems are utilized (Cho et al., 2019). These systems incorporate fans and components specifically designed to minimize the risk of sparking, thereby preventing the ignition of hydrogen gas. Explosion-rated ventilation systems are important for enhancing safety in high-risk environments. Regular inspection and maintenance are necessary to ensure the continued functionality of these systems and to mitigate any potential hazards that may arise from wear and tear. More advanced approaches include smart ventilation systems that integrate real-time hydrogen sensors to continuously monitor gas concentrations. When hydrogen levels approach a predefined threshold, these systems dynamically adjust the ventilation by regulating exhaust fans, opening dampers, or optimizing airflow distribution. Once hydrogen concentrations return to safe levels, these systems can reduce ventilation intensity or deactivate excess airflow to optimize energy consumption while maintaining a safe operating environment (Ji et al., 2022). This approach ensures a balance between safety and energy efficiency.

Hybrid ventilation systems combine both natural and mechanical ventilation. It leverages the benefits of passive airflow and active mechanical control. These systems are used in environments where hydrogen levels fluctuate. They utilize natural ventilation when hydrogen concentrations are low and activate mechanical fans when higher concentrations are detected (Yahiaoui, 2020). This technology ensures optimal air exchange and helps maintain safe hydrogen levels in dynamic environments. In cases where active ventilation may not be feasible, passive ventilation systems act as an alternative (Barley et al., n.d.). These systems rely on the buoyancy of hydrogen, allowing the gas to rise and escape through pre-designed vents. Although passive ventilation can be effective in certain settings, its performance depends on external factors such as humidity, wind conditions, and temperature, which makes it less reliable for enclosed spaces. Despite this, passive ventilation systems remain an effective solution for environments where more complex ventilation options are not feasible.

In summary, the selection of an appropriate ventilation system for hydrogen environments depends on factors such as the size and layout of the space. Whether through natural, mechanical, explosion-rated, smart, hybrid, or passive systems, effective ventilation is essential for maintaining a safe working environment in hydrogen infrastructure. Regular inspection, maintenance, and adaptation of these systems are critical to ensuring their continued functionality and effectiveness.

3.4 Barrier systems

Barrier systems play an important role in hydrogen infrastructure by preventing material degradation through hydrogen diffusion, reducing leakage risks, and minimizing the impact of hydrogen fires or explosions (Rönnebro et al., 2022). These barriers can be broadly categorized into material-based barriers, which resist hydrogen diffusion and embrittlement, and physical barriers, which protect infrastructure and personnel from fires, explosions, and thermal radiation.

3.4.1 Material-based barrier systems

Material-based barriers are designed to limit hydrogen permeation and prevent degradation in infrastructure, including storage tanks and pipelines. These materials enhance structural integrity by blocking hydrogen diffusion, improving corrosion resistance, and preventing hydrogen-induced cracking, thereby reducing failure risks (Laadel et al., 2022). Several advanced materials have been developed for hydrogen infrastructure, including ceramic, metallic, carbon-based coatings, and polymer-based barriers. These materials are at different stages of application, with some already in industrial use and others still in the research and development phase.

Ceramic coatings, such as aluminum oxide (Al₂O₃), titanium aluminum nitride (TiAlN), and titanium carbide (TiC), have high resistance to hydrogen permeation while maintaining high mechanical strength and thermal stability. These coatings are used in hydrogen storage tanks, pipelines, and nuclear reactors (Wetegrove et al., 2023). It should be noted that their performance can degrade under long-term exposure to harsh environments (Wetegrove et al., 2023).

Metallic coatings, particularly nickel-based alloys such as Inconel and Hastelloy, provide moderate hydrogen resistance while maintaining structural integrity. These coatings are applied in medium-pressure hydrogen storage vessels, pipelines, and distribution systems. Despite their effectiveness, metallic coatings are prone to corrosion and require regular inspection and maintenance to ensure long-term reliability (Rönnebro et al., 2022). MAX phases are a class of materials that combine the properties of both metals and ceramics, making them uniquely suited for hydrogen applications. The name MAX comes from their general chemical formula, M_n+1AX_n, where M represents a transition metal (such as titanium or chromium), A is a group 13-16 element (such as aluminum or silicon), and X is either carbon or nitrogen (Tunes et al., 2022). This structure gives MAX phases the strength, oxidation resistance, and stiffness of ceramics while retaining the electrical conductivity, machinability, and thermal shock resistance of metals. MAX phase coatings, such as titanium silicon carbide (Ti₃SiC₂), have emerged as a promising solution for extreme environments due to their high corrosion and radiation resistance. Polymer-based barriers, including polyimides and fluoropolymers, exhibit flexibility and low permeability to hydrogen. They are suitable for low to moderate-pressure hydrogen distribution systems and insulation applications. These barriers can be applied in multilayer configurations to enhance protection. However, they are sensitive to extreme temperatures and chemical exposure, which can impact their durability (Sgambitterra and Pagnotta, 2024). Carbon-based coatings, such as graphene nanoplatelets and diamond-like carbon (DLC), have gained attention for their low hydrogen diffusivity, ability to prevent embrittlement, and added corrosion resistance. These coatings are particularly effective for high-pressure hydrogen pipelines and industrial hydrogen storage systems (Shi et al., 2022). However, the high cost of carbon-based coatings, along with the risk of delamination, present challenges for large-scale implementation. To address this, Mukherjee et al. (2019) identified plasma spraying as an effective technique for improving adhesion, enhancing durability, and reducing the likelihood of delamination. This makes carbon-based coatings more viable for hydrogen applications. Table 10 summarizes these barrier materials, along with their key features, applications, and reliability.

Table 10

Table 10. Overview of hydrogen barrier coatings, their key features, applications, and reliability.

3.4.2 Physical barrier systems

Physical barrier systems are essential safety elements in hydrogen infrastructure, providing both preventive and protective functions. While material-based barriers like coatings are designed primarily to prevent hydrogen permeation, physical barriers become especially critical in the event of an ignition or explosion. These structures are intended either to protect hydrogen equipment from external threats, such as fire or blast propagation, or to shield surrounding infrastructure, personnel, or the public from hazards originating within hydrogen systems.

Blast walls are designed to absorb and redirect shockwaves in the event of a hydrogen explosion. They are constructed from reinforced concrete, steel, or composite materials that can withstand high-impact forces (Linforth et al., 2023). Blast walls are commonly used in high-pressure hydrogen storage areas, refueling stations, and hydrogen production facilities where large quantities of hydrogen are handled under extreme conditions. The effectiveness of blast walls depends on their placement, thickness, and material composition. Recent studies have explored the effectiveness of blast walls in mitigating hydrogen explosion risks. Min utilized machine learning to predict hydrogen explosion waveforms with blast walls by training a neural network model on CFD simulation data. The study examined the effect of blast wall placement at distances of 2, 5, and 8 m from a 184-liter hydrogen storage vessel at 95 MPa. Pressure data were collected at multiple heights and distances to analyze overpressure and impulse distribution before and after the blast wall. The results showed that the presence of a blast wall increases overpressure in front of it while significantly reducing pressure behind it. The machine learning predictions indicated that a blast wall positioned at 5 m provided effective mitigation by balancing pressure redistribution while preventing excessive build-up (Min, 2024). Liu et al. investigated the protective effects of walls for containerized hydrogen fuel cell systems using CFD simulations (Liu M. et al., 2023). The authors also found that strategically placed walls can effectively block shock waves and flames, with optimal protection achieved at 5 m from the container and a height of 3 m.

Firewalls are another critical component of physical barrier systems, primarily designed to contain and prevent the spread of fire in hydrogen-related facilities. Similar to blast walls, these walls are made from non-combustible materials such as reinforced concrete, fire-resistant bricks, or fire-rated steel panels. The effectiveness of firewalls depends on fire resistance ratings (e.g., REI 120), material composition, and placement within the facility. A firewall rated REI 120 can withstand fire exposure for at least 120 min while maintaining stability, integrity, and insulation. Regulatory frameworks such as ISO 19880-1:2022 (hydrogen fueling stations) (ISO, 19880-1, 2020) mentions fire barriers (Clause 5.3.7.3) as a possible mitigation measure to reduce separation distances but does not specify exact reductions. In contrast, NFPA 2 (Hydrogen Technologies Code) (National Fire Protection Association, 2023) provides specific requirements and guidelines for the design and implementation of fire barriers. ATEX and IECEx explosion protection standards (IEC 60079-10-1, 2019) recognize fire barriers as a means to limit explosion risks in hazardous areas, however, do not specify exact firewall design requirements. Recent research has provided insights into optimal firewall design for hydrogen refueling stations, particularly in terms of height, width, and safety distances (Tian et al., 2024). Numerical simulations indicate that firewalls should be at least 2 m taller than the leakage hole to effectively block hydrogen jet flames and prevent backflow. Furthermore, the authors specified safe distances in front of and behind firewalls according to the storage pressure, see Table 11. The study also revealed a non-linear relationship between firewall width and hydrogen storage pressure, recommending a firewall width of 2.5 m for pressures of 35 and 45 MPa, and 3 m for pressures of 70 and 90 MPa. These findings emphasize the importance of strategic firewall placement to mitigate jet fire hazards and ensure safety in hydrogen infrastructure.

Table 11

Table 11. Safe distances around firewalls according to Tian et al. (2024).

In addition to conventional physical barriers, advanced containment structures such as explosion-resistant enclosures are used to further enhance safety. Explosion-resistant enclosures are particularly useful in hydrogen electrolysis plants and fuel cell manufacturing facilities, where hydrogen is stored and processed in enclosed environments (Magyari et al., 2022). Separation distances are also important in barrier systems. Regulatory standards such as NFPA 2 (hydrogen technologies code) and ISO 19880-1 specify minimum safety distances between hydrogen storage tanks, pipelines, processing units, etc. (Gordienko and Shebeko, 2022). The Hydrogen Technical Safety Assessment (H2-TSA 2023) are instructions developed to streamline safety assessments of hydrogen refueling stations in Sweden. It incorporates risk-based methodologies to establish separation distances and evaluate the need for protective barriers. Though currently focused on refueling stations, it provides a reference point for broader hydrogen infrastructure applications.

In a report by Marcus Runefors (2023) on suggested safety distances for hydrogen installations, a structured approach for determining safety distances required to protect people, buildings, and infrastructure from hydrogen-related hazards is provided. The key factors influencing these distances include hydrogen storage pressure (350, 500, and 1,000 bar), pipe diameter (8 mm), and leak size (small: 3%, medium: 10%, full rupture: 100%). The section categorizes safety targets, such as crowds, individual persons, air intakes, and difficult-to-evacuate buildings, and presents tables outlining the required distances based on these factors. For instance, crowds (SK1: protection class 1) require a clearance of 42–88 m, while single individuals (SK2) need 13–19 m. Air intakes, which pose a risk of hydrogen accumulation, require 8–36 m of separation, depending on pressure and isolation measures. The presence of an isolation system significantly reduces required distances by stopping the leak before it escalates. The section also includes formulas to adjust distances for pipe diameters other than 8 mm, ensuring applicability to different installation conditions. Explosion risks are primarily relevant in obstructed areas, where hydrogen accumulation could lead to higher overpressure effects. A section of the report also focuses on protecting hydrogen storage facilities from external hazards such as fires, vehicle impacts, and electrical discharges or heat sources. It outlines required safety distances based on the structural resistance of storage units. Low-resistance containers, such as composite tanks, require greater separation, whereas high-resistance containers, like thick steel tanks, require shorter distances. The report recommends minimum distances of 10 m from flammable material stockpiles, 4–13 m from industrial buildings, 2–9 m from office buildings, 3–12 m from vehicles, 1.5–10 m from forests, and 10–60 m from power lines and roads, depending on the risk level. Fire-rated barriers (E30, EI30, EI60) can significantly reduce or even eliminate required separation distances if they are independent of building structures. ​

4 Key research gaps in hydrogen infrastructure safety

Despite growing investment in hydrogen technologies, several research gaps persist that limit the safe deployment of hydrogen across the value chain. These gaps span infrastructure design, material performance, predictive modeling, human factors, and fire control. Addressing them is essential to reduce systemic risks and enhance the safety and resilience of hydrogen systems.

4.1 Technological and system-level safety gaps

The current hydrogen infrastructure exhibits notable gaps in the integration of advanced safety technologies. One key area for improvement is the limited adoption of real-time surveillance systems, such as the Internet of Things (IoT) and Artificial Intelligence (AI). These technologies hold considerable promise for enhancing leak detection and enabling predictive maintenance, yet their implementation in hydrogen applications remains constrained (Kumar et al., 2021). Digital twins, which could provide significant value by simulating potential system failures and providing real-time feedback, are still underdeveloped for hydrogen scenarios (El-Amin, 2024). This lack of integration may limit the ability to foresee and respond to potential risks effectively.

Additionally, cybersecurity remains a critical concern within the hydrogen safety infrastructure (Coppolino et al., 2023). As hydrogen systems become increasingly interconnected and reliant on digital technologies, vulnerabilities in cybersecurity may introduce indirect safety risks. The potential for cyberattacks or system failures highlights the necessity for further research into secure-by-design architectures, which would integrate safety measures from the outset of system development.

Ventilation strategies also require refinement, particularly in complex and confined spaces such as inter-floor voids (Ryu et al., 2023). Traditional airflow models often fall short in these settings, leading to inefficient hydrogen dispersal and increased risk. The current reliance on single-layer protection within safety systems further exacerbates this issue (Zhang D. et al., 2024). To address these concerns, innovations in autonomous fail-safe mechanisms, as well as the integration of redundant detection and shutdown architectures, are essential to prevent cascading failures and ensure the resilience of hydrogen infrastructure.

4.2 Material durability and long-term performance

Hydrogen embrittlement remains a significant challenge in the development of materials used in hydrogen infrastructure, particularly under high-pressure and cryogenic conditions (Liu J. et al., 2023). This is especially critical in materials used for pipelines and storage systems, where the long-term effects of hydrogen exposure have not been fully characterized. As a result, there are significant uncertainties regarding the ability of these materials to maintain their structural integrity and prevent leaks over time.

Moreover, the long-term behavior of insulation materials under hydrogen-rich conditions requires further investigation (Yatsenko et al., 2022). In particular, issues such as off-gassing and flammability need to be better understood, as these factors can pose safety risks over the lifespan of hydrogen infrastructure. The impact of aging infrastructure, especially when exposed to extreme environmental conditions, could exacerbate these concerns, highlighting the need for continued research into the durability and performance of materials used in hydrogen systems (Habib et al., 2023). Comprehensive studies are essential to ensure the reliable operation of hydrogen infrastructure and to mitigate risks associated with material degradation over time.

4.3 Risk assessment and predictive modeling

Risk assessment tools tailored specifically for hydrogen systems are still developing and lag behind those used in other high-risk industries. In particular, simulation models for the behavior of cryogenic hydrogen, especially in outdoor or geometrically complex environments, remain underdeveloped and lack sufficient validation (Mohammadpour and Salehi, 2024). This limitation poses challenges in accurately predicting hydrogen-related risks in these environments. Additionally, the simulation of blast waves and fireball behavior associated with hydrogen releases is constrained by a scarcity of experimental data, which undermines the reliability and accuracy of current predictive frameworks (Wang et al., 2023).

Simulation-based optimization methods have become increasingly important for improving safety and process efficiency in, for instance, hydrogen production systems. In the chemical process industry (CPI), modeling tools such as computational fluid dynamics (CFD), process hazard analysis (PHA), and dynamic process simulations are widely used to predict abnormal events and optimize reactor operations. Recent studies, including those by Akintola et al. (2025) on membrane reactor modeling for sustainable hydrogen production, Ghasemi et al. (2025) on simulation of biogas steam reforming, and Moravvej et al. (2025) on yttrium-modified nickel catalysts for green hydrogen production, demonstrate how simulation and multiobjective optimization approaches can enhance both performance and inherent safety. These works highlight the growing role of simulation-driven optimization in predicting potential failure scenarios and supporting safer hydrogen production pathways.

AI-based early warning systems have significant potential for real-time risk forecasting in hydrogen infrastructure. However, their adoption has been limited due to the absence of hydrogen-specific training datasets and standardized validation protocols (Patil et al., 2024). These gaps hinder the development of AI systems capable of reliably predicting and mitigating risks in hydrogen applications. Further research and data collection are critical to improving these predictive tools.

4.4 Human factors and operational reliability

Human reliability represents a critical aspect of hydrogen safety. Research into how operators make decisions under high-risk conditions, such as the presence of invisible flames or the potential for rapid ignition, remains scarce but is essential for the development of a robust safety culture. Understanding the cognitive and behavioral factors that influence operator decisions in these situations can greatly enhance the effectiveness of safety training programs and operational procedures (Patil et al., 2024).

Current risk models often fail to account for human factors such as stress-induced errors, deviations from established procedures, or lapses in situational awareness (Chauhan et al., 2023). These omissions limit the predictive accuracy of safety frameworks and may result in underestimating the likelihood of human error in hazardous situations. Integrating human factors into risk models is important for improving the overall reliability and safety of hydrogen systems. This ensures that both technological and human elements are adequately addressed in safety planning and response strategies.

4.5 Ignition, fire dynamics, and suppression

Ignition modeling for hydrogen systems, particularly under delayed or confined conditions, is an area of uncertainty. There are significant gaps in understanding the mechanisms of deflagration-to-detonation transitions (DDT), flame acceleration, and the impact of confinement on flame propagation (Rudy and Teodorczyk, 2020). These gaps hinder the accurate prediction of fire dynamics in hydrogen systems, and inconsistencies in reported detonation limits further complicate hazard assessment efforts.

Another area requiring more investigation is the phenomenon of localized oxygen enrichment during cryogenic hydrogen releases. Despite its potential to significantly influence ignition risk, this aspect is not well understood in current models of hydrogen behavior. A significant research gap also exists in the precise definition and measurement of detonation limits for hydrogen/air mixtures. While a lower detonation limit (LDL) of 18% is commonly reported, experimental evidence shows detonations can occur at concentrations as low as 11%, highlighting inconsistencies in the available data (SIS - Svenska Institutet för Standarder, 2022). The lack of a standardized measurement procedure, unlike well-established flammability limit tests, further complicates reliable hazard assessment. This gap emphasizes the need for systematic studies. Additionally, the suppression of hydrogen jet fires continues to pose a technical challenge. Existing extinguishing methods are often insufficient, particularly when faced with complex fire scenarios involving multiple leak sources. Multi-source leak situations exacerbate containment difficulties and highlight the need for further research into more adaptive and effective suppression systems. Improving suppression strategies is essential to mitigating fire risks and ensuring safety in hydrogen infrastructure (Wu et al., 2022).

5 Recommendations

This section provides recommendations aimed at improving hydrogen safety by prioritizing common risks, addressing urgent research gaps, and enhancing risk communication. The recommendations integrate information from the findings and aim to ensure the safe and sustainable expansion of hydrogen infrastructure.

5.1 Prioritizing the common risks in hydrogen safety

Hydrogen safety risks differ in severity, likelihood, and complexity, with some posing long-term operational challenges that require immediate intervention. While certain risks, such as small hydrogen leaks, may be frequent but manageable, others such as embrittlement-induced infrastructure failures, have the potential to cause catastrophic system failures. Based on the findings, three key risk areas have been identified as requiring urgent attention from academia, industry, and regulatory bodies:

• Hydrogen leaks and unintended releases represent the most persistent challenge across the hydrogen value chain and must be prioritized. Developing real-time monitoring systems, leak-resistant materials, and automated shutoff mechanisms to minimize the likelihood of uncontrolled hydrogen releases is recommended.

• High-pressure failures and over-pressurization risks remain a significant concern, particularly in storage systems operating at pressures of up to 1,000 bar. Over-pressurization can lead to tank bursts, pipeline explosions, and system-wide failures. This necessitates improvements in pressure relief mechanisms, material innovations and automated shutoff systems to prevent large-scale accidents.

• Hydrogen-induced material degradation, including hydrogen embrittlement, poses a long-term threat to infrastructure integrity. Embrittlement primarily affects metals, leading to loss of ductility and sudden failure. In polymers, hydrogen can cause swelling, blistering, or permeability changes, while ceramics may experience microcracking or loss of mechanical strength due to hydrogen ingress and thermal cycling. To address these challenges, research should prioritize hydrogen-compatible materials, advanced coatings, and real-time degradation monitoring. Standardized testing protocols across material classes are essential for comparability and reliability. Collaboration among researchers, engineers, and standards bodies will be key to bridging knowledge gaps and ensuring safe hydrogen infrastructure deployment.

Addressing these critical risks requires a three-pronged approach: (1) prevention through the use of advanced materials, (2) early detection via leak monitoring, and (3) containment through automated response systems that limit accident escalation.

5.2 Addressing research gaps

While advancements in hydrogen safety technologies are ongoing, several research gaps continue to hinder effective risk mitigation. The following areas require urgent attention to improve the safety, reliability, and scalability of hydrogen infrastructure:

• Advancements in predictive risk modeling and real-time monitoring can further improve early failure detection in hydrogen systems. Integrating AI-driven predictive maintenance and digital twin technology into hydrogen systems could support continuous risk assessment, early anomaly detection, and proactive mitigation strategies, contributing to greater system reliability and safety.

• An understanding of the ignition and combustion behaviour of hydrogen and its blends will be critical to the development of reliable safety strategies across diverse hydrogen applications. These challenges become even more pronounced in blended fuels and in constrained or cluttered environments where flame acceleration can lead to deflagration-to-detonation transitions (DDT). Additional concerns include the limited understanding of flame stability under varying pressures and turbulent flow. The absence of standardized detonation thresholds and validated measurement protocols further complicates safety design and emergency planning. Targeted research in these areas will enhance predictive modelling, inform risk-based design decisions, and support the development of more robust fire and explosion mitigation technologies.

• Improving hydrogen fire suppression and explosion mitigation techniques would further strengthen safety measures, particularly for hydrogen jet fires, which present unique challenges due to hydrogen’s nearly invisible flame and rapid flame propagation. Research into advanced fire suppression systems, self-extinguishing materials, and automated leak containment mechanisms could help reduce ignition risks and improve emergency response capabilities.

• Human factors in hydrogen safety remain understudied, particularly regarding operator decision-making, emergency response, and psychological stress in high-risk hydrogen environments. Research may focus on developing human reliability models, improving training programs, and assessing cognitive impacts on safety tasks. Understanding how human behavior influences risk mitigation will be essential for designing effective safety protocols.

5.3 Improving communication and education of risks, safety standards and regulations

Given the complexity of hydrogen safety risks, improving communication strategies is essential. This can be done through stronger collaboration between municipalities, industry, regulators, and researchers to ensure consistent interpretation and implementation of safety requirements. Joint workshops, shared databases, and cross-sector working groups can facilitate transparent information exchange and alignment on best practices across the hydrogen value chain. To enhance global hydrogen safety practices, the following measures are recommended:

• Standardized hydrogen safety frameworks should be developed to ensure consistent safety benchmarks across hydrogen applications. Regulatory bodies should harmonize guidelines for leak detection thresholds, ventilation system requirements, material durability standards, etc. Cross-sector collaboration between government agencies, research institutions, and industry stakeholders will be essential in developing globally accepted safety regulations.

• Stakeholder awareness and targeted education on hydrogen risks and safety measures should be prioritized to build confidence and ensure responsible adoption of hydrogen technologies. As hydrogen infrastructure expands, it is essential that key groups, including emergency responders, policymakers, urban planners, energy providers, and industrial operators, are equipped with accurate information about safe handling practices, emergency protocols, and risk mitigation procedures. It is also important to know what each stakeholder needs to learn and how to deliver the education. Governments and industry organizations should coordinate stakeholder-specific training and communication strategies. In later phases, broader public awareness efforts may be appropriate, particularly for communities located near hydrogen infrastructure, to ensure clarity around warning indicators, basic safety practices, and emergency response expectations.

6 Conclusion

This review explores hydrogen safety risks, reliability of mitigation strategies and research gaps. The goal is to provide a foundation to enhance emergency preparedness as hydrogen infrastructure expands within Sweden’s energy landscape.

In the study, the safety challenges at each stage, from production to end-of-life has been systematically analyzed. In hydrogen production, leakage incidents linked to electrolysis, steam methane reforming, and gasification demonstrate the necessity of stringent monitoring, robust containment measures, and improved process control to prevent explosions and chemical hazards. Storage challenges primarily revolve around high-pressure containment, cryogenic handling, and material degradation, which necessitates advanced barrier materials and reliable pressure relief mechanisms. Distribution risks highlight pipeline integrity issues, embrittlement concerns, and accident-prone transit conditions, which must be mitigated through reinforced infrastructure and enhanced leak detection technologies. Hydrogen utilization in fuel cells, industrial processes, and refueling stations introduces risks associated with fire, static ignition, environmental contamination, and potential external attacks or sabotage. Finally, decommissioning of hydrogen infrastructure requires well-defined end-of-life protocols, proper purging procedures, etc. to prevent accidental releases. These risks emphasize the need for stringent operational safety protocols, including protections against external attacks, to ensure the safe and resilient deployment of hydrogen technologies.

This review has also examined key safety measures such as leak detection systems, automatic quick-release valves, emergency ventilation systems, and barrier technologies. Each of these approaches contributes to reducing risks, but their effectiveness depends on proper implementation, regular maintenance, and advancements in technology. Several technologies are available for hydrogen leak detection systems including catalytic bead, electrochemical, ultrasonic, semiconductor sensors, etc., each with specific advantages and limitations. While these technologies improve hydrogen monitoring, challenges such as sensor degradation and cross-sensitivity, must be addressed to enhance their reliability. Similarly, automatic quick-release valves provide rapid shutoff mechanisms but require periodic testing and backup systems to prevent failures in high-risk environments. Emergency ventilation systems, including natural, mechanical, and hybrid solutions, provide essential dispersion of hydrogen to prevent hazardous accumulation. However, their effectiveness is often influenced by environmental conditions, system placement, and real-time responsiveness to hydrogen releases. Barrier systems, including material-based coatings and physical-based systems such as firewalls, serve as a final line of defense against leaks, fires, and explosions, respectively. While ceramic, polymer-based, and metallic coatings have shown promise in preventing hydrogen embrittlement and diffusion, further research is needed to improve long-term performance and cost-effectiveness. Additionally, firewalls and blast-resistant enclosures must be strategically designed to mitigate worst-case scenarios effectively.

The review has also highlighted research gaps, particularly in areas such as predictive analytics for early failure detection, human reliability assessments, detonation, and fire suppression technologies. Addressing these gaps will require interdisciplinary collaboration among policymakers, researchers, and industry stakeholders to develop standardized frameworks, safety benchmarks, and best practices for hydrogen applications. Moreover, effective risk communication and stakeholder awareness initiatives are important in fostering societal trust and ensuring the safe deployment of hydrogen technologies. Establishing globally recognized safety standards and harmonized regulatory guidelines will help facilitate the integration of hydrogen into the various sectors.

In conclusion, it is undeniable that hydrogen presents immense potential in advancing clean energy solutions, however, similar to other fuels, it is equally important to address its safety challenges to ensure its safe and sustainable integration into energy systems. The future work will focus on an overview of hydrogen standards and regulations to identify gaps.

Author contributions

RM: Writing – original draft, Methodology, Investigation, Writing – review and editing, Funding acquisition, Conceptualization. AC: Formal Analysis, Methodology, Writing – review and editing. SA-O: Investigation, Methodology, Writing – review and editing. CW: Resources, Writing – review and editing, Supervision, Methodology. MF: Resources, Project administration, Investigation, Writing – review and editing, Methodology, Supervision, Funding acquisition, Writing – original draft, Conceptualization.

Funding

The author(s) declared that financial support was not received for this work and/or its publication.

Acknowledgements

The authors extend their appreciation to the Swedish Civil Contingencies Agency (MSB) for funding this work under the research call for knowledge overviews in civil protection and preparedness. The research number is MSB 2024-09009.

Conflict of interest

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Generative AI statement

The author(s) declared that generative AI was not used in the creation of this manuscript.

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