Why hydrogen purity matters for your application
- Why hydrogen purity directly impacts system performance, product quality and operational reliability
- How hydrogen purity is measured
- How different applications have varying tolerance to impurities
- Where hydrogen impurities come from throughout production, handling and transport
- Why purity risks are often overlooked
- What to consider when aligning hydrogen purity with your application
Hydrogen is often viewed as a clean, versatile energy source, but not all hydrogen is the same. The composition of hydrogen can vary depending on how it’s produced, handled and delivered, and these variations can have a direct impact on how it performs in your application.
While many organisations are focused on securing hydrogen supply and managing costs, purity is an equally important consideration. It can influence system performance, product quality, equipment lifespan and operational reliability. In some cases, even trace levels of impurities can lead to measurable losses or long-term damage.
Understand what level of purity your application requires to get the most value from hydrogen integration.
Not all hydrogen is the same
Hydrogen is not a uniform product. Its purity depends on its production pathway and what happens to it afterwards.
Different production methods introduce different impurities. For example, hydrogen produced from fossil fuels may contain trace amounts of carbon monoxide or sulfur compounds if not fully purified. Hydrogen from electrolysis is typically higher purity, but can still contain moisture or oxygen depending on the system and operating conditions.
Once produced, hydrogen may be compressed, stored, transported or transferred between systems. Each of these steps creates opportunities for contamination – often at very low levels, but still enough to matter in sensitive applications.
The result is that two hydrogen supplies labelled with similar purity levels can behave very differently in practice.
How is hydrogen purity measured?
Hydrogen purity is typically measured as both an overall percentage (e.g. 99.97%) and a detailed impurity profile. This means looking beyond the hydrogen concentration itself and measuring trace contaminants such as oxygen, nitrogen, carbon monoxide, carbon dioxide, methane, moisture and sulfur compounds, often measured in parts per million (ppm) or lower.
Common methods include:
Gas chromatography (GC): Separates and measures gases such as oxygen, nitrogen, carbon monoxide and carbon dioxide.
GC with specialised detectors (e.g. PDHID): Enables highly sensitive detection of trace impurities at very low levels.
Mass spectrometry (MS): Identifies and quantifies a wide range of impurities with high precision.
Cavity ring-down spectroscopy (CRDS): Used for high-sensitivity measurement of gases such as moisture, CO₂ and methane.
Targeted sensors: Monitor specific contaminants such as oxygen or moisture in real time.
The method used depends on the application, required detection limits and specific impurities that need to be controlled.
How impurities impact different applications
Hydrogen purity requirements depend on how it is used. Some applications are highly sensitive to contamination and rely on a consistent supply of pure hydrogen, while others are more tolerant. Consider the following.
| Application | Typical purity requirement | Notes |
|---|---|---|
| Fuel cells (e.g. buses, mobility) | ≥99.97% (ISO 14687) | Fuel cells (mobility, PEM): ≥99.97% (ISO standard), often higher (up to 99.999%+) to support performance and longevity. |
| Industrial feedstock (ammonia, refining) | ≥99.0–99.9% | Process-dependent |
| Combustion (boilers, turbines) | ≥98–99.5% | Sensitive to moisture and air ingress |
| Electronics/ semiconductor manufacturing | ≥99.999%+ | Ultra-high purity requirements |
| Advanced manufacturing (e.g. diamond growth) | ≥99.9999% | Very high sensitivity to impurities such as nitrogen |
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Our free guide can help you learn how to choose the right hydrogen purity for your use case. For a more detailed breakdown of key contaminants and supply choices, check out Endua's hydrogen purity cheat sheet.
1. Fuel cells
In fuel cell applications, such as buses, heavy vehicles or backup power systems, purity is critical. Trace amounts of carbon monoxide or sulphur compounds can poison catalysts, leading to rapid performance loss and irreversible damage. Moisture can also affect system efficiency and durability over time.
2. Industrial feedstock
Industrial processes such as refining or ammonia production are generally more tolerant, but impurities can still affect reaction efficiency, product yield and downstream processing. In these environments, stable, predictable gas composition often matters just as much as absolute purity.
3. Combustion
Combustion-based applications, including boilers and turbines, can operate with lower purity hydrogen. However, variations in gas composition (particularly moisture or oxygen levels) can influence combustion stability, efficiency and system tuning.
4. Advanced manufacturing
At the highest end of the spectrum, advanced manufacturing processes like semiconductor fabrication or diamond growth require ultra-high purity hydrogen. In these cases, even trace levels of gases like nitrogen or oxygen can affect material quality and final product outcomes.
What are common hydrogen impurities and where do they come from?
Before we look at how impurities are introduced across the supply chain, it can helpful to understand the most common contaminants and how they can have an impact.
| Impurity | Impact |
|---|---|
| Carbon monoxide (CO) | Poisons catalysts, especially in fuel cells |
| Carbon dioxide (CO₂) | Reduces efficiency and can affect reactions |
| Nitrogen (N₂) | Dilutes hydrogen, reducing energy content |
| Oxygen (O₂) | Safety risk and can affect performance |
| Water (H₂O) | Causes corrosion, freezing and efficiency loss |
| Sulfur compounds (e.g. H₂S) | Causes irreversible catalyst damage |
| Ammonia (NH₃) | Can damage fuel cells and downstream systems |
These impurities can be introduced at multiple stages across the hydrogen value chain and are typically present at very low levels, but their impact can depend on the application and sensitivity of the system. Understanding where they originate can help you better manage risk.
1. Production method plays a major role
Fossil fuel-derived hydrogen (such as steam methane reforming) can introduce carbon monoxide, carbon dioxide and sulphur compounds if not fully removed.
Alkaline electrolysis systems may introduce moisture or trace electrolyte carryover.
PEM electrolysis systems typically produce high-quality pure hydrogen gas, though effective drying and controlled operating conditions remain important to maintain purity.
2. Storage and transport introduce another layer of variability
Compression, pipelines and storage vessels can allow small amounts of air ingress, introducing nitrogen and oxygen.
Handling steps such as decanting, unloading or transferring hydrogen between systems can also introduce contaminants.
Moisture contamination is a common risk during these stages, particularly if systems are not fully sealed or dried.
3. System design and operation also influence purity
Leaks, seal degradation or purge gases can alter composition over time.
Inconsistent operating conditions can result in fluctuations in gas quality.
Why purity risks are often overlooked
Impurities often exist at very low concentrations, measured in parts per million or even lower, which makes them easy to overlook. However, in many systems, these trace levels are enough to affect performance or longevity.
There can also be a disconnect between procurement and operational requirements. Hydrogen supply may meet a general specification, but still fall short of what a specific process or system needs to operate optimally.
As hydrogen adoption expands across industries, aligning purity specifications with real application requirements is increasingly important.
What to consider when specifying hydrogen requirements
Selecting the right hydrogen supply starts with understanding how it will be used and what level of purity your application requires.
Rather than relying on a single purity figure, consider the factors the following which can influence performance and risk:
Equipment sensitivity – what impurities can your system tolerate?
Application requirements – does purity affect efficiency, yield or product quality?
Production method – different pathways introduce different impurities.
Storage and handling – more steps increase contamination risk.
Operating conditions – temperature and environment can influence performance.
Standards and compliance – are there specific industry requirements to meet?
Monitoring and verification – how will purity be measured and maintained?
The benefits of on-site hydrogen generation for a more controlled approach
Variations in purity mean that not all hydrogen delivered to site will meet the expectations of pure hydrogen gas without additional control measures. One way to reduce purity-related risks is by generating hydrogen on-site.
By producing hydrogen where it is used, organisations can reduce exposure to contamination during transport and handling. It also provides greater visibility and control over system performance and output quality.
This approach can be particularly valuable for applications that require consistent or high-purity hydrogen, or where reliability and operational continuity are critical.
Did you know: Endua’s PEM electrolysers enable reliable, on-site hydrogen generation on demand. Learn more about our all-in-one, safe, compliant system.
Get the right purity for your application
Hydrogen purity requirements aren’t one-size-fits-all. They can vary significantly depending on the application, process and level of sensitivity to specific impurities.
Overlooking these differences can lead to reduced efficiency, unexpected maintenance issues or compromised product quality. But by understanding what level of purity your application actually requires, and what can influence it, you can make more informed decisions around supply, system design and long-term performance.
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To simplify these insights, we’ve created a quick reference guide that outlines typical hydrogen purity requirements by application and key impurities to be aware of.
Download our free cheat sheet: How to choose the right hydrogen purity for your use case.
Access your copy to quickly identify:
- the typical purity levels required for your application
- which impurities to look out for
- how purity can impact performance and outcomes
Need confidence in your hydrogen purity? Get in touch with Endua to discuss how our PEM electrolysers can deliver consistent, high-quality hydrogen where you need it.
FAQs
Is higher purity hydrogen always worth the cost?
Achieving higher purity hydrogen can increase costs through additional purification, monitoring and system maintenance. However, in many applications, the cost of using lower purity hydrogen can be significantly higher. Impurities can lead to reduced efficiency, damaged equipment, failed reactions or compromised product quality.
For systems that are sensitive to contamination, investing in higher purity hydrogen (or better control over supply) can help reduce downtime, performance losses and long-term reliability issues. The right balance depends on how critical purity is to your process and the potential impact if it’s not maintained.
What impurities are most harmful in hydrogen?
The most harmful impurities depend on the application, but carbon monoxide, sulphur compounds and moisture are among the most critical for fuel cells. In high-precision manufacturing, gases like nitrogen and oxygen can also have a significant impact.
What hydrogen purity do fuel cells require?
Fuel cells, particularly PEM systems, typically require very high purity hydrogen (around 99.97% or higher). They are highly sensitive to impurities such as carbon monoxide and sulphur, which can damage catalysts and reduce performance.
Does hydrogen lose purity during transport?
Hydrogen can be affected during transport and handling. Processes such as compression, storage and transfer can introduce small amounts of contaminants like air or moisture, particularly if systems are not fully sealed or controlled.