The hydrogen fuel quality is critical to the efficiency and longevity of fuel cell electric vehicles (FCEVs), with ISO 14687:2019 grade D establishing stringent impurity limits. This study compared two different sampling techniques for assessing the hydrogen fuel quality, focusing on the National Physical Laboratory hydrogen direct sampling apparatus (NPL DirSAM) from a 35 MPa heavy-duty (HD) dispenser and qualitizer sampling from a 70 MPa light-duty (LD) nozzle, both of which were deployed on the same day at a local hydrogen refuelling station (HRS). The collected samples were analysed as per the ISO 14687:2019 contaminants using the NPL H₂-quality laboratory. The NPL DirSAM was able to sample an HD HRS, demonstrating the ability to realise such sampling on an HD nozzle. The comparison of the LD (H₂ Qualitizer sampling) and HD (NPL DirSAM) devices showed good agreement but significant variation, especially for sulphur compounds, non-methane hydrocarbons and carbon dioxide. These variations may be related to the HRS difference between the LD and HD devices (e.g., flow path, refuelling conditions and precooling for light duty versus no precooling for heavy duty). Further study of HD and LD H₂ fuel at HRSs is needed for a better understanding.

Taking spot samples at hydrogen refuelling stations (HRSs) and performing offline analysis in laboratories is currently the only way to achieve hydrogen fuel compliance at HRS (meet the ISO 14687:2025 standard or EN 17124:2022 in Europe). Currently, different sampling strategies are defined in ISO 19880-9:2024 (Annex A–C) and implemented in different parts of the world (EU, Japan, USA). The differences in conducting the sampling potentially influence the hydrogen samples; therefore, there is a need to compare the different sampling strategies. Comparative sampling studies are required to evaluate the equivalence of sampling methodologies and support the standardisation of hydrogen fuel sampling. This study provides a systematic comparison of five European sampling systems with different sampling strategies under real and defined HRS operation conditions. The results show that the issue of representative sampling is more complex than initially assumed and that there is an interdependence of sampling device and HRS configuration, respectively.

Hydrogen sampling is an essential part of ensuring reliable and accurate hydrogen fuel quality for expanding heavy-duty vehicle applications. Hydrogen sampling at refuelling stations is highly sensitive to operational conditions, especially temperature, pressure, storage homogeneity, and nozzle-purging procedures. The direct sampling method operates with a hydrogen fuelling station in maintenance mode and requires that parameters be set properly. This study investigated the impact of temperature, pressure, storage bank selection, and venting on hydrogen sample quality. This study shows that hydrogen sampling at refuelling stations is strongly influenced by operational parameters, with temperature and pressure mainly affecting the water content while other contaminants remain largely stable; storage bank composition and insufficient nozzle purging can also significantly bias results through contamination or non-representative sampling. To ensure reliable measurements, this study recommends conducting sampling under representative operational conditions, including matching the delivery temperature and nominal delivery pressure, verifying storage homogeneity, and applying adequate nozzle-purging procedures. However, further validation across different systems is still needed.

This study investigates how hydrogen refuelling station (HRS) operating parameters influence the representativeness of hydrogen fuel samples collected during parallel sampling events. Parallel sampling methodology is regularly used in Europe because it can be performed during normal vehicle refuelling with minimal disruption, but uncertainty remains regarding the effects of refuelling protocol, flow profile, or storage-bank usage. Experiments were conducted at the ZBT test HRS using the HySaM sampling system and at operating European HRS using the NPL ParSAM. Controlled comparisons were performed between several flow-rate profiles, while comprehensive impurity analysis was performed against ISO 14687:2025 requirements. Under controlled conditions, the refuelling protocol (excluding temperature and storage bank) and flow-rate profile had limited influence on most contaminants, whereas water showed the greatest variability and requires further investigation. However, repetitive sampling at normally operating HRS revealed larger differences for several species, including nitrogen, oxygen, argon, methane, carbon dioxide and sulphur, indicating that factors beyond protocol parameters tested in this study and nominal flow rate, such as storage-bank switching, flow path, and station hardware, may affect measured composition. Modelling indicates that the filling rates of the sampling cylinder and FCEV may diverge depending on the sampling-system strategy, highlighting the need for further improvements. The results show that parallel sampling may represent the fuel delivered during a specific refuelling event (if the filling rate of the cylinder and FCEV are sufficiently similar). However, parallel sampling may not fully represent the overall HRS and all operating conditions. Further research involving a broader range of HRS technologies and operating conditions may lead to validation and standardisation of the finding and possibly dedicated sampling protocols.