D5 -- Guidelines for representative sampling at HD-HRS, including the minimum sample size, the filling pressure and the evaluation of the uncertainty (target 10 % relative)

Representative hydrogen sampling is essential to ensure accurate fuel quality assessment, as even trace contaminants can negatively affect fuel cell performance and durability. The MetHyTrucks project demonstrated that reliable sampling is achievable, with most gaseous components meeting the ±10% uncertainty target, although challenges remain for oxygen measurements.For water amount fraction, only one sampling system met the performance objective, highlighting the importance of appropriate cylinder treatment and effective flushing procedures. Additional work is needed to improve underperforming systems and ensure consistent trueness.Further investigations are also required to assess the impact of HRS operating conditions, particularly when using maintenance mode for direct sampling, as well as to better understand the behaviour of trace sulphur compounds and their stability in sampling cylinders. For particulate matter, limited testing conditions currently prevent a full understanding of variability sources. This deliverable provides practical guidelines and recommendations for achieving representative hydrogen sampling at HD-HRS, based on the key findings of the MetHyTrucks project.Overall, the study emphasizes the need for validated sampling systems and robust procedures to ensure representative sampling and reliable hydrogen quality measurements.