Hydrogen Purity Grades
Hydrogen purity grades are minimum quality specifications set by end use; for hydrogen purity, ISO 14687 defines them, with Grade D for PEM fuel-cell road vehicles requiring at least 99.97 %.
In plain terms
"Pure hydrogen" has no single meaning. A fertiliser plant, a gas turbine and a fuel-cell truck tolerate very different impurities. ISO 14687 sets the minimum quality for each use. The 2025 edition replaced the 2019 edition.
The main grades in ISO 14687:2025:
| Grade | End use |
|---|---|
| A | Other gaseous applications |
| D | PEM fuel cells in road vehicles |
| E | PEM fuel cells in stationary appliances |
| F-1, F-2 | Hydrogen combustion engines (new in 2025) |
Typical range
Grade D requires a hydrogen fuel index of at least 99.97 %, so no more than 300 µmol/mol of total impurities, as applied in California's hydrogen fuel regulations. The standard also sets limits for individual impurities; for those tables, use the standard itself.
Why it moves LCOH
Electrolytic hydrogen starts clean: its main impurities are water and oxygen, which deoxo and drying remove. A stricter grade means a deeper dew point, more purge loss and more analysis. For ammonia or refinery offtakers, a lighter spec can trim gas conditioning cost and losses.
Common mistake
Related terms
Sources
- ISO 14687:2025 Hydrogen fuel quality: Product specification, International Organization for Standardization, 2025
- Hydrogen fuel regulations (Grade D hydrogen fuel index), California Department of Food and Agriculture, Division of Measurement Standards, 2024