Hydrogen Purity Standards
Hydrogen purity is specified as a minimum hydrogen mole fraction together with limits on named contaminants; the production route determines which contaminants are credible in the first place.
- Purity grades state both a hydrogen fraction and per-species contaminant limits.
- Moisture is the dominant contaminant in PEM output; caustic aerosol is not present.
- Purity requirements are set by the downstream duty, not by the generator alone.
Mechanism
Contaminants enter a gas stream from the feedstock, the electrolyte, the wetted materials and the ambient environment. Removing a contaminant source at the cell is more robust than removing it downstream.
PEM purity
Because a PEM cell has no liquid electrolyte inventory, the specification focuses on residual water vapour and trace species from construction materials. Deionised feed water keeps dissolved solids out of the stack.
Production
Purity is maintained by feed-water treatment, resin-based polishing, gas–liquid separation and drying, each sized to the nominal output and duty cycle.
Industrial and consumer applications
Industrial combustion duty and consumer modality duty specify different purity envelopes. Both are stated as engineering requirements, not as claims about results.
Reference material only. CE Global publishes hydrogen production and PEM electrolysis engineering information. Nothing here is a medical, health, performance, emissions or fuel-saving claim.