How do I size a nitrogen generator, and should I choose PSA or membrane technology?

Start from purity, then size on peak flow.

Membrane generators typically deliver 95–99% purity and suit blanketing, purging, packaging atmosphere control and general lab use where 99% is sufficient — they are compact, need no regeneration cycle and tolerate varied demand.

PSA generators reach 99.9–99.999% purity and are the correct choice for LC-MS, GC carrier and make-up gas, sample evaporation, glove boxes and instruments sensitive to moisture or oxygen.

For sizing, add together the peak consumption of every connected consumer (do not use average flow), add a 20–30% margin, then correct for site altitude, ambient temperature and required dew point. If your demand fluctuates widely, a smaller generator plus buffer storage is usually more economical than a larger generator idling.