Oxygen plant comparison

PSA vs Cryogenic Oxygen Plant: Which to Choose

Oxygen & PSA·7 min read·Updated 13 Jul 2026

The two ways to make oxygen from air are PSA (pressure-swing adsorption) and cryogenic air separation. PSA generates oxygen on site at moderate purity and low cost; cryogenic plants deliver the highest purity and liquid oxygen at larger scale. The right choice depends on your purity, volume and whether you need liquid.

The short answer

A PSA oxygen plant uses adsorbent beds (zeolite molecular sieve) to pull oxygen out of compressed air on site, typically at 93–95% purity — ideal for steady, small-to-medium demand where on-site generation beats buying cylinders. A cryogenic air-separation unit (ASU) cools and distils air to produce 99.5%+ oxygen and liquid oxygen, and suits large, continuous demand or any need for liquid supply.

Side-by-side comparison

FactorPSA oxygen plantCryogenic ASU
Purity93–95%99.5% and higher
Product formGas (on site)Gas + liquid oxygen
Best scaleSmall–mediumMedium–very large
On-site generationYes — no cylinder logisticsYes, but larger plant/utilities
Start-up / turndownFast start, easy turndownSlower start, best run continuously
Cost per Nm³Low at moderate scaleLow at large scale
Footprint & complexityCompact, simplerLarger, more complex

How to choose

  • ✓Need 99.5%+ purity or liquid oxygen? → cryogenic ASU.
  • ✓Steady on-site demand at 93–95% purity? → PSA plant, to stop paying for cylinders and delivery.
  • ✓Large, continuous, round-the-clock demand? → cryogenic, which is most economical at scale.
  • ✓Variable or seasonal demand with fast on/off? → PSA turns down and restarts easily.

Many sites use a mix — on-site PSA for base process demand, plus cylinders or bulk liquid for peaks and high-purity needs.

Frequently asked questions

A PSA plant adsorbs oxygen from compressed air on site at 93–95% purity; a cryogenic air-separation plant distils cooled air to make 99.5%+ oxygen and liquid oxygen at larger scale. PSA is simpler and on-site; cryogenic is higher purity and can make liquid.
An adsorption oxygen plant is another name for a PSA (pressure-swing adsorption) oxygen plant — it uses zeolite molecular-sieve beds that adsorb nitrogen and let oxygen pass, concentrating oxygen to about 93–95% purity on site.
It depends on scale. PSA is very economical for steady small-to-medium on-site demand; cryogenic becomes the most economical option at large, continuous volumes and when liquid oxygen is needed.
Standard PSA oxygen plants deliver about 93–95%. Reaching 99.5%+ typically requires a cryogenic air-separation plant or additional purification; for most cutting, furnace and effluent uses, 93–95% is sufficient.
Neither is universally better — PSA wins for compact on-site generation at moderate purity and demand, cryogenic wins for high purity, liquid oxygen and large continuous volumes. The right choice follows your purity, scale and liquid needs.

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Choosing an oxygen plant?

IIGAS builds both PSA and cryogenic oxygen plants. Tell us your purity, volume and site and we’ll recommend and engineer the right one.