Oxygen 93 vs 99: Understanding PSA and Cryogenic Medical Oxygen

What the two numbers mean

Traditional medical oxygen from cryogenic air separation, supplied as liquid or in cylinders, has a purity of at least 99.5% in the pharmacopoeia monograph for oxygen. PSA, or pressure swing adsorption, plants separate nitrogen from air with molecular sieves and produce oxygen-enriched air in the range of 93%, with the balance mostly argon and a small amount of nitrogen.

Argon is not a contaminant here: it is similar in size to oxygen and is not removed by the sieve, which is why PSA purity levels off around 93-95%. The MIL's oxygen concentrators produce 93-95% oxygen-enriched air, and according to the manufacturer this gas may replace medical oxygen provided all the required parameters are met.

For a buyer, the practical consequence is that the same pipeline can carry either gas, but labelling, documentation, analyser settings and release procedures differ. The facility's pharmacy must know which quality it is receiving at each outlet.

Pharmacopoeia monographs: oxygen 93 USP and Ph. Eur.

Major pharmacopoeias include a separate monograph for oxygen produced by this method. The United States Pharmacopeia has a monograph titled oxygen 93 percent, and the European Pharmacopoeia has a monograph for oxygen 93 per cent. Each sets identity, purity and permitted impurities such as carbon monoxide, carbon dioxide and moisture.

Always check the current edition applicable in your jurisdiction. Whether a monograph is legally binding depends on national rules, and the UAE position should be confirmed with the relevant health authority rather than assumed.

Clinical acceptance and where PSA oxygen is used

PSA oxygen is widely used for pipeline supply in hospitals where logistics for liquid oxygen are difficult, and for emergency and surge capacity. Clinical suitability for a given therapy is a decision for the clinical team and pharmacy. Certain applications, such as high-precision anaesthesia mixtures or neonatal use, may require specific review of the oxygen source.

For critical care and anaesthesia, check that the gas analyser alarms and the monitors at the point of use are set up with the actual concentration in mind, and make sure staff know that the delivered fraction will be slightly lower than 100% even at maximum setting.

Training matters: nurses and technicians who move patients between areas should understand that oxygen from a PSA source is delivered through the same outlets and flowmeters as any other medical oxygen.

Purity monitoring and plant design

A reliable plant includes an oxygen analyser on the product line, automatic diversion of off-specification gas to vent, and an alarm and log. Intake filters, compressors, dryers and sieves have to be maintained so that purity remains within the specification; see oxygen concentrator plant maintenance.

Backup supply is essential. Combine the plant with a cylinder manifold or other source for continuity, and size it based on a proper demand calculation; our guide to hospital oxygen consumption calculation explains the method.

Document the purity trend. A slow decline over months is an early warning that sieves, filters or the compressor need attention before an alarm is raised.

Questions to settle before you buy

Ask the supplier which monograph the gas is designed to meet, what analyser is included, what happens when purity drops and what documentation accompanies commissioning. Ask your authority whether on-site 93% oxygen can be used as a medicinal gas in your facility and under which conditions.

Beckfinity represents MZ Liberec in the UAE. Contact our specialists with your demand profile and regulatory questions for a technical consultation.