USP Oxygen 93 Percent monograph

What the monograph covers

The USP-NF monograph Oxygen 93 Percent defines the gas made from ambient air by the molecular sieve process, the adsorption technology used in PSA plants, which push compressed air through sieve beds. It sets the oxygen content at 90.0% to 96.0% by volume. Only the definition is public; the tests are in the subscription text of the USP-NF.

It is a separate monograph from USP Oxygen, which requires not less than 99.0% oxygen. A specification that writes only USP Oxygen therefore does not cover oxygen 93.

Status

The definition was read at the USP-NF DOI page on 22 October 2026. The tests and acceptance criteria are only in the subscription text, so check them in a current licensed copy of the USP-NF before writing them into a specification.

How oxygen 93 is defined elsewhere

What it means for a hospital or designer

• The US and European monographs give the same 90.0% to 96.0% range, but they are separate texts with their own tests; a specification should name the pharmacopoeia that applies in the country of use.
• The WHO technical specifications for PSA oxygen plants (8 June 2020) asked for medical oxygen 93% ± 3 and an alarm when the oxygen concentration falls below 90%.
• For free, published impurity limits, the International Pharmacopoeia gives them for Oxygen 93%, for example carbon dioxide at most 300 ppm and carbon monoxide at most 5 ppm (V/V).

Related standards

• Ph. Eur. 2455: Oxygen (93 per cent).
• WHO technical specifications for PSA oxygen plants (2020).
• Ph. Eur. 3098: Oxygen (98 per cent), for two-stage plants.

ULTRAOX SC and ST PSA plants from Ultra Controlo state a purity of 94% (±1%) in their datasheets, which lies inside the 90.0% to 96.0% range of the monograph.