Is measuring oxygen purity alone enough?

AIGA 113/20 adds continuous carbon dioxide, carbon monoxide and moisture analysis to the double oxygen analysers, while the International Pharmacopoeia (2025) asks for continuous oxygen monitoring and a production process validated against the Oxygen 93% limits.

How are the CO and CO2 alarms checked?

AIGA 113/20 lists the carbon monoxide and carbon dioxide high level alarms and their automatic shutdown among the safety checks, which could be made with calibration gases for the detectors.

Should a PSA plant monitor CO, CO2 and moisture online?

Q: Should a PSA oxygen plant have online analysers for impurities such as CO, CO2 and moisture, not just oxygen purity?

AIGA 113/20, adopted from EIGA Doc 195, lists carbon dioxide, carbon monoxide and moisture for continuous monitoring in an oxygen 93 plant, with analysers that can close the main shut-off valve, and leaves oil, nitrogen oxides and sulfur dioxide to local rules and the site's risk analysis.

Should a PSA oxygen plant have online analysers for impurities such as CO, CO2 and moisture, not just oxygen purity?

What AIGA 113/20 monitors and how often

Parameter	Interval in AIGA 113/20, Table 5
Oxygen assay	Continuous, with double analysers
Carbon dioxide	Continuous
Carbon monoxide	Continuous
Moisture	Continuous; the table notes that an increase in moisture would lead to accelerated damage of the adsorbers
Sulfur dioxide	Continuous monitoring can be required by local regulations or as a result of the risk analysis (air intake contamination); testing at commissioning and after any modification or significant intervention is mandatory
Nitric oxide and nitrogen dioxide, oil	Continuous monitoring can be required according to local regulations and as a result of the risk analysis; testing at commissioning and after any modification or significant intervention is mandatory
Particle filter differential pressure, oxygen in the room air, oxygen 93 flow, compressor gas temperature	Continuous, as critical control points

Among the components of a typical oxygen 93 supply system, the same document lists carbon monoxide, carbon dioxide and moisture analysers connected to the control and alarm systems so that the main shut-off valve may close automatically if impurity levels exceed the pharmacopoeia specification, as the two oxygen analysers do for oxygen concentration. A sampling outlet allows oil, nitric oxide, nitrogen dioxide and sulfur dioxide to be tested, and the healthcare facility's qualified personnel decide from the risk management plan whether these are analysed continuously or periodically. The testing frequency of each contaminant comes from the site's risk analysis, and the responsible person checks that alarm set points and frequencies meet the requirements.

AIGA also notes that air intake contaminants such as oil, heavy hydrocarbons, acid gases and engine exhaust are not permanently monitored in continuous production, and that the facility's qualified personnel take responsibility for whether they could reach patients without continuous monitoring. Where oxygen 93 is compressed, it asks for carbon monoxide and carbon dioxide analysis downstream of that compressor to detect combustion by-products. See what happens to off-spec oxygen.

What other guidance says

Pharmacopoeia: the International Pharmacopoeia (13th edition, 2025) requires the Oxygen 93% production process to be validated against its limits and the oxygen content to be continuously monitored; for Oxygen 98%, made in two-stage plants, oxygen, carbon dioxide, carbon monoxide and water are monitored continuously and a risk assessment identifies any other impurities. It adds that healthcare facilities can use tests such as indicator tubes as spot checks.
Dryer warning: NHS England's HTM 02-01 (2026) notes that increasing or fluctuating carbon dioxide readings in PSA-generated oxygen can be an early indication of dryer failure or poor compressor maintenance, and HTM 02-01 Part B asks for the quality of gas from PSA plants to be tested at least quarterly.
Commissioning: the Global Fund commissioning guideline (28 August 2024) checks that output carbon monoxide and carbon dioxide meet International Pharmacopoeia limits where sensors are fitted.
Alarm checks: AIGA's safety checks include the carbon monoxide and carbon dioxide high level alarms and automatic shutdown functions, which could be tested with calibration gases for the detectors.

Ultra Controlo equipment

ULTRAOX SC plants measure oxygen with one or two zirconium oxide analysers, according to the datasheet. Ultra Controlo launched QuPHARM on 29 May 2026 as a wall-mounted purity analyser for on-site oxygen generation: according to its product page, it measures oxygen, carbon monoxide and carbon dioxide at the same time, with an optional moisture (H2O) transmitter, and has programmable alarm thresholds on the O2, CO and CO2 channels. See QuPHARM and how purity is measured in a PSA plant.