How often should a PSA plant's oxygen analyser be checked?

Check frequencies in the guidance

When the readings disagree

The USAID RISE procedure lists a faulty sensor, and a faulty PLC reading that must be calibrated as the manufacturer recommends, among the points to check when purity is low. HTM 02-01 asks for connections for calibration cylinders at the plant, alongside its duplex monitoring system, and PATH and CHAI (2021) include calibrating pressure and oxygen sensors in the preventive maintenance a buyer can contract to the manufacturer. The 2020 WHO interim specification asked for the plant's oxygen concentration monitor to have ±1% accuracy.

As reference points, Global Fund's 2025 guide to expected values treats above 90% as medical grade and says that a reading below 85% should lead to an investigation, while HTM 02-01 isolates a PSA plant from the pipeline below 94%. Open Critical Care says periodic checks need oxygen analysers and suggests asking the manufacturer or authorised distributor for the specific analysers needed for maintenance, and WHO (2023) lists an oxygen analyser in the maintenance toolkit that operators should have.

Records

Global Fund's checklist asks the technician who completes it to initial the form, and asks for a separate set of records for each system in a duplex or triplex plant.

Ultra Controlo analysers

Ultra Controlo supplies a portable oxygen purity analyser for on-site checks of oxygen concentration in pipelines and cylinders. On ULTRAOX SC plants, purity is measured by one or two oxygen analysers with a zirconium oxide probe, and the QuPHARM wall-mounted analyser, launched in May 2026, has programmable alarm thresholds on its oxygen, carbon monoxide and carbon dioxide channels.