# What performance guarantees should a PSA plant contract include?

**What performance guarantees should a PSA oxygen plant contract include for flow, purity, pressure, energy and design life?**

WHO's technical specifications for oxygen generator plants (December 2024) ask for a specified output flow, oxygen of at least 93 ±3%, an output pressure of 500 to 800 kPa unless aligned to the pipeline design, a manufacturer-guaranteed lifespan of at least 10 years, spare parts for 10 years, and a 72-hour run before commissioning.

The December 2024 specifications supersede WHO's 2020 interim specifications for PSA plants and are generic minimum requirements to be adapted to each project. UNDP's REQ-OXY-001 (effective 1 January 2025) adds its own evidence requirements.

## What to fix in the contract

| Item | WHO (December 2024) | Other documents |
|---|---|---|
| Flow | Required output specified with its units (Nm³/h, LPM or SCFH); air feed sized at a minimum of 5x the expected output plus an allowance for elevation | UNDP (2025): specifications must address flow rate, purity, pressure, energy efficiency and compatibility with existing systems |
| Purity | At least 93 ±3% V/V, measured with ±1% accuracy; automatic shut-off on non-conformance (factory set for oxygen below 90%) with manual override | Global Fund (3 April 2024), as an example: a 20 Nm³/h plant set to 93 ± 3% could give 20 Nm³/h, and the same equipment set to 95 ± 1% would give 18 Nm³/h |
| Pressure | Output 500 to 800 kPa, or aligned with the applicable standard and system design if connected to a pipeline; alarms below 5 bar or above 8 bar |  |
| Environment | Continuous operation within specification at ambient temperatures of at least 5 to 40 °C with 15 to 95% relative humidity; elevation specified; vendor to propose measures outside this range |  |
| Energy | Vendor to indicate the estimated total power consumption, back-up power supply size and peak current during start-up |  |
| Life and parts | Lifespan of at least 10 years guaranteed by the manufacturer, with a lifespan guarantee certificate; spare parts available for at least 10 years from acceptance; post-warranty software and firmware upgrade support from the PLC manufacturer | UNDP (2025): a 10-year lifespan guarantee and a 24-month warranty from the manufacturer |
| Warranty | At least 1 year from commissioning, with 24 hours a day, 7 days a week remote support for manufacturer defects | See [what warranty comes with an oxygen plant](id:what-warranty-comes-with-an-oxygen-plant) |

## How the performance is proven

- Before shipment: WHO (2024) asks for a pre-shipment inspection report with all certificates of analysis of the product output, technical tests and calibration, and for technical tests for safety and performance from an accredited laboratory or third party, where applicable. UNDP asks for official performance test reports for key parameters including purity, flow and pressure, all pages in English, from test laboratories accredited by an ILAC member or from an EU notified body.
- On site: WHO asks for tests documented under the manufacturer's protocols and cross-checked with the pre-shipment inspection, verification of the automatic switch-over to the secondary or reserve supply, and at least 72 hours of continuous operation to test the entire system before commissioning, checking all analysers and alarms, including power failure. UNDP requires pre-shipment inspection, performance tests with at least three days of continuous operation, alarm tests and commissioning reports, makes the supplier responsible for acceptance testing of purity, flow, pressure, functionality and alarms, and encourages independent verification by certified third-party organisations, where available.
- After installation: a PATH analysis of PSA plant failures (November 2023) recommends an independent inspection after installation by a third party not involved in procurement.

## How WHO (2024) defines the warranty

WHO (2024) uses warranty to mean a guarantee of the product or components from commissioning covering manufacture-related issues or defects; it does not cover after-sales service such as operations, preventive maintenance or repairs from operational wear and tear. Terms and conditions can be negotiated, and expectations of any service must be clearly indicated, with explicit details of the responsibilities of the parties; see what a maintenance contract covers.

## Ultra Controlo

The ULTRAOX SC datasheet states that the equipment is parameterised and tested in the factory and will be ready to start on site. How ULTRAOX plants compare with the WHO specifications is set out in does ULTRAOX meet the WHO PSA specifications.

### How long should a PSA plant be guaranteed to last?

WHO's 2024 specifications ask for a lifespan of at least 10 years guaranteed by the manufacturer, with spare parts available for at least 10 years from acceptance.

### How long should the plant run before commissioning?

WHO (2024) asks for at least 72 hours of continuous operation to test the whole system, and UNDP (2025) for performance tests of at least three days of continuous operation.

## Sources

- [WHO, Technical specifications for health facility based medical oxygen systems (December 2024), oxygen generator plants, lines 18 to 52](https://iris.who.int/server/api/core/bitstreams/ff437601-add3-44c8-8149-b85f0cdb2b52/content)
- [UNDP, REQ-OXY-001 v01, Technical and regulatory requirements for oxygen plants (effective 1 January 2025), sections 5.2.3, 6.1, 6.2 and 7.4](https://healthimplementation.undp.org/wp-content/uploads/2025/01/REQ-OXY-001-v01-UNDP-TECHNICAL-REGULATORY-REQUIREMENTS-FOR-OXYGEN-PLANTS.pdf)
- [Global Fund / Build Health International, Briefing Note: PSA Plant Oxygen Purity (3 April 2024)](https://resources.theglobalfund.org/media/lenpqaoa/cr_c19rm-psa-oxygen-purity_technical-briefing-note_en.pdf)
- [PATH, Pressure swing adsorption plants: common issues and solutions to prevent future disrepair (November 2023)](https://media.path.org/documents/Root_cause_analysis_report_external_clean.pdf)
- [ULTRAOX SC datasheet, p. 3](https://www.ultracontrolo.com/products/ultraox)

Reviewed: 2026-10-23. Ultra Controlo engineering. https://library.ultracontrolo.com/answers/what-performance-guarantees-should-a-psa-contract-include/