# How many hours a day should a PSA plant run?

**How many hours a day can a PSA oxygen plant run, and what utilisation should be planned?**

A PSA oxygen plant can run 24 hours a day, 7 days a week, as the 2020 WHO interim specification for PSA plants (superseded in 2024) stated. For planning, Assist International (Open Critical Care) says it is reasonable to assume 80 to 90% of the plant's rated capacity as its actual working capacity.

## Built for continuous operation

The WHO Technical specifications for PSA oxygen plants (8 June 2020) said all medical PSA oxygen generator plants can produce medical-grade oxygen at scale 24 hours a day, 7 days a week, and WHO's COVID-19 guidance on oxygen sources (4 April 2020) said PSA plants are designed to function 24 hours a day. Both were issued as interim documents that stated they would expire two years after publication. WHO's Foundations of medical oxygen systems (2023) says the plant must be connected to a reliable and continuous source of energy for all intended hours of operation, and lists operators on site 24/7 and qualified technicians on call 24/7 for oxygen generator plants, depending on the facility or catchment area.

## What utilisation to plan for

- Rated capacity is a maximum. Assist International (Open Critical Care) notes that the manufacturer's rated capacity assumes the plant operates every minute of every hour, that this is unlikely in practice, and that it is reasonable to assume 80 to 90% of the rated capacity as the actual working capacity.
- Site conditions. The same answer notes that plants are rated at 1000 ft above sea level or lower and have to be derated at higher sites, and that the manufacturer needs the location, altitude and temperature range when the plant is ordered.
- Do not overdraw. The USAID RISE operating procedures (2022), written for hospitals in India, warn against drawing oxygen at a flow higher than the plant's capacity, which leads to a drop in purity and pressure and can cause failures of valves, sensors and gauges; see [why PSA purity drops when demand rises](https://library.ultracontrolo.com/answers/why-does-psa-purity-drop-when-demand-rises/).
- Check the balance every year. Global Fund sustainability guidance (2024) asks for oxygen production to be compared with consumption annually: an underused plant can serve an extended pipeline network or more cylinders for peripheral facilities, and an overused one may need secondary or tertiary sources.

## Stops for maintenance

Running hours drive the maintenance plan. WHO (2023) says the maintenance schedule may relate to the number of hours operated, giving the example of air and booster compressors that may need servicing after 2000 hours or 6 months of operation, and adds that some tasks should be done periodically even when the plant is not running continuously. Global Fund guidance asks for a back-up plan that covers plant breakdowns and shutdowns for scheduled service, with a defined maximum number of shutdown days. WHO also notes that configurations with more than one plant can alternate usage and scheduled maintenance, at the cost of higher maintenance resources; see what backup a hospital should keep.

## ULTRAOX plants

ULTRAOX plants start and stop oxygen production automatically in response to demand from the downstream distribution system, and switch compressors and start generators in cascade to keep a continuous supply. The ULTRAOX datasheet (2022) gives a design life of at least 150,000 hours, and the UltraCare programme aims to keep the equipment working 24/7, 365 days a year.

### Can a PSA plant run at full rated capacity all the time?

It is built for continuous operation, but Assist International (Open Critical Care) says it is reasonable to assume 80 to 90% of rated capacity as the actual working capacity, and the USAID RISE procedures (2022) warn that drawing more than the plant's capacity lowers purity and pressure.

### Does a PSA plant need staff at night?

WHO's Foundations of medical oxygen systems (2023) lists operators on site 24/7 and qualified technicians on call 24/7 for oxygen generator plants, depending on the facility or catchment area.

## Sources

- [WHO, Technical specifications for PSA oxygen plants, interim guidance (8 June 2020)](https://www.who.int/publications/i/item/WHO-2019-nCoV-PSA_Specifications-2020.1)
- [WHO, Oxygen sources and distribution for COVID-19 treatment centres, interim guidance (4 April 2020)](https://www.who.int/publications/i/item/oxygen-sources-and-distribution-for-covid-19-treatment-centres)
- [WHO, Foundations of medical oxygen systems (17 February 2023)](https://iris.who.int/server/api/core/bitstreams/4ad6f5fd-089e-4142-8439-b64e98d816d8/content)
- [Open Critical Care, Oxygen FAQ: How do you calculate the conversion between a PSA plant's rate of oxygen production and cylinder volumes that can be filled? (FAQ by Assist International)](https://opencriticalcare.org/faq/how-do-you-calculate-the-conversion-between-a-psa-plants-rate-of-oxygen-production-and-cylinder-volumes-that-can-be-filled/)
- [USAID RISE, Standard Operating Procedures: PSA Plant Operations and Preventive Maintenance (March 2022)](https://media.path.org/documents/SOP_on_PSA_Plant_USAID_RISE_04032022_F7fUBr6.pdf)
- [Global Fund / Build Health International, Overview: Sustainability Guidance for PSA Oxygen Plants (22 August 2024)](https://resources.theglobalfund.org/media/bwrp43cm/cr_c19rm-psa-oxygen-plant-sustainability_overview_en.pdf)
- [ULTRAOX datasheet 2022, p. 4 and p. 6](https://www.ultracontrolo.com/ultraox)
- [ULTRAOX SC datasheet, p. 2](https://www.ultracontrolo.com/products/ultraox)
- [ULTRAOX ST datasheet, p. 2](https://www.ultracontrolo.com/products/ultraox-st)
- [WHO, Technical specifications for health facility based medical oxygen systems (31 December 2024), note on the oxygen generator plant specification (supersedes the 2020 interim PSA specifications)](https://iris.who.int/server/api/core/bitstreams/ff437601-add3-44c8-8149-b85f0cdb2b52/content)

Reviewed: 2026-10-22. Ultra Controlo engineering. https://library.ultracontrolo.com/answers/how-many-hours-a-day-should-a-psa-plant-run/