How long must the reserve last?

AIGA 113/20 says the reserve should supply oxygen long enough for one oxygen 93 source to be restarted after an electrical power failure or a technical problem.

Does a PSA plant restart on its own?

NHS England's HTM 02-01 (2026) asks that the operating system be capable of restarting automatically after power is reinstated, with compressors restarting in sequence.

What happens to a PSA plant during a power cut?

Q: What happens to oxygen supply when a PSA plant loses power, and how is it restarted?

A PSA plant shuts down when it loses power, since oxygen 93 units depend on electricity (AIGA 113/20); the pipeline then relies on emergency power or a reserve source independent of electricity, and NHS England's HTM 02-01 (2026) asks that the plant be able to restart automatically, compressors in sequence, once power returns.

What happens to oxygen supply when a PSA plant loses power, and how is it restarted?

When the power fails

AIGA 113/20, adopted from EIGA Doc 195, says that when an oxygen 93 generator shuts down, planned or unplanned, for example through a power failure, there is usually a built-in fail-safe system of shutdown events, and a number of actions happen automatically to leave the supply system in a safe standby condition.

Because oxygen 93 units depend on the electrical supply, AIGA asks for either an emergency electrical supply with a backup generator or a second electrical supply that the failure would not affect, and for at least one of the three supply sources to be independent of electricity: a liquid storage container, high-pressure cylinders or bundles. It lists electrical power failure as a failure mode common to the primary and secondary concentrator units, recommends connecting the oxygen 93 system to the hospital's emergency supply, with a check that this supply can run the system at design capacity, and asks for a reserve sized to supply oxygen until one oxygen 93 source can be restarted.

NHS England guidance, HTM 02-01 (2026), says all components of a PSA supply system should be connected to the essential electrical supply. PATH and CHAI (July 2021) state that a backup supply, such as cylinders, is required to maintain oxygen flow during a power outage or mechanical failure, and the 2020 WHO interim specification for PSA plants (superseded by WHO's technical specifications of 31 December 2024) listed a power failure alarm among the required alarms.

Switching to backup power

WHO, Foundations of medical oxygen systems (2023), says the primary and secondary power supplies must be connected to the plant's power cabinet through a transfer switch system; an automatic transfer switch is ideal because it reduces the transfer time delay, while a manual one requires less maintenance. The Global Fund (4 March 2025) notes that large PSA plants can have high compressor in-rush currents, for which the generator and switchgear must be sized, and its commissioning guideline (28 August 2024) checks that backup power meets the plant's start-up and running loads and has the same phase rotation as the primary supply.

Restarting

HTM 02-01 (2026) asks that the operating system be capable of restarting automatically after the power supply is reinstated, that compressors restart in sequence to avoid overloading the essential power supply, and that two or more compressors do not start simultaneously when power is applied.

AIGA 113/20 adds procedural checks: before any restart after a planned or unplanned shutdown, all process parameters, including online analysis, are verified within the specified limits, and once the system has started, conditions are checked before it runs unattended and re-checked after several hours. It also asks for precautions, such as lock-out and warning signs, so that equipment cannot restart automatically without the knowledge of people working nearby. For an oxygen 93 source on standby, the oxygen buffer is sized to supply the nominal flow throughout its start-up.

ULTRAOX

The ULTRAOX datasheet (2022) asks the customer to provide the three-phase electrical supply and states that the plant can be connected to a diesel-electric generator; its electrical control panel provides all alarms on an interface for remote signalling.