How do high ambient temperatures affect a PSA oxygen plant and its compressors?

PSA oxygen plants are specified for a limited range of ambient temperatures, and the equipment generates heat that needs ventilation or cooling: WHO's 2020 interim specification (superseded in 2024) asked for the specified oxygen concentration continuously at 10 to 40 °C, and WHO's 2023 guidance asks for housing kept at 5 to 35 °C.

Does a PSA plant room need air conditioning?

PATH and CHAI (2021) say the equipment generates substantial heat and requires adequate air conditioning for cooling. HTM 02-01 (2026) asks for natural ventilation, or mechanical ventilation where natural ventilation is not practicable.

What temperature should a PSA plant room be kept at?

The documents differ: WHO's 2023 guidance gives 5 to 35 °C for PSA housing, and HTM 02-01 (2026) gives 10 to 40 °C for manifold rooms and plantrooms. The plant manufacturer's operating range is the one to check.

How does ambient temperature affect a PSA plant?

HTM 02-01, the NHS England guidance (2026), notes that PSA and medical air compressors draw in ambient air and, under maximum flow conditions, generate considerable heat. PATH and CHAI (2021) say that the equipment generates substantial amounts of heat and requires adequate air conditioning for cooling, and that the plant's operating environment should be kept with correct ventilation and cooling.

Temperature ranges in the guidance

The ranges differ, and apply to different things:

Document	Range	What it applies to
WHO interim technical specifications for PSA plants (8 June 2020)	10 to 40 °C, relative humidity 15 to 95%, elevation 0 to 1,000 m, minimum	Supplying the specified oxygen concentration continuously
PATH and CHAI brief on PSA and VSA plants (July 2021)	10 to 40 °C, relative humidity 15% to 95%, elevation 0 to at least 2,000 m	Supplying the specified oxygen concentration continuously
WHO, Foundations of medical oxygen systems (2023)	5 to 35 °C	Inside temperature of the dedicated housing that PSA plants require
NHS England, HTM 02-01 Part A (2026), paragraph 17.140	10 to 40 °C, and no more than 10 °C above ambient	Manifold rooms and plantrooms

HTM 02-01 asks for PSA compressors to comply with its medical air requirements, which ask for manufacturers to be consulted over the range of operating temperatures the supply system is designed for and note that, in extreme cases, refrigerator cooling may be required. For PSA plants it adds that refrigerant dryers may be included where the environmental conditions require them. The 2020 WHO interim specification asked for audible and visual alarms for high temperature.

Running a PSA plant in a hot climate

Design for the site. WHO (2023) asks for site-specific conditions such as elevation, temperature, humidity and dust to be addressed at the design phase, and Open Critical Care notes that the manufacturer needs the location to design the plant for altitude and the common temperature range.
Build the housing against heat. WHO (2023) says that where a roof with a metallic structure and corrugated sheets risks overheating the room, a more performant mechanical ventilation system will be needed. Open Critical Care suggests thermal mass or roof insulation to minimise heat transmission.
Ventilate the room and the compressor. HTM 02-01 asks for adequate natural ventilation, or mechanical ventilation where that is not practicable. Open Critical Care describes a second exhaust for the room, besides the one from the compressor, to keep good air circulation and a moderate temperature. AIGA 113/20 asks for the ventilation or air conditioning to keep room temperature and humidity within the manufacturer's operating range.
Record temperatures daily. Global Fund's daily maintenance checklist records the temperature of the PSA plant room or container and of the air compressor. Its 2025 guide to expected values asks operators to compare the room temperature with the manufacturer's operating range and to look for signs of overheating, such as frequent stops.
Stay within the limits. The USAID RISE operating procedure, written for hospitals in India, says not to operate the generator at pressures or temperatures above the maximum allowable limit in the datasheet or manual, and Global Fund sustainability guidance (2024) says that extreme heat and cold affecting PSA operation should be mitigated.

ULTRAOX plants

The ULTRAOX 2022 datasheet includes the ULTRASEC refrigeration dryer in its technical specifications. The ULTRASEC datasheet gives a maximum compressed air inlet temperature of 70 °C for the standard version and 100 °C for ULTRASEC-HT; these figures refer to the compressed air entering the dryer, as the datasheet labels them, not to the room. For the site conditions an ULTRAOX plant needs, see site requirements for an oxygen plant.