At what pressure is medical air supplied to wards and to surgical tools?

In NHS England guidance, medical air for ventilators and other respiratory uses is supplied at 400 kPa and surgical air for air-powered tools at 700 kPa or more; the Portuguese ACSS specification uses 450 kPa ±100 on secondary networks and 8 bar +2/−1 for surgical instruments.

Why is medical air pressure set between oxygen and nitrous oxide?

ACSS recommends oxygen above medical air and medical air above nitrous oxide in secondary networks, ideally 0.3 bar apart, to prevent one gas flowing back into another.

Do surgical tools need a separate compressor plant?

Not necessarily. HTM 02-01 recommends a single combined system for medical and surgical air to reduce maintenance and overall energy consumption.

What pressure is medical air supplied at?

Pipeline pressure depends on what the air has to drive. HTM 02-01 (2026), the NHS England guidance for medical gas pipeline systems, says air should be provided at two different pressures but to the same British Pharmacopoeia standard: 400 kPa for medical air to drive ventilators and other respiratory applications, and 700 kPa or higher for surgical air to drive surgical tools.

Medical air at 400 kPa

Medical air at 400 kPa feeds ventilators and is increasingly used for CPAP, BiPAP and non-invasive ventilation in critical care. HTM 02-01 notes that pneumatically powered ventilators can use up to 80 L/min of free air continuously, and that other equipment on the same supply, such as anaesthetic gas mixers, humidifiers and nebulisers, should not exceed 10 L/min.

Surgical air at 700 kPa

HTM 02-01 notes that air-powered surgical tools need between 600 and 700 kPa, with flows from 200 to 350 L/min. It asks for a minimum of 700 kPa at the front of each terminal unit when tested at 350 L/min, and a static pressure at the terminal unit of no more than 900 kPa. Where surgical air is extended to a dental department, a duplex pressure-reducing station brings it down to 600 kPa.

Portugal: ACSS ET 03/2006

Network	Pressure (ACSS ET 03/2006 v.2024)
Medical air, primary network	900 kPa ±100
Medical air, secondary networks	450 kPa ±100
Medical air, specific cases	800 kPa +200/−100
Surgical instruments (per ISO 7396-1)	8 bar +2/−1

ACSS also recommends that, in the secondary networks, oxygen pressure is above medical air pressure and medical air pressure is above nitrous oxide pressure, ideally 0.3 bar apart, to prevent backflow of one gas into another.

Plant pressure and pipeline pressure

The plant produces air above pipeline pressure and reduces it before the network: in HTM 02-01 the treated air passes through a pressure-reducing station that sets the pressure for each use. As an example from the Ultra Controlo range, the ULTRAAR SCA datasheet gives a normal operating pressure of 7.5 to 7.9 bar and a maximum of 10 bar, with a duplex pressure-reducing kit and sterilisation filter that hold the network at the set pressure.