Litres per minute (L/min, LPM)

The guidance, on oxygen sources and distribution for COVID-19 treatment centres, sizes PSA plants by output capacity in m³/h of oxygen gas. Its worked example is 75 severe COVID-19 patients at 10 L/min: 75 x 10 x 60 = 45,000 L/h, or 45 m³/h.

PATH and CHAI (July 2021) give the nominal flow of a conventional PSA plant as 8 to 2,500 litres per minute (LPM), or 0.5 to 150 Nm³/h, at 50 psi, and the typical maximum output of an oxygen concentrator as 3 to 12 LPM. HTM 02-01 (2026), the NHS England guidance, sets surgical air at a minimum of 700 kPa at the terminal unit at a flow of 350 L/min or 100 L/min. Plant capacities given in Nm³/h refer to reference conditions; see normal cubic metre.

The ULTRAOX SC model table gives each model in both units, for example 5.3 l/min, or 0.318 m³/h, per unit for model 3.