Medical air
What is a medical air treatment unit?
What does a medical air treatment unit do, and what stages does it have?
Short answer
A medical air treatment unit is the filtration and drying stage of a medical air plant: it takes air from the compressors and removes water, oil, particles and gaseous contaminants so that the air meets the pharmacopoeia limits for medical air before it enters the pipeline.
Medical air is made on site from the air around the plant. HTM 02-01, the NHS England guidance for medical gas pipeline systems, notes that medical air is produced from ambient intake air, so the cleaner the intake air, the higher the quality of the medical air produced. Air leaving the compressors still carries water and, with lubricated machines, oil. The treatment unit takes that compressed air to the quality of a medicine: the European Pharmacopoeia treats medical air as a medicine in monograph 1238.
Typical stages
HTM 02-01 (2026) describes a first separation stage that removes larger water and oil particles, followed by a dryer system that typically consists of a water filter/separator, an oil filter, two desiccant dryer columns, a dust filter, a carbon filter and a bacteria filter. While one desiccant column dries the air, the other is regenerated with dry air from the active column. The whole dryer assembly is duplicated so that supply continues if one side fails, and each assembly has its own dew-point sensor and test point after the bacteria filter, so it can be tested before going online and monitored continuously.
Two examples from the Ultra Controlo range
| Unit | Stages listed in the datasheet |
|---|---|
| ULTRAMED air treatment station | Coalescing filter for water, oil, aerosols and particles above 0.01 µm; activated carbon filter that reduces oil vapour and odours to 0.003 mg/m³; two adsorption columns that remove water vapour and reduce CO2, NO and SO2; catalyst filter that converts carbon monoxide into CO2; final dust filter |
| ULTRATECH breathing air purifier | 7 stages: micronic filter, sub-micronic filter, adsorption drying columns, CO oxidation column, CO2, NO and sulphur oxide reduction column, activated charcoal column, particle separator filter |
For medical air, Ultra Controlo advises adding a sterile air filter to the ULTRAMED stages. The ULTRAMED DS version monitors the dew point and stops column changeover when the target dew point is reached, which removes the need for purge air during that time. The ULTRATECH datasheet states that it produces breathable air from any type of compressor, and gives CO below 5 ppm and a nominal dew point of −46 °C in its air quality data.
How the result is checked
HTM 02-01 tests water vapour in two places: at the compressor plant to confirm dryer performance, and at terminal units to find contamination of the pipeline. Its acceptance limits for medical air include 5 ppm carbon monoxide, 500 ppm carbon dioxide, 1 ppm sulphur dioxide, 2 ppm nitrogen oxides, 67 vpm water vapour and 0.1 mg/m³ oil, and the plant raises an emergency alarm when dryness rises above −46 °C at atmospheric pressure.
More questions
Can a treatment unit make air from any compressor medical grade?
The ULTRATECH datasheet says it produces breathable air from any type of compressor. The delivered air still has to pass the pharmacopoeia tests at the plant and at terminal units.
Does a treatment unit need its own dew point monitoring?
Under HTM 02-01, the NHS England guidance, yes: each dryer assembly should have its own dew-point sensor and test point after the bacteria filter, for testing before it goes online and for continuous monitoring.
Sources
- ULTRAMED datasheet, p. 2 to 4
- ULTRATECH datasheet, p. 2 and 3
- NHS England, HTM 02-01 Medical gas pipeline systems, Part A (2026), paras 7.62 to 7.68, 7.89, 20.66 to 20.78
- EDQM, Ph. Eur. monograph 1238 Air, medicinal
Ultra Controlo figures come from its technical datasheets. Third-party facts were read at the source on the date shown.