# What filters does a medical air system need?

**Which filters does a medical air system need, from the compressor to the pipeline?**

A medical air system typically has an inlet filter on each compressor, a water separator, a water filter and an oil filter, desiccant dryer columns, a dust filter, a carbon filter and a bacteria filter before the pipeline, as described in HTM 02-01 (2026).

Medical air is filtered in stages. HTM 02-01 (2026), the NHS England guidance for medical gas pipelines, describes this sequence for a typical medical air plant:

1. Air-inlet filter immediately upstream of each compressor, a dry medium or grade CA paper element filter complying with BS ISO 5011.
2. Inline cyclone water separator between each compressor and the receivers, with a timed solenoid drain.
3. Water filter/separator and oil filter, fitted as individual components.
4. Two desiccant dryer columns: one dries the air while the other is regenerated with dry air from the active column.
5. Dust filter.
6. Carbon filter.
7. Bacteria filter, followed by the dew point sensor and test point of the dryer assembly.

The whole dryer assembly is duplicated by a second one to ensure continuity of supply. HTM 02-01 notes that a differential pressure gauge signals critical failure rather than servicing needs, so it does not replace regular inspection.

## How Ultra Controlo builds it

The ULTRAMED treatment unit combines these stages: a high efficiency coalescing filter for water, oil, aerosols and particles above 0.01 µm; an activated carbon filter that reduces oil vapour and odours down to 0.003 mg/m³; two adsorption columns with desiccant for water vapour; a catalyst filter that converts carbon monoxide into carbon dioxide; and a final dust filter for particles carried over from the adsorption material. For medical air, Ultra Controlo advises adding a sterile air filter.

On ULTRAAR ME, each pressure regulator carries a sterile air filter with 99.999998% efficiency at 0.01 μm. ULTRAK activated carbon towers, which remove oil vapour by adsorption, need a coalescing filter upstream, and the datasheet recommends a 1 μm dust filter downstream.

### Does medical air need a sterile filter?

HTM 02-01 includes a bacteria filter in the typical dryer system, and Ultra Controlo advises adding a sterile air filter to the ULTRAMED treatment unit for medical air.

### Do oil-free compressors need fewer filters?

HTM 02-01 says oil-free compressors reduce filtration requirements and minimise the risk of oil contamination.

## Sources

- [NHS England, HTM 02-01 Medical gas pipeline systems (2026), Part A, 7.29, 7.34, 7.46 and 7.64 to 7.72](https://www.england.nhs.uk/wp-content/uploads/2016/05/health-technical-memorandum-02-01-medical-gas-pipeline-systems-part-a-design-installation-validation-verification-aug-2026.pdf)
- [ULTRAMED datasheet, p. 3](https://www.ultracontrolo.com/products/ultramed)
- [ULTRAAR ME datasheet, p. 3](https://www.ultracontrolo.com/products/ultraar-me)
- [ULTRAK datasheet, p. 2](https://www.ultracontrolo.com/products/ultrak)

Reviewed: 2026-10-22. Ultra Controlo engineering. https://library.ultracontrolo.com/answers/what-filters-does-medical-air-need/