# Dew point monitor

Under HTM 02-01 (2026), the NHS England guidance, each medical air dryer assembly should have its own dew-point sensor and test point after the bacteria filter, for continuous monitoring of the air; Portugal’s ACSS ET 08/2010 (V.2025) asks for a dew point monitor with an alarm on each technical air drying line.

In HTM 02-01 (2026), the dryer control unit should contain hygrometers set to −46 °C atmospheric dew point and an automatic changeover to the standby dryer if the duty unit fails by dryness or pressure, and dryness above −46 °C at atmospheric pressure is one of the plant emergency conditions the plant monitoring system should detect. The sensor sits after the bacteria filter of each dryer assembly, so that the assembly can be tested before it is brought online.

ACSS ET 08/2010 (V.2025) asks for the monitor on each drying line to have a digital display, to be connected to the plant alarm system and to trigger a visual and audible alarm if the dew point exceeds the preset safety value. See also [pressure dew point](https://library.ultracontrolo.com/glossary/pressure-dew-point/).

ULTRAAR ME has two integrated ULTRAGEST systems that monitor and control the dew point of the medical air supplied to the network continuously. ULTRAMED DS uses electronic dew point monitoring to stop column changeover when the ideal dew point is reached, and the ULTRAMED datasheet lists a low dew point indicator alarm and continuous outlet dew point monitoring through a digital dew point indicator, which is not included. The ULTRASEC refrigeration dryer has a digital dew point indicator.

## Sources

- [HTM 02-01 (2026) Part A, paragraphs 7.68, 7.87 and 7.89 (NHS England)](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)
- [ACSS ET 08/2010 V.2025, Especificações técnicas para ar comprimido técnico em edifícios hospitalares, section 4.2.6.4](https://www.acss.min-saude.pt/wp-content/uploads/2016/10/ET-08_2010_V.2025_VF.pdf)
- [ULTRAAR ME datasheet, p. 2](https://www.ultracontrolo.com/products/ultraar-me)
- [ULTRAMED datasheet, p. 2 and p. 3](https://www.ultracontrolo.com/products/ultramed)
- [ULTRAOX Technical Data Sheet 2022, p. 12 (ULTRASEC)](https://www.ultracontrolo.com/products/ultraox)

Reviewed: 2026-10-22. Ultra Controlo engineering. https://library.ultracontrolo.com/glossary/dew-point-monitor/