According to the 2002 European Pharmacopoeia, published by the European Department for the Quality of Medicines in Strasbourg, the recommended maximum allowable moisture concentration is 67 parts per million by volume (-46 °C dew point).
The UK’s Health Technical Memorandum (HTM) recommends that “all medical gas supplies should be continuously monitored for dew point or moisture content” and recommends an electronic dew-point meter in preference to water content measurements.
Online measurements of water dew point
The Easidew Online hygrometer from Michell Instruments continuously measures and displays both dew point and water content. It is compact, easy to install and has a measurement accuracy of ±2 °C dew point. With a wide measurement range from –100 to +20 °C dew point the recommended -46 °C dew point level for medical gases falls well within its capabilities.
Portable hygrometers for fast spot-checks
Michell Instruments’ MDM300 high-speed portable dew-point hygrometer is used for rapid spot-checks of dew point and moisture content in medical gases. As well as the ability to quickly dry down between measurements, the MDM300 is compact, lightweight and has a long battery life to maximise its efficiency.