+44 203 286 8189 steve.jones@westside-int.com

Rosahl low temperature dehumidifier operates at sub-zero temperatures

The Rosahl membrane dehumidifier operates below freezing and effectively throughout its operating temperature range of -20C to +50C (-4 to 122F). Operating below freezing is unusual for an electrical dehumidifier, but Rosahl membrane dehumidifiers are unaffected by the freezing point of water as they operate at the molecular level.


No liquid water

A membrane dehumidifier operates below freezing at a molecular level meaning that no liquid water is involved. This also means no cleaning or other regular maintenance is required and ensures the overall operating costs are minimised.

Rosahl is a solid state device using a solid polymer electrolyte (SPE) which ensures it is reliable in operation, inexpensive to run, and has a long service life. As the micro-dehumidifier contains no moving parts, there is no noise or vibration allowing it to be used almost anywhere, so the installation is simplified


Ionic pump

Rosahl works like an ionic pump and is often referred to as an ionic membrane dehumidifier.  When a low voltage (3V D.C.) is applied to the membrane, the moisture on the inside of the enclosure breaks down (dissociates) into hydrogen ions (H+) and oxygen: the hydrogen ions migrate through membrane to be discharged on the outside side where they react with oxygen in the air, resulting in water molecules (gas), being discharged. This gives Rosahl a number of advantages over other types of dehumidifiers in freezing conditions.

Wide range of uses

Rosahl is suitable for use in a wide range of enclosed industrial and commercial cabinets up to 4 cubic metres, and the smallest version-suitable for a space up to two litres- is 75% smaller than a regular AA battery.  Popular applications include

  • Traffic control and display cabinets
  • Mobile telecommunications outstations
  • Precision equipment storage cabinets
  • Museum displays and exhibition cabinets
  • Protecting sensitive opto and electronic devices
  • Storage of hygroscopic materials
  • FT-IR spectrographs
  • LED and lighting application

Advantages of Rosahl micro-dehumidifiers


Silent & vibration free

Rosahl dehumidifiers have no moving parts so there is no noise or vibration when operating.


Maintenance Free

Rosahl requires no regular maintenance, reducing total cost of ownership (TCO)

Long Operating Life

Rosahl uses a solid-state ionic membrane giving it a long service life and low operating costs

Low Energy Footprint

Rosahl membranes operate at 3V d.c. and use a very low average operating current to save energy


Ultra Compact

75% smaller than an AA battery, Rosahl can be used in enclosures from 250ml

Operates Below Freezing

Tested to -20°C, Rosahl may be used for internal and external applications

No moving parts

Rosahl dehumidifiers have no moving parts so there is no noise or vibration when operating and nothing to wear our or service

Solid-state membrane

Solid-state polymer electrolyte (SPE) provides reliable operation with low average power consumption and a long service life

No liquid water

The process works at a molecular level and no liquid water is involved, so no cleaning or drainage are needed