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

What is Rosahl?

Rosahl is a unique electric micro-dehumidifier for very small spaces and enclosure where maintenance-free drying is an important factor. It uses a solid polymer membrane (SPE) installed in a flat panel, making it suitable for use in a wide range of enclosures from under two litres up to 4m³ (140 cu ft) in volume.

The name Rosahl comes from a Japanese phrase meaning “removing dew”, and it was developed by the Mitsubishi Electric Corporation in Japan in response to a demand for compact and maintenance free air drying solutions to protect sensitive equipment from moisture damage. It has since found its way into uses for protecting museum display cabinets, telecommunications equipment, manufacturing processes and electrical cabinets.

Rosahl dehumidifiers work using electrolysis when connected to a 3V DC low power source. As the membrane has no moving parts, it is silent, vibration free, and has a very low average energy footprint. The process does not produce liquid water, making it maintenance free and giving the membrane a long operating life.

Designed for industrial and commercial applications, Rosahl membranes offer a long-term solution to humidity control for enclosures.  It is particularly useful for equipment in remote locations, or where a conventional dehumidifier would be difficult to maintain or service. It will operate over a temperature range of -10 to +50°C

Rosahl is the World’s smallest electric dehumidifier

A range of models is available, and selection is based on the application, and the size of the enclosure. The entry-level membranes are designed for enclosures under two litres and are 75% smaller than an AA battery, making them ideal for CCTV and IP camera applications.

Using Rosahl membranes

Rosahl membranes are used to reduce the humidity inside sealed enclosures up to 4m³ (140 ft³). They are normally mounted over a cut-out in the side of the enclosure to be dehumidified, and through which they expel the moisture. When a low voltage DC supply is connected to the membrane, it splits (disociates) the moisture into hydrogen and oxygen ions. The hydrogen ions are expelled by the membrane to the outside. See how Rosahl works here

By changing the direction the membrane is facing, it can be used as a humidifier provided the ambient humidity is sufficient. A pair of membranes under can also be used to balance humidity when fitted with the appropriate controls.

Rosahl flat panel dehumidifier
Rosahl dehumidifier membrane compared to AA battery

Benefits of Rosahl

ROSAHL dehumidifiers are:

  • Silent and vibration free so they can be used virtually anywhere
  • Maintenance free to reduce lifetime operating costs
  • Drain-less, so no water removal or cleaning is required
  • Ultra-compact, devices will fit almost any enclosure
  • Environmentally friendly design with low power consumption
  • Long operating life
  • Available also for use as humidifiers or for balancing precious environments


Factory Quality Standards

ISO 9001 Certified

ISO 14001 Certified

Why use Rosahl?

Rosahl products are extremely versatile and used in a wide variety of applications to humidify or dehumidify enclosed spaces.  Applications range from storage areas for sensitive equipment through to challenging external environments such as traffic control cabinets and many other uses.  Rosahl is a low energy moisture extraction system and has a low capacity relative larger conventional  (condensing) dehumidifiers.

They are best used in enclosed areas of up to 4m³ (140 ft³).  Unlike condensing humidifiers they are small, have no moving parts and are silent: unlike silica gel, they do not need to be regularly recharged or replaced.

Since ROSAHL products use very little energy compared to other types of humidification, they can be left to run 24 hours a day, 365 days a year continuously extracting moisture from an enclosed area without incurring major energy costs. They are maintenance free and may be left for years without concern.

Selecting Rosahl

Using Rosahl membranes to dehumidify an enclosure or cabinet is a simple process and starts with selection of the module type.  Membranes are generally supplied as components to enable the installer to mount them as needed. Suitable power supplies are also available.


Go here for the product range


Go here for selection information

Typical Rosahl Applications

With the smallest version the size of a thumbnail, there are few locations where ROSAHL dehumidifiers cannot be used.  They are suitable for a wide range of applications and can be used almost anywhere there is an electrical supply available, including protecting CCTV cameras.  Other popular applications include protecting:

  • Traffic control and display cabinets
  • Outdoor multimedia screens and displays
  • Mobile telecommunications outstations
  • Precision equipment storage cabinets
  • Museum displays and exhibition cabinets
  • Protecting sensitive opto and electronic devices
  • Storage of hygroscopic materials
  • Semiconductor manufacturing
  • Infrared spectrographs

External LED lighting

Who uses Rosahl?

Some customers purchasing ROSAHL products include:

  • Sanyo (outdoor monitors UK),
  • Smiths Industries (baggage security detectors UK)
  • Stopworm (Musuem cabinets France).
  • Engtek (External monitors, Singapore)
  • Bruker, Optics (Lasers, Germany)
  • Jenoptik (Lasers, Germany)
  • Guyot (Musuem cabinets France)
  • White Water (Laboratory cabinets, USA)
  • Preservatech (Museum cabinets-Canada)
  • Vivotek (CCTV cameras-Taiwan)
photo of Rosahl installation

Expensive damage due to humidity can easily be avoided

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