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Rosahl membrane is a very low power electric dehumidifier designed for long-term humidity control in steady state cabinets. In this, steady state means without excessive leakage areas allowing moisture to ingress.

Membrane dehumidifiers are available in a range of sizes to suit enclosures from under one litre to over 4 m³ (140 ft³) water vapour extraction rates ranging from 84mg/day up to 29 g (grams) for the larger sizes.

Low power consumption

Power consumption of the membranes varies considerably depending on the relative humidity present; the higher the humidity, the higher the power consumption. As the moisture inside the enclosure is removed, the electrical power used by the dehumidifier also reduces until it reaches a stable level. Where the dehumidifier membrane is controlled by a hygrometer the power to the dehumidifier can be removed until it is required again. This is particularly important as some natural substances require a level of humidity to retain their composition or structure.

To avoid deterioration and damage of products or to achieve proper process conditions, environment and the indoor climate must often be within certain temperature and humidity limits. Low relative humidity may dry up products and high relative humidity may increase the water activity and growing mould and bacteria in the production or process lines. For more information, go to the Engineering Toolbox.

Ambient humidity is high variable and affected by temperature. When publishing power consumption data, the figures are the annual average consumptions based on the Japanese climate, where the outdoor humidity averages between 60% and 80%, but with day-time highs of 95%.


Table of membrane dehumidifier power consumption

 Model Dehumidifying capacity Average power consumption Maximum enclosure volume
Grams/day Watts
PD & RD Series 0.084 .080 2 litres
M-2J1R 2 1 0.25
M-3M1R 2.9 1.8 0.35
M-3J1R, MDL-3 4 2 0.5
M-5J1R, MDL-5 8 3 1
M-7J1R, MDL-7 16 4 2
M-10J1R 29 8 4


very low power electric dehumidifier

Lower power consumption

The ROSAHL membrane dehumidifiers utilises porous electrodes on each side of a hydrogen-ion conductive electrolyte film for transferring moisture from the anode to the cathode and dehumidifying it. The process is called electrolysis.

In terms of energy consumption, it uses approximately 2% of a heater system and 20% a Peltier system: for example, Rosahl is capable of dehumidifying 2m3 (70cu ft.) enclosure using 5W of power, whereas the heating (compressor) and Peltier systems require 250W and 50W respectively.

Long maintenancePrevent condensation damage

ROSAHL has the added advantage of no moving mechanical components and reacts only with water vapour to prevent condensation damage: there is no noise or vibration and it requires no drainage as the process does not involve liquid water.  In addition to preventing unsafe conditions (corrosion etc.) and extending the service life of the control panel and its components, the utilisation of ROSAHL dehumidifiers reduces the energy consumption and negative environmental impact of the unit.  The ionic membrane used in the process also has a long operating life.

By preventing moisture in storage areas ROSAHL can also be used in a wide variety of applications including CCTV and IP cameras, foodstuff and pharmaceutical storage, museum exhibits, electro-optics and medical equipment.

Advantages of Rosahl dehumidifiers