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Is the absolute dehumidifying capacity affected by ambient temperature and humidity?

Rosahl membranes remove moisture from an enclosure. The manufacturer publishes dehumidifying capacity at 30° C and 60% RH as an indication of performance. This is not the absolute dehumidifying capacity of the membrane

Exactly how much moisture they remove depends on the temperature and absolute humidity (g/m³) in the enclosure. The capacity changes as the absolute moisture in a cabinet changes. This information is reflected in the drying curves published by the manufacturer

Drying curves for Rosahl dehimidifying membranes

Absolute dehumidifying capacity

As an example, we consider a size 10 membrane M-10J1R. The published capacity of this device is 29g/day. This is based on ambient conditions of 30° C and 60% RH. Under these conditions, the absolute humidity is 19.1g/m3 (from tables)

The M-10J1R membrane capacity of 29g/day changes as temperature and humidity change as follows:

At 30℃・40RH

Absolute moisture is 12.7g/m3 → 29*(12.7/19.1) =19.3g/day membrane capacity

At 30℃・90% RH

Absolute moisture is 28.6g/m3 → 29*(28.6/19.1) =43.4g/day membrane capacity

At 20℃・60RH

Absolute moisture is 10.5g/m3 → 29*(10.5/19.1) =15.9g/day membrane capacity

At 40℃・60% RH

Absolute moisture is 33.2g/m3 → 29*(33.2/19.1) =50.4g/day membrane capacity



At 30℃, when RH is higher than 60% the membrane will remove more moisture, and when RH is less than 60% it removes less moisture than the published capacity

At 60% RH, when temperature is lowerer than 30° C the membrane removes less moisture, and when temperature is above 30° C it removes more moisture than the published capacity


ModelDehumidifying capacity* 
PD4/PD542 mg/day
PD2/PD3/RD3/RD484 mg/day
M-2J1R2g /day
M-3M1R2.9g /day
M-3J1R/MDL-34g /day
8g /day
16g /day
29g /day
* Initial dehumidifying capacity of a new membrane at 30C and 60% RH