science 101

warm air holds more moisture than cold therefore most dehumidifiers work by drawing air through a condensator which is set to run cooler than the surrounding air,

problems caused by condensers.. things like wood furniture would normally stabilize its self to the ambient air conditions a sudden reduction in moisture will cause rapid shrinkage and cracking the same would apply to wall plaster

healthwise reducing the moisture too much is likely to cause dry throat ts higher than normal thirst, increaced perspiration

wizard

I would agree with engineer number 1 plug it in for a few hours to just take the dampness out of the air without drying everything out too much. Do you own a property on the Algarve? In winter they can be a help to stop mold forming on walls etc, as wizard says warm air holds more moisture, so if you are using a lot of heating appliances during the winter/rainy months without adequate ventilation they can help tremendously, but dont over-do it. Cheers Jayjan

Thanks wizard and jayjan for your helpful replies to my query
I own a place in V da Telha near A|ljezur and because I can only visit infrequently there is a definate mouldy smell
I will be there next week so will open out all doors/windows as well as using the dehumidifier sparingly!