A look inside a desiccant dehumidifier.

 A look inside a desiccant dehumidifier.

A look inside a Meaco DD8L desiccant dehumidifier. (Which is actually a rebadged You Long YL-208A)

These dehumidifiers are much quieter than traditional compressor based ones. They work by rotating a drum of honeycombed desiccant material (zeolite) through an airflow from the area to be dehumidified, then through a heated section that drives the collected moisture out into a condensing panel.
I managed to fluff twice and suggest that these units are sensitive to being moved. They aren't. Traditional compressor dehumidifiers are sensitive to being moved during or just before use, since the refrigerant liquid can get into the compressor and stall it. These units can be dragged out the boot of a car and plugged straight in without a settling time.
The desiccant units are very lightweight since they do not contain much metal. Another advantage over the compressor versions is that these ones will operate efficiently down to near zero temperatures when there is virtually no moisture in the air anyway. Compressor units are very inefficient at low temperatures.
The reason for the air filter on the front of the unit is to prevent particulate from blocking the pores of the desiccant drum.
Although these units consume more power than an equivalent compressor unit with a low setting of typically 300W and a high setting of about 600W they don't use any more power overall since they bring the humidity down quickly and then turn off. The output is a stream of noticeably warm and very dry air.
These units are not to be confused with the absolutely useless desiccant dehumidifiers that are either a bag of silica gel or a chemical that absorbs moisture and then turns to slush in a plastic tub. The silica gel is OK for very small enclosed containers but not continuous room dehumidification.
Using a dehumidifier in a home prone to dampness like a coastal home or older style of building will solve many problems like mold and excess condensation on walls and windows. The dryer air is more comfortable and greatly reduces the need to heat the building excessively. Even at it's highest setting (about 600W) one of these units can be run continuously for a full day for considerably less than the cost of a cup of coffee from Starbucks. Most of these units have a laundry setting where wet washing can be hung indoors in the same room as the dehumidifier and it will dry it all quickly by removing the moisture from the air.
Although many of these units have quite complex electronic controls, I prefer the simpler version with just a high/low switch and a knob to set the desired humidity. Much simpler and potentially more reliable.dehumidifier reviews and buying guide best dehumidifier