According to Air-N-Water, dehumidifiers remove moisture from the air by cooling it and retaining the condensation. Air that enters the dehumidifier passes around a series of cooling coils. As the moisture condenses out of the cooled air, it falls into a reservoir inside the machine. The dried air passes through a heating element as it leaves the dehumidifier.
Basic dehumidifiers have a simple manual power switch. Elite models have more features, including a programmable humidistat that monitors the ambient humidity and turns the machine on or off accordingly. These dehumidifiers are more expensive than basic models.
According to WebMD, chronically humid environments encourage mold growth, which may trigger asthma attacks and other serious respiratory problems. The Mold Source indicates that mold exacerbates allergies and causes sinus infections. Widespread mold growth is difficult and expensive to eradicate, but consistent dehumidifier use prevents the mold from developing in the first place.
Dehumidifier water receptacles must be emptied daily, even if they are not full. If this does not happen, mold has the opportunity to infest the dehumidifier itself. If this occurs, the machine's air return valve spews a constant stream of mold spores out into the surrounding space, intensifying the mold problem.