While a dehumidifier's job is to remove excess moisture from indoor air, it also removes some odors, especially if the odor is due to those damp conditions. If your basement smells musty, a dehumidifier helps dry the air, reducing odors often caused by mold and mildew spores in excessively damp air. In order for a dehumidifier to successfully remove a moisture-related odor, however, the source of the problem must be treated; otherwise, a continual moisture issue means a continual source for musty odors. If water backs up into the basement every time it rains hard, there's a good chance mold and mildew are growing in the basement as well, causing a continual odor.
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Dehumidifying Damp Spaces
A portable dehumidifier sucks the excessive moisture out of the air, depositing it into a tray or through a hose and into a drain. When it's humid outside, indoor air naturally becomes more humid as well. It's more noticeable during weather when you aren't running an air conditioner or a heater, as these devices sometimes dry the air out a little.
If you've ever been to a cottage or cabin used only a few months a year and open the door for the first time in many months, you've probably noticed a musty or stale odor in the air, or even trapped in the furniture. If you live in a humid area or near a major body of water, you may have noticed such odors in your own home after returning from a vacation. Moist air holds odors, and that moisture and odor end up clinging to all sorts of surfaces, including mattresses, dresser drawers, and window coverings. Running a dehumidifier in such a place helps remove these odors, and it may even remove other lingering odors trapped in that moist air, such as smoke smells from a fireplace.
A small, portable dehumidifier is best at removing odors from one room; it won't de-funk the entire house. If you live in an area that's humid most of the time, a whole-house dehumidifier helps keep the air free of musty odors while also helping prevent mold and mildew indoors. A whole-house dehumidifier connects to an existing HVAC system and uses much of the same ductwork.
Add Fresh Air and Sunshine
Any dark space without ample air flow is far more likely to harbor lingering odors, especially of the musty variety. Imagine two basements: one with windows that open and that allow sunlight and airflow in, and another with shades always over any windows, and those windows never open. The sunnier basement with at least occasional airflow is less likely to smell bad than one that's kept dark and cool and with no source of fresh air. The same holds true for bedrooms kept closed up and dark, versus opening windows and shades and letting sunlight and outdoor air freshen the space from time to time. Sunshine and fresh air help eliminate odors.