What Does a Dehumidifier Do?

A dehumidifier, like an air conditioner, dries or removes moisture from the air indoors. Unlike an air conditioner, a dehumidifier does not cool the air.

Dehumidifiers remove some of the moisture from damp air. They help dry out musty, damp basements or can make a room feel more comfortable during humid weather if an air conditioner isn't available.

What It Does

A dehumidifier works much like an air conditioner, drawing moisture out of the air quickly and collecting it, usually in a pan within the dehumidifier. Many models also offer a hose connection to send the water directly into a drain so you don't have to empty the unit yourself. Pump-based versions are also available.

The main difference between an air conditioner and a dehumidifier is that an air conditioner blows out cool, dry air as it removes moisture from the space, while a dehumidifier is not designed to refrigerate the air and discharges warm air. Still, the air may feel cooler and more comfortable in a hot room simply due to less humidity after using the dehumidifier.

When and Where to Use a Dehumidifier

A dehumidifier helps keep the humidity level comfortable in your home. It may be used during humid weather, or in areas that smell musty or show signs of mold and mildew. Mold and mildew are signs of too much moisture, combined with stagnant air. A dehumidifier does not get rid of mold and mildew, but it makes them less likely to occur since it thrives on moisture.


A dehumidifier comes in handy everywhere that dampness is a concern, such as basements and crawl spaces, and enclosed pool or hot tub areas that do not have adequate ventilation.

Humidity and Health

While you may not mind humid or damp conditions in your home, if you or members of your family suffer from asthma or allergies, excess moisture can be cause for concern. Since mold, mildew and even dust mites thrive in humid, damp environments such as damp basements or bathrooms with inadequate ventilation, the best way to help prevent the problems -- besides frequent cleaning -- is to prevent damp conditions in the first place.

The ideal relative humidity in your home is 45 to 50 percent.

Run a dehumidifier in spaces where moisture is a continual problem, or as needed, such as in a basement that sometimes gets damp or wet during excessive rain. A hygrometer helps keep track of indoor humidity so you know when a dehumidifier is needed. For best results, place the hygrometer in areas that often feel or smell damp.

About the Author

Kathy Adams is an award-winning journalist and freelance writer who traveled the world handling numerous duties for music artists. She writes travel and budgeting tips and destination guides for USA Today, Travelocity and ForRent, among others. She enjoys exploring foreign locales and hiking off the beaten path stateside, snapping pics of wildlife and nature instead of selfies.