We all know that feeling of walking outside on a sticky summer day. That damp, oppressive heat can immediately cover your skin and permeate your clothes—and what’s worse is when that humidity pervades your home. Such excess moisture could lead to mildew and mold if not eradicated. This is where dehumidifiers come in. But what do dehumidifiers actually do?

Dehumidifiers are useful for a number of reasons, from personal health to household safety. Depending on where you live, you may benefit from a dehumidifier to improve the air quality of your space and even protect your health.

We turned to the experts to find out exactly what dehumidifiers do and how having one in your home can be a huge benefit.

What Is a Dehumidifier?

As David Cannestra, CEO at Chill Squad Air Conditioning, explains, “A dehumidifier is a household appliance designed to maintain a comfortable and healthy level of humidity by removing excess moisture from the air.” They’re especially useful in typically musty, damp spaces like basements, bathrooms, and laundry rooms.

While they can protect your health by controlling the amount of humidity in your home, they are also a practical tool for preserving the integrity of furniture and fabrics. A well-functioning dehumidifier will ideally maintain humidity levels between 30 and 50 percent. 

Contrary to popular belief, dehumidifiers are not only stand-alone devices. They actually come in all sizes, from portable units suitable for smaller rooms to whole-house systems integrated with HVAC setups.

Remember, though: For all of their might, dehumidifiers are not a cure-all. “While many people think so, dehumidifiers don’t purify the air or prevent all mold growth,” cautions Danny Pen, president of New Era Plumbing & HVAC. “Dehumidifiers can help prevent mold but won’t get rid of it.” Be sure to have an expert properly identify and treat any mold so that you can rest assured that your home is safe from any moisture problems. 

How Does a Dehumidifier Work?

The majority of dehumidifier models are called compressor dehumidifiers, which work through refrigeration. They function by pulling air over cold coils using a fan. “As the air cools, the moisture in it condenses into water droplets much like dew forming on grass,” explains Cannestra. These droplets will collect in a tank or drain away through a hose, while the now drier air passes over warm coils to return to room temperature before being released back into your space. 

Alternatively, desiccant humidifiers use a moisture-absorbing material like silica gel to trap water vapor. Similarly, the collected water is either stored in a tank or drained away, according to Pen. Once dry, the air is released back into the room through an exhaust vent. While either method is effective at lowering humidity, the compressor style is more popular due to its efficiency in warmer conditions, Cannestra notes. 

Conveniently, a number of modern models work automatically, turning on when humidity rises above a set level and shutting down as soon as the desired humidity level is reached.

How Do Dehumidifiers Differ From Humidifiers?

Dehumidifiers are not to be confused with humidifiers. While both improve air quality, they function quite differently. “Dehumidifiers and humidifiers are like two sides of a coin,” says Cannestra. “They both manage air moisture but in opposite ways.”

Put simply, a dehumidifier pulls water out of the air to combat dampness, while a humidifier adds moisture to prevent dryness, which can be helpful, especially during harsh winters when skin and sinuses are negatively affected. “If you’re battling a clammy basement, a dehumidifier may be what you need,” says Cannestra, whereas, “if your home feels like a desert, a humidifier is your friend.”

How to Clean a Dehumidifier

Always unplug the unit before cleaning and check the manual for model-specific tips. For refrigerant, compressor-based dehumidifiers, Penn recommends following these simple steps:

1. Empty the water tank after each use.
2. Wipe it dry with a clean microfiber cloth to prevent mold.
3. Every month or so, remove and rinse the air filter with warm water (most are washable). If yours isn’t washable, you will need to replace it.
4. Let the air filter dry before re-installing.
5. Clean vents every 2-3 months with a soft microfiber cloth and gentle dish soap solution.
6. Inspect and clean the drain hose monthly.
7. Wipe down compressor coils every 6 months with a clean microfiber towel and mild dish soap solution. 
8. For the exterior, clean with a soft microfiber cleaning cloth and a gentle dish soap solution, avoiding harsh chemicals. 

For desiccant dehumidifiers, follow the above protocol, but remember to regenerate the desiccant wheel every 6 months (some models require this, some do not). “Regenerating the desiccant wheel just means drying it out so that it can keep absorbing moisture,” explains Pen. “Most desiccant dehumidifiers have a built-in drying function or a high heat setting that does this automatically.”