Humidifiers vs. Dehumidifiers: What is the Difference and When You Need One

Dry skin, chapped lips, and itchy eyes—these are only some of the signs that you have dry air in the house. Clammy skin and frizzy hair, on the other hand, may be signs of high humidity. 

Humidity is the amount of water vapor in the air. It is often a product of the climate in a certain geographical location. In weather reports, you’ll see the relative humidity (RH) in percentage. This refers to the amount of water that is actually present compared to the maximum amount the air could hold at a given temperature. 

As the air temperature increases, the air is able to hold more water molecules. When there is a lot of moisture, high temperature feels even hotter. Meanwhile, in the winter season, the cold air is able to hold less water molecules. In consequence, low humidity will make it feel even colder.

The ideal indoor humidity level is around 30-50% RH. Anything above 50% can encourage mold growth and attract pests to your home. Conversely, air that’s too dry can cause dehydration and skin and respiratory ailments. 

To prevent any of these problems, it’s important to maintain the proper environmental conditions inside your house. Find a product or a combination of products that will help you control the temperature and humidity year round. These may include a humidifier and dehumidifier. Some people may need either one, and some may need both, but how do they actually differ from each other?

What’s the Difference Between a Humidifier and Dehumidifier?

Humidifiers and dehumidifiers are completely different products. However, they can be confused for each other since they sometimes have a similar exterior. The main purpose of a humidifier and dehumidifier is to control indoor humidity, and that’s where their similarities stop. In fact, their jobs could not be more different. 

A humidifier increases the humidity level, while a dehumidifier decreases it. The processes in which they operate are also contrasting.

How Does a Humidifier Work?

A humidifier adds moisture to the air. Different types of humidifiers use different methods to do this.

Cool Mist Humidifiers

The most common type is called an evaporative humidifier. It uses a wick filter to absorb water from the reservoir. A fan then blows through the filter, letting the moisture evaporate. This type of humidifier self-regulates. As humidity levels increase, it becomes more difficult to evaporate water.

An ultrasonic humidifier is best used at night because of its nearly soundless operation. It produces a cool mist using high-frequency vibrating metal diaphragm instead of a fan. 

Pure Enrichment MistAire Bedroom Humidifier

Warm Mist Humidifiers

A steam humidifier or vaporizer emits warm mist. It has an internal heater that boils water before releasing the warm steam into the air. This type of humidifier is great for cough and cold symptoms.

How Does a Dehumidifier Work?

A dehumidifier reduces the amount of moisture in the air. They do this through different methods.

Compressor Dehumidifier

Most people are familiar with the compressor-based dehumidifier. A compressor powers the condenser and evaporator to remove moisture and warm the air. A fan draws the humid air and passes it over the cold coils. As the air temperature decreases, it loses its ability to hold moisture. It condenses into water and drips down into the internal tank or out through the drain hose.

Frigidaire FFAP5033W1 Dehumidifier

Peltier Dehumidifier

Another method that mini dehumidifiers use is called thermoelectric cooling or Peltier effect. It is based on the idea that a voltage of electricity creates a temperature difference between the two sides of a Peltier module. Humid air is drawn by a small fan through the cold side on the front of the unit. The moisture condenses and the cold, dry air then passes through the hot side. Warmer, dryer air exits through this side. 

Desiccant Dehumidifier

The other type of dehumidifier is called a desiccant. It uses a substance that absorbs or adsorbs moisture from the air. It comes in a variety of sizes, from disposable packets or tubs, to high-capacity commercial units. The main difference from compressor-based dehumidifiers is the desiccant doesn’t use cooling coils to remove moisture. Instead, moisture is transferred to the desiccant material. This makes the desiccant type ideal for colder temperatures.

Do You Need a Humidifier or Dehumidifier?

The ideal indoor humidity is between 30% and 50%. If you know the typical humidity level inside your house, it will be easier to find which product you need. If the humidity is around 60% or above, then you need a dehumidifier. However, if humidity levels are usually below 30%, then you need a humidifier. 

If you don’t have the exact measures of humidity inside your house, there are some common signs you need to watch out for.

Humidifiers are commonly used in winter when the air is cold and dry. Dry skin, chapped lips, and itchy eyes are often signs of low humidity. It can also cause dehydration, nosebleeds, itchy throat, and other cold symptoms. Prolonged exposure to dry air can lead to drying and cracking of wood. 

On the other hand, if the air feels muggy or you notice a musty smell, these are signs of high humidity. You might see condensation on your windows or damp stains on walls and carpeting. If you find visible signs of mold and mildew growth on furniture and wall corners, this is a sure indicator that you need a dehumidifier .

How Does Humidity Affect Your Health?

Dry air will absorb moisture from any moist surface. This includes your skin, eyes, and airways.  Low humidity can cause nasal passages and throat to become dry and irritated. It can also cause flaking and cracking of skin, which results in itching and bleeding due to scratching. When the air is too dry, tears evaporate fast, leading to dry, itchy eyes, and sometimes even blurred vision. Additionally, some disease-causing bacteria thrive in low humidity.

On the other hand, high humidity makes your home a haven for common allergy and asthma triggers such as mold and dust mites. Touching mold or inhaling mold spores may cause allergy symptoms on people with allergies or asthma and even on otherwise healthy individuals. These symptoms include sneezing, runny nose, eye and skin irritations. Dust mites also thrive in high humidity. These microscopic insects leave waste products that can trigger allergic reactions.

A common sign of humidity is a sticky feeling in the air. This is because the air is saturated and can’t absorb your sweat. You are also at higher risk of dehydration in humid conditions. Humid air is difficult to breathe since it contains high amounts of water vapor and lower oxygen molecules.

Both humidifiers and dehumidifiers help reduce the risks of allergy and asthma attacks by controlling the humidity in your home. Humidifiers are commonly used in winter when the air is dry and cold. Conversely, dehumidifiers are useful during humid summer days or the rainy season in tropical climates.

How Does Humidity Affect Your Home?

Over time, low humidity can cause drying and cracking on wood beams and furniture. Wood loses moisture and shrinks in size. In contrast, wood absorbs moisture and expands when exposed to high levels of moisture.

Mold and mildew thrive in damp environments. They can grow on walls, ceilings, furniture, and almost any surface with excess moisture. They eat away the material, causing damage to furniture, equipment, and your house structure. 

Damp stains on walls, ceilings, and flooring indicate high humidity levels. This can lead to cracks in drywall and gaps between the floor and baseboard. Excess moisture can also result in rotting wood and termite infestation. 


Humidifiers and dehumidifiers both help control indoor air quality, protecting your health and home. In simple terms, a humidifier works to humidify the air or add moisture. A dehumidifier does the opposite—it reduces humidity. 

Finding the appropriate product for your particular needs can help maintain a comfortable range of humidity in your home. Look for the signs to know which one you need.

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