Dehumidifier vs Air Purifier – Differences + How they Work

Indoor air quality can be affected by not only pollutants but also high moisture content in the air – also called humidity. To improve air quality, an air purifier is the go-to home appliance, but in some cases, you may also need a dehumidifier. What’s the difference between a dehumidifier vs an air purifier?

An air purifier circulates air through its filter and removes pollutants such as odors, pollen, mold spores, and other allergens while a dehumidifier removes moisture from air. A dehumidifier releases cooler, drier air while an air purifier releases cleaner air.

Air purifiers typically don’t cool air unless you’re using a purifier and fan combo or a 2-in-1 dehumidifier and air purifier combo such as the Tenergy Sorbi Air Dehumidifier w/Air Purifying Function.

Is an air purifier the same as a dehumidifier?

An air purifier is not the same as a dehumidifier as they perform different functions. An air purifier is used to remove airborne toxins and contaminants like dust, mold spores, pet dander, and odors while a dehumidifier removes excess moisture from indoor air.

Dehumidifier vs Air Purifier – Differences

Air purifier vs dehumidifier main difference: an air purifier uses filters to clean air and remove pollutants such as pollen, dust particles, pet dander, mold spores, and unpleasant smells. On the other hand, a dehumidifier takes in warm moist air, removes excess moisture, and releases cool, drier air.

Here are the differences between an air purifier and a dehumidifier:

DehumidifierAir Purifier
A dehumidifier lowers humidity levels by taking in warm moist air, removing excess moisture, and releasing cool, drier air.An air purifier filters air to remove pollen, dust, mold spores, bacteria, odors, and other air pollutants.
A dehumidifier cools air because it has a compressor that condenses water from warm air, thus releasing cool air.An air purifier does not make indoor air cooler because it just passes air over filters to remove pollutants.
Use a dehumidifier where relative humidity is higher than 50%.Use an air purifier where there’s need to clean indoor air, especially for allergy sufferers.
Dehumidifiers prevent mold and mildew that thrive when there’s high humidity.Cannot prevent mold from growing in the air, but remove mold spores that already exist in the air.
Dehumidifiers require periodical emptying condensate water when the tank fills up.Air purifiers do not require emptying of water as they do not collect any moisture from the atmosphere.

As you can see from the table above, these two appliances perform different functions that relate to indoor air quality. Depending on your needs, you may only need an air purifier or dehumidifier alone, or even both.

Let’s dive deeper into the differences and how the two appliances work.

Function and mechanism

Dehumidifier vs Air Purifier

The difference between an air purifier and dehumidifier is clear in terms of function and how the two devices deliver it.

  • A dehumidifier condenses excess moisture from indoor air and releases drier air as a result.
  • An air purifier filters out dirt, dust, dander, lint, and other pollutants from air, releasing clean air for breathing.

While a dehumidifier contains a compressor, a coolant, and a water collection tank or drain hose, an air purifier does not collect any water at all. Instead, it can clean indoor air through absorption, adsorption, ionization, or UV light treatment mechanisms.

Mold control

A dehumidifier controls mold and mildew by drying out air and making it not conducive for mold spores to grow while an air purifier filters out mold spores from indoor air to get rid of them.

Both appliances are great for reducing mold and the musty smell that comes with the growth of mold in bathrooms and other indoor spaces.


Most modern home appliances have built-in smart detectors for whatever function they perform.

Dehumidifiers have a dehumidistat while air purifiers have an air quality monitor. When the dehumidistat detects the indoor humidity being higher than the desired (set) level, it turns on the appliance to begin removing moisture from the air.

On the other hand, air purifiers with auto or smart mode have an appliance that continually analyzes the air quality in the house. If it detects dust or other impurities in the air, it automatically switches on the appliance to start cleaning indoor air.

These two functions are fairly similar and can be important features when comparing an air purifier vs dehumidifier to buy for your home.

How a Dehumidifier Works

A humidifier draws in air containing moisture, passes it over condenser tubes where excess moisture is condensed and collected while cool, dry air is released into the room. Some pollutants and allergens are also trapped over the air filters, so a dehumidifier, in a way, cleans air before circulating it back in the house.

Here’s a flow diagram for the dehumidification process:

Here’s how a dehumidifier works:

  1. The machine takes in air through the grille with the aid of a fan.
  2. The warm, moist air passes over very cold pipes circulating with a coolant (Freon).
  3. Water condenses on these pipes and drips into a collection tank.
  4. The moisture-free air passes over a compressor unit for warming back to the original temperature.
  5. The humidifier blows back dry air back into the room.

Note: This process is highly simplified. Dehumidifiers draw water from moist air through either absorption and adsorption or refrigeration. Most appliances have a refrigerant, so they work by condensing water out of moist air and removing it.

High humidity in the house leads to a constant smell of dampness. The musty smell is not the only problem because high relative humidity above 70% provides a conducive environment for mold spores to grow and thrive. Dust mites also thrive in humid areas and can be a health problem to allergic people.

If you live in an area with high humidity, a dehumidifier is one of most important appliances you want to buy especially if you are asthmatic or have any sort of respiratory allergies.

In fact, in a home with high humidity, you’ll notice some black stuff collecting on vents and other surfaces as moisture combines with dust, settles on surfaces, and provides a medium for mold spores to grow.

Some dehumidifiers purify and dehumidify indoor air at the same time. A good example is the bamboo charcoal air purifier that can remove odors, excess humidity, and other air contaminants through a process called adsorption.

Do dehumidifiers make a room cooler?

A dehumidifier improves air quality cleaning it and removing excess moisture content. At the last stage of removing moisture, the device warms the dried-out air to its initial temperature before circulating it back into the room.

If you’d like to make your room cooler, a portable air conditioner or a window AC is the best home appliance to install in your house if. You can use it with a dehumidifier to control indoor air temperature and humidity levels as well.

How an Air Purifier Works

An air purifier comprises a fan that absorbs air and pushes it to pass through a filtration system or media where pollutant particles get stuck. Some air purifiers work by neutralizing toxin particles and as such may not necessarily have a fan.

An example of a bladeless air purifier is the Dyson Cool Air TP02 and TP04 tower designs. However, it is common to find most air purifiers equipped with HEPA filters that filter out very tiny dust particles out of indoor air to improve its quality.

Other methods air purifiers use to clean air is through ionization and UV light disinfection processes.

Here’s a diagram showing how an air purifier works:

Air Purifier and how it works

Do air purifiers dry out air?

Air purifiers do not dehumidify air because they do not have moisture condensation mechanisms that are found in dehumidifiers and air conditioners. The primary function of an air purifier is to remove air contaminants such as dust, pollen, mold spores, pet dander, soot, odors, and other allergens from indoor air.

Therefore, you cannot use an air purifier as an alternative to a dehumidifier. If your indoor air is humid, a good dehumidifier or a combo of an air purifier and dehumidifier is the best device to fix this problem.

Use air purifier or dehumidifier for mold control?

Both an air purifier and a dehumidifier can help with mold control in the house. Damp indoor air provides a great medium for mold spores to grow and feed. Since a dehumidifier helps lower the humidity level, the dried out air is not good enough for mold spores to thrive in. Therefore, a dehumidifier also helps control mold and mildew in the house.

On the other hand, an air purifier is also good at reducing mold in the house. The appliance sucks in air laden with pollutants including mold spores and filters out the contaminants. The air that’s released back into the environment is clean and free of mold spores.

Can you use a dehumidifier and air purifier together?

Both humidifiers and air purifiers have filters that clean up dirty air to remove nano-particles that may affect indoor air quality. However, a dehumidifier works harder when there are a lot of pollutants such as pet dander in the air.

You can use an air purifier and dehumidifier together to reduce the load on each appliance while ensuring cleaner, cooler air even without an air conditioner in the room. However, you cannot substitute one for the other.

Which one to use in the basement?

Basements can have high humidity problems especially in a newly constructed house. If not heated properly, the extra moisture can lead to damage to flooring, ceilings and other surfaces that don’t like water.

Use a dehumidifier in your basement to remove excess moisture that can damage your house. If you spend a lot of time in the basement, you can also use a portable air purifier to clean air and remove pollutants including mold spores.

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