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Air Purifier VS Humidifier: What’s The Difference?

Sheryl Cannes
Updated on: November 18, 2022

Pure air or humid air—which one is better? Or, more accurately, which one do you need? Air purifiers and humidifiers perform different functions, yet they’re both designed to improve the air quality of your home. Understanding their key differences can help you determine which one you need or if you need a combo model that performs both functions.

Key Differences Between Air Purifiers and Humidifiers

 Air PurifiersHumidifiers
Removes allergensx 
Removes indoor air pollutantsx 
Removes odorsx 
Kills bacteria and virusesx 
Humidifies dry air x

Air Purifiers: Pros and Cons

No matter how meticulous your housekeeping, the air inside your home carries impurities, contaminants, and various particulates you may not want to breathe in. Indoor air can carry up to two to five times more air pollutants than outdoor air, according to the Environmental Protection Agency. Those impurities or pollutants can range from harmless dust particulates to volatile organic compounds (VOCs) from paint or adhesives.

Air purifiers remove impurities, contaminants, and allergens from the air using one or more purification methods. The purification method determines what kind of particulates, fumes, or odors the air purifier targets.

Types of Air Purifiers

Mechanical Filter

Mechanical filters are made of highly fibrous materials that trap air contaminants as the air purifier pulls the air through the filter. The most effective type of mechanical filter is a high-efficiency particulate air filter, also called a HEPA filter or true HEPA filter. HEPA filters clean the air of particulates down to .3 microns in diameter. That’s small enough for many common allergens like pollen, dust, and pet dander.

Activated Carbon

Activated carbon filters are treated with oxygen to open the carbon’s pores. Those open pores can then absorb fine airborne particulates from pet odors to smoke. While activated carbon filters can absorb many tiny particulates, they can’t absorb all fumes. For example, activated carbon will not remove ammonia or formaldehyde fumes.

Ultraviolet Germicidal Irradiation (UVGI)

These air purifiers use ultraviolet radiation (UV rays) to kill bacteria and viruses. However, they can kill a limited variety because the virus or bacteria are only exposed to ultraviolet light for 20 to 30 seconds. Yet, many bacteria and viruses require at least 5 to 60 minutes of exposure to be destroyed. UV air purifiers can potentially release ozone, which consists of three oxygen molecules fused together. High amounts of ozone can irritate the lungs and decrease air quality. It’s actually a key component of smog and not something you want in your home.

Photocatalytic Oxidation (PCO)

PCO purifiers use ultraviolet rays and hydroxyl radicals to oxidize and neutralize certain gases. However, their use is controversial because they’ve been found to be ineffective by the EPA, and the process creates pollutants of its own, including ozone.

Electrostatic Ionizers (Negative or Positive Ions)

Electrostatic ionizers, also known as ionizers, release charged ions that attract and attach to air particulates. The weight of the ions causes the particulates to fall out of the breathable air space. Some ionizers have electrostatic plates to which the charged particulates are attracted, making them easy to remove. Others leave the particulates to fall to the floor or onto furniture. In the case of the latter, you have to vacuum or wipe off the particulates to completely remove them.

Ozone Generators

Ozone generators release ozone into the air, changing the chemical composition of some air pollutants. However, ozone causes respiratory and lung irritation, putting this type of air purifier on the “no-go” list.

Air Purifier Pros

Air purifiers can make a huge difference in air quality, especially for people with allergies or asthma. While they cannot remove all allergens or air contaminants, the best air purifiers can drastically improve indoor air quality. Air purifiers can:

  • Remove common allergens like pollen, mold spores, dust mites, and pet dander
  • Kill some harmful bacteria and viruses
  • Neutralize odors

Air Purifier Cons

As great as air purifiers can be, they do come with their downsides, including:

  • Running 24/7 to maintain the air quality
  • Can be loud even at night unless they have a sleep mode
  • Must be run in an appropriately sized room
  • Cannot remove or kill all contaminants
  • Take up floor space
  • Some types may reduce air quality

Humidifiers: Pros and Cons

Humidifiers release moisture into the air to prevent or relieve nasal, airway, and skin irritation caused by low humidity. Moistened air can help loosen the mucus and respiratory problems associated with the common cold or flu.

Types of Humidifiers

Humidifiers come in many sizes, shapes, and designs. How and when (summer versus winter) you want to use the humidifier influences the best humidifier for your situation.

Central Humidifiers

Central humidifiers humidify an entire house. They are large, heavy, difficult to move, and expensive. However, if you need to humidify an entire household, a central humidifier is the most efficient way to go about it. They’re a good solution in a dry, arid climate where year-round humidification may be needed.

Evaporators (Evaporative Cool-Mist Humidifier)

Evaporators or evaporative cool-mist humidifiers use a fan to pull air through a moist wick filter. As air passes through the filter, it’s humidified and blown back out of the humidifier. These models are inexpensive but do require filter maintenance.

Impeller Humidifiers (Cool-Mist Humidifier)

Impeller humidifiers, sometimes called cool-mist humidifiers, have a rotating disc that flings water through a diffuser. The diffuser then breaks up the water into tiny droplets that are small enough to float in the air. These models don’t require filter maintenance, but because they use cold water, they must be carefully maintained to prevent mold, mildew, or bacterial growth.

Steam Vaporizers (Warm Mist Humidifiers)

Steam vaporizers have a heating element that boils water to release steam. Vaporizers require less maintenance than a cool-mist humidifier because the heat kills mold, mildew, and bacteria to which a cool-mist model is more susceptible. However, they pose a risk of burning or scalding if the humidifier gets knocked over.

Ultrasonic Humidifiers

These humidifiers use ultrasonic vibrations to break up water and release tiny droplets into the air. They’re quiet and don’t require a filter. However, like other cool-mist models, there’s a greater risk of mold, mildew, and bacteria growing in the water.

Humidifiers Pros

  • Can be run as needed
  • Warm-mist models can be used with essential oils
  • Can relieve dry nasal passages, airways, and skin
  • Relieve congestion associated with common cold or flu

Humidifier Cons

Air Purifier/Humidifier Combos: The Best of Both Worlds

Homes can easily get cluttered with single-use devices. Adding an air purifier and humidifier combo streamlines the look and cuts down on the number of different devices in the home. One device with two functions saves you space and money.

There are a few features to think about before you jump aboard the combo wagon:

  • Tank Capacity: The humidifier’s tank capacity should be large enough that you only need to refill it once a day.
  • Coverage Area: Both air purifiers and humidifiers are designed to work within a specific square footage. Make sure that the air purifier/humidifier is designed for the room’s square feet. If the combo model is too small, it won’t efficiently clean the air or maintain consistent humidity. However, a humidifier that’s too big could cause excess water vapor, which promotes mold and mildew growth.
  • Speed Settings: Speed settings make a difference in how quickly the unit can pull air through for purification and manage humidity. More speed settings give you better control. For example, during the summer, seasonal wildfires may increase smoke, so you would need to increase the speed of the air purifier’s fan. During the winter, you may need to reduce the air purifier’s fan and increase the speed of the humidifier’s to keep the cool winter air at a comfortable humidity level.
  • Type of Air Purification: HEPA filters are best for allergies, while activated carbon filters work best for odor neutralization. Know what you want to remove and make sure the combo has a purification system that targets the right particulates.
  • Extras: Some combo units have sensors that detect the room’s humidity levels and air pollutants. It can automatically turn on and off to maintain a healthy environment. You may also want a model with a remote control to give you flexibility when adjusting settings.


Do I need an air purifier/humidifier combo?

Air purifier/humidifier combos are a great option if you need both functions. For people with asthma or severe allergies, a combo unit provides flexibility based on your climate, changing outdoor air pollution conditions, and pollen levels. However, if you live in a humid climate where humidity levels stay between 30 to 50 percent, a combo unit probably isn’t necessary.

Do humidifiers make allergies worse?

Humidifiers can help or hinder allergies, depending on where you live and how they’re used. The right humidity levels, which fall between 30 to 50 percent, can help prevent some particulates from entering the breathable air. The right humidity levels also prevent dryness of the nasal passages, airways, and throat, which can alleviate allergies.

However, if the humidifier releases too much humidity, it can promote mold and mildew growth, which can worsen allergies.

Are humidifiers worth it in a humid climate?

No. In general, you don’t need a humidifier if you live in a humid climate because the humidity naturally stays in the humidity sweet spot of 30 to 50 percent. If you live in a climate where the humidity is regularly over 50 percent, you may want a dehumidifier to prevent mold and mildew growth.

The Takeaway

Clean air helps maintain a healthy respiratory tract. Air humidifiers and purifiers can remove pollutants and humidify the air, sometimes with a single device. However, your health challenges and the unique characteristics of the climate in which you live can help you determine which device, if any, can best remove dust particles or prevent dry skin for a healthier, more comfortable living environment.


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