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How Do Air Purifiers, Humidifiers and Dehumidifiers Compare?

girl watching humidifier

There are many different appliances that can change and enhance your indoor air quality.

Three of the most common are air purifiers, humidifiers, and dehumidifiers. These machines are common sights in American homes, but each has a specific purpose. Understanding how they operate, therefore, is essential if you want to have the healthiest possible air in your house.

To help you improve the indoor air quality in your home, let’s take a closer look at air purifiers, humidifiers, and dehumidifiers. With a strong understanding of each technology, you can decide which is right for your home and your family!

Air Purifiers

ej HEPA filter efficiency

Air purifiers are designed for one specific purpose: to clean the air. Indoor air is often full of toxins, allergens, and contaminants that aggravate the lungs and cause significant health issues. These contaminants can be especially problematic if people in the home suffer from allergies or asthma. Contaminants and particles come from multiple sources such as pets,smoke, cleaning chemicals, and candles.

An air purifier, however, works to remove these contaminants from the air. By circulating air through an internal filter, air purifiers remove microscopic particles, collecting the contaminants in special filters, such as activated carbon filters or fine sieves. The air purifiers pull air into their filters, where contaminants are trapped and held in place. The purifier then releases clean air into the room.

There are different technologies used in air filters, and many of them are surprisingly unique. You will generally not find these in humidifiers or dehumidifiers:
  • UV light, for example, is used in some air purifiers. UV light kills bacteria and viruses; when it’s used in tandem with a physical filter, it can be extremely effective for purifying air.
  • Another technology used in room air purifiers is activated carbon. Filters using activated carbon, which has a high surface space thanks to microscopic pores, is extremely effective for trapping gases and odors.
  • Air ioniser. Some air purifiers have an air ionizer that introduces positive or negative charges into a room.

happy girl in bedroom

When and Where to Use an Air Purifier

An air purifier can be useful any time of year, in any room of the home. However, during the months that the home is closed up, such as cold winter months and extremely hot summers, air purifiers will be the most useful. When the house is closed tight, fresh air is not allowed in; while this is helpful for insulation, it can trap the harmful contaminants found in the air.


There is a wide price range for air purifiers. Some models, such as the mod jr. cost less than $300, while larger models that are effective for commercial spaces can cost over $1,000.


The maintenance for air purifiers is pretty simple and straight-forward. For most models, all you’ll need to do is replace the filter on a routine basis. Some models have filters that can be washed and dried, while others will require a filter replacement, usually costing around $50 to $150, depending on the model. Most will need to be replaced every six to nine months, while others need to be replaced annually.


humidity level

As you might have guessed from the name, humidifiers add moisture to the air. The purpose of humidifiers is to raise the humidity levels in a house, creating healthier homes and avoiding issues caused by dry air.

Why Use a Humidifier

Dry air can cause a wide range of health issues. Most of them are minor irritants, such as dry or itchy skin, a bothered nose, or a dry throat. Other problems, however, include cracked lips, bloody noses, and sinus congestion.

moisturize dry skin

The purpose of a humidifier is to get your humidity level above 30%.

Types of HumidifiersThere are many types of humidifiers, and each one works in a unique way. In most cases, humidifiers work by releasing a mist into the air, so the products are divided into two categories: warm mist and cool mist.

Warm Mist Humidifiers

  • Steam Humidifiers: This is a basic type of humidifier that releases steam into the air. It has a reservoir of water and can be enhanced with aromas or antibacterial agents. However, steam humidifiers can be hot, so they are not recommended for a child’s room.

Cool Mist

  • Wick Humidifier: Sometimes referred to as an “evaporative” humidifier, these machines have a wick that draws water from a reservoir and a fan that blows moisture off the wick and into the air.
  • Impeller Humidifier: Using a rotating disc that throws water against a diffuser, this type of humidifier essentially separates water into tiny droplets and sprays them into the air. It creates a fine foggy mist that is effective for humidifying a large area.
  • Ultrasound Humidifier: This type of humidifier vibrates to create an ultrasonic frequency. (You can’t hear ultrasonic sound.) The vibrations create water droplets, which are pushed into the air with a fan.

There are also different sizes and strengths of humidifiers. You can find humidifiers, using either warm or cool mist systems, that are designed to humidify a small area or an entire home. Whole-house humidifiers can be places in any room of the home; with good air circulation, they will send moisture throughout the entire house. There are also systems that can be installed directly into the HVAC system, providing proper air humidity through the ducts and vents.

When to Use a Humidifier

We’ll start with the obvious: use a humidifier when the air is dry. (Pretty insightful!) But how can you know if the air is dry? In most areas, the winter presents a time when indoor air is dryer, because of furnaces. If you are running your furnace or a space heater, it’s wise to start using a humidifier.

Where you live can also play a factor. If you live in a colder city, like Boston or Minneapolis, you will have drier indoor air in the winter. However, people in Miami rarely use a furnace; in this case, you’ll want a dehumidifier. (See below for dehumidifier information.)

You can also test the air to see if it is dry. By purchasing a hygrometer, you can test the air’s humidity levels. In most cases, you’ll want a relative humidity level around 30 to 50%, and some experts have said that 45% is the ideal humidity for room temperatures. According to, the proper level is 40 to 50%.

If the humidity goes above 50% you may create mold or mildew. Dust mites can also thrive with higher humidity levels.

Will They Purify Air?

While humidifiers are useful for adding moisture to the air, they are not effective for cleaning the air. If you need to clean and purify the air, the best solution is a room air purifier, which can be used at the same time as a humidifier.


Humidifiers are often very affordable. You can go to a big box store or home improvement store and find humidifiers under $50. There are, of course, larger whole-home units that cost above $100, and you can spring for units that cost around $300. According to, if you want to install a built-in home humidifier, the average cost is $450. But for the most part you can find items for a very affordable price.

Risks with Humidifiers

There are a few slight risks involved with the use of humidifiers. With warm-mist products, there is the chance for burns, so children should never be allowed to handle these humidifiers.

Humidifiers can also release too much moisture, creating condensation on walls and windows, which could lead to mold. Dirty humidifiers can also release bacteria into the air, so regular cleaning is essential.


While humidifiers are fairly easy to maintain, they will require regular attention. Cleaning is very important. About once a week, thoroughly rinse and wash the water reservoir in your humidifier. Use vinegar or a mild detergent to clean the inside of the unit, and be sure to rinse completely and dry before placing the reservoir back in the humidifier.

Depending on the unit you purchase, you may also need to replace parts, such as evaporative wicks, discs, or filters.


running water moisture

While humidifiers release moisture into the air, dehumidifiers serve the opposite purpose: they take moisture from the air, creating drier conditions. By taking humidity out of the air, these units reduce the growth of mold, spores, and other contaminants that grow in damp conditions.

Why Use a Dehumidifier?

There are many reasons for using a dehumidifier in your home. One of the top benefits is the removal of moisture, creating an atmosphere that is less receptive to mold and mildew. They can also help reduce odors by removing the musty smell that often comes from mold. There is even speculation (although little proof) that dehumidifiers can reduce energy bills because the A/C unit works harder when it has to cool damp air.

Types of Dehumidifiers

There are multiple types of dehumidifiers, ranging from units that act much like your refrigerator to highly-sophisticated units that are used to dry water-damaged buildings.

silica gel


This is a fairly simple dehumidifier that pulls air over a cold coil, which then collects condensation and allows it to drip into a collection tub. Using the same cooling principles as a household refrigerator, this is also the most common type of dehumidifier that you will find.

Absorption Dehumidifiers:

These dehumidifiers absorb moisture from the air by rotating a “desiccant,” a chemical substance that creates dryness in its vicinity. Silica gel is a common desiccant. These units rotate the desiccant and release dryer air into the room.


This type of dehumidifier uses a heat pump to create a cool surface where condensation is collected. These units are quiet but can use a lot of energy, making them more expensive to operate.

Dehumidifiers can also be classified by their specific purpose or general size, as opposed to the technology they use. Portable dehumidifiers, for example, are smaller and can be used to lower humidity in one specific room. Basement dehumidifiers, on the other hand, are powerful units designed to reduce moisture in a large, damp basement. There are also whole-home dehumidifiers, which are capable of removing up to 100 pints of water a day!

When and Where to Use a Dehumidifier

Small living spaces with limited ventilation, such as bathrooms, small apartments, or basements, are common areas where moisture can build up, even in dry climates.

Will They Purify Air?

According to Allergy Consumer Review, dehumidifiers do not really clean the air in your home. By removing moisture, dehumidifiers can make the air less friendly to mold and mildew growth, but they do not purify.

They don’t reduce contaminants, such as pet dander, chemicals, or radon, and they will not remove mold spores that are already present; they’ll simply create an environment that is less friendly to mold and mildew. Although dehumidifiers do have an air filter, this is mostly to keep dust from landing on the coils.


The price of dehumidifiers is generally more expensive that humidifiers, largely because the act of removing water from the air is more complicated that adding water to the air. (Think about it: when you boil water, you’re humidifying the air!)

You should expect to pay between $150 to $250. You can also find industrial units that cost thousands of dollars, but these are usually purchased by companies that specialize in mold mitigation and water-damage cleanup. There are also dehumidifiers for small rooms, like bathrooms and closets, that only cost about $50.

Risks with Dehumidifiers

Dehumidifiers are no more risky than other appliances you have in the home, but they do have a few issues. Because many in-home dehumidifiers use freon to cool the coil (the same chemical used in refrigerators or air conditioners), there is a potential risk of leaking chemicals.

Even when most products use a closed system, freon could still leak. Outside of potential electrical fires, which any appliance can cause, this is the only concern for household dehumidifiers.


Dehumidifiers have a small reservoir that holds the collected water. If not emptied, this reservoir could overflow, and if not properly cleaned, it can become a breeding ground for mold, which is somewhat ironic, since the appliance is designed to reduce mold.

Check the reservoir regularly and empty as needed, and be sure to clean and sanitize about once a week. If the dehumidifier has a filter, you should also replace this according to the manufacturer’s recommendations.

Comparing Air Purifiers, Humidifiers, and Dehumidifiers

Which is Best for Allergies and Asthma?


When it comes to preventing allergies and asthma problems, air purifiers are without a doubt the most effective choice. Humidifiers have little to no benefit for allergies or asthma, and could even irritate symptoms when over-used, while dehumidifiers simply make it harder for mold and mildew to grow.

Dedicated air purifiers are widely accepted as the most effective home and office appliance for cleaning air and reducing allergies and asthma problems.

Air Purifiers, Humidifiers and Dehumidifiers: What’s the Bottom Line?

After all that, what’s the bottom line? How should you use air purifiers, humidifiers, and dehumidifiers?

In general, humidifiers and dehumidifiers should be used as needed to maintain healthy moisture levels in your home’s air.

Air purifiers, however, should be used constantly.

Whether the air is too moist or too dry, there will be allergens and other airborne contaminants in your home, so the need for constant air cleaning remains, no matter what the current humidity levels. When used alongside air purifiers, humidifiers and dehumidifiers are part of the strategy for a clean, healthy home.

Amazing Purifiers for a Cleaner Home

If you are looking for a world-class air purifiers, check out the large selection for Oransi. We have small air purifiers for single rooms are large commercial grade units for cleaning spacious offices.

No matter what your specific needs, Oransi has an air purifier for you and your family!

Want to learn more about cleaning your air? We recently wrote this guide on how to choose an air purifier.