Many homeowners struggle to understand the key differences between air purifiers and humidifiers, so if this sounds like you, then you're not alone. 

Simply put, air purifiers clean the air, while humidifiers add moisture to it.

From my years of experience, I’ll break down how each works, their effects on air quality, and when to use them to meet your needs.

Comparing air purifiers and humidifiers (Key differences)

For babies: Both can be beneficial

Both humidifiers and air purifiers can be beneficial for babies, but for different reasons.

Air purifiers can help remove airborne pollutants and irritants like dust, pollen, pet dander, dust mites, and other allergens. 

This is great for babies with sensitive skin or respiratory issues like allergies or asthma.

Humidifiers can help add moisture to the air, which can benefit babies with dry skin or nasal congestion.

Dry air can make it hard for babies to breathe and exacerbate skin issues like eczema. According to Johns Hopkins Medicine, up to 20% of babies worldwide will have eczema. 

Ultimately, whether to use an air purifier or a humidifier for your nursery will depend on their specific health needs and the air quality in your home.

Related article: Humidifier placement guide

For allergies: Get an air purifier

Air purifiers are generally best for alleviating allergy symptoms. Airborne pollutants like dust, pollen, pet dander, and mold spores are filtered out of the air using an air purifier.

In fact, air purifiers with a HEPA filter can remove up to 99.7% of particles up to 0.3 microns in size. 

However, some allergies can also be caused by dryness of the nose, throat, and sinuses.

A humidifier can help alleviate these symptoms by adding moisture to the air and soothing irritated mucous membranes.

Always use air humidifiers properly to avoid the growth of mold and bacteria that can worsen allergy and asthma symptoms. You should always consult your doctor to determine how to manage your allergies.

For asthma: Depends on your triggers

My son has asthma, so airborne pollutants and low moisture levels can trigger his symptoms. An air purifier can help with asthma if airborne pollutants are the trigger. 

If the trigger is low moisture levels, a humidifier can alleviate asthma symptoms by adding moisture to the air.

Both a humidifier and an air purifier are sometimes necessary for managing asthma. This is partially because asthma triggers can be tricky to pinpoint, especially for patients who see changes in asthma symptoms based on the weather. 

For mold: Avoid humidifiers at all cost

To prevent mold growth, it’s important to avoid using humidifiers. 

This is because mold thrives in moist environments, and excessive moisture in the air can contribute to the development and spread of mold. 

Air purifiers can effectively remove airborne mold spores, which can be a common trigger for allergies and respiratory issues. 

So if you’re dealing with mold problems, using an air purifier and avoiding humidifiers is your best bet.

If you're dealing with high humidity and mold, I recommend looking into an air purifier and dehumidifier combo unit to help reduce moisture levels. 

For eczema: Humidifiers can help

Low humidity can cause the skin to become dry, itchy, and flaky, exacerbating conditions like eczema. Using a humidifier can combat dryness in the air and improve eczema.

You should look for a humidifier designed to improve skin hydration and prevent dryness.

Cool mist humidifiers, like ultrasonic humidifiers, are generally recommended for use with itchy skin. 

Ultrasonic humidifiers produce a fine mist that can be easily absorbed by the skin.

Related article: How ultrasonic humidifiers work

For cough: Depends on your triggers

A persistent cough and cold symptoms can be caused by several factors, including poor air quality and dry air.

Airborne pollutants like dust particles, mold, pollen, or pet dander can irritate the respiratory system and trigger coughing. 

In this case, using an air purifier can help improve your cough by eliminating these harmful particles and improving air quality.

However, dry indoor air can also irritate the throat, nose, and sinuses, leading to a persistent cough. 

In such cases, using a humidifier can help alleviate your cough. Adding water droplets to the air can soothe irritated mucous membranes and reduce coughing.

Related article: What type of water should I use in a humidifier?

For dust and dust mites: Get an air purifier

While a humidifier is an excellent tool for adding water droplets to the air and improving indoor air quality, it is not designed to filter out airborne particles like dust.

Therefore, an air purifier is a better option for combatting dust in the home.

Air purifiers use filters to trap and remove these particles, making the air cleaner and healthier to breathe. 

When to use an air purifier versus a humidifier?

Knowing when to use a humidifier versus an air purifier depends on the symptoms you’re dealing with. 

For example, if you’ve noticed that your skin tends to be drier during winter, humidifiers can come in handy.

The humidifier will add moisture back into the air to help alleviate dry skin and other discomforts like dry nasal passages.

Unlike humidifiers, used mainly in the winter, air purifiers are used all year round.

That’s because indoor air pollutants don’t take any time off and can accumulate no matter the season. 

From dust and pet dander to mold spores and pollen, these particles can cause discomfort and even health problems for some people year round.

If you suffer from seasonal allergies, consider using an air purifier with an HEPA filter, at least during pollen season.

Related article: Whole house air purifiers reviewed

As the wind carries pollen from trees and grasses into your home, an air purifier can help filter out those airborne allergens and reduce your symptoms.

Cost differences of air purifiers and humidifiers

When it comes to cost, there’s a big difference between humidifiers and air purifiers.

Humidifiers are generally pretty affordable and can cost less than $100, depending on the model you choose. Whole house humidifiers will cost most, ranging from $150 to up over $1000 depending on the model and installation.

Air purifiers tend to be more expensive, and you could spend upwards of $500 for a top-of-the-line air purifier.

However, budget-friendly air purifier brands are available that can cost as little as $100.

The initial cost is not the only thing to consider when buying an air purifier, though.

Replacement filters for HEPA and activated carbon filters must be changed several times a year.

These costs can add up to over $100 annually. So, deciding between an air purifier or a humidifier is important to factor in the total cost of ownership over time.

Air purifier basics and working principle explained

It’s all in the name: an air purifier is designed to purify the air that surrounds it.

It cleans the air by drawing in air molecules and passing them through multiple stages of filtration. There are a few filtration stages, each one targeting a different issue.

Most air purifiers start the filtration process with a prefilter where large airborne pollutants like pet hair and dander are removed.

Then comes the carbon filtration stage, which works to remove odors.

Finally, there’s HEPA filtration, which is responsible for removing those tiny particles that the previous stages missed.

There are a few more methods of filtration used in modern air purifiers, but these 3 – prefilter, carbon, and HEPA – are the most common.

When an air purifier uses the filtration method described above, it’s called passive purification.

There are also active purifiers, which work by releasing negatively charged ions into the air to remove airborne pollutants from the air. These, however, carry the change of releasing ozone.

When deciding between the two, passive purifiers are more efficient, effective, and safer.

Related article: Air purifiers versus ionizers

Do I need an air purifier?

I believe everyone could benefit from investing in a home air purifier, even if it’s just a small portable air purifier.

An air purifier will rid your room of indoor air pollution, helping you breathe easier.

So do you really need one? For some people, myself included, the answer is yes.

There are a few tell-tale signs to look out for to see if you should invest in an air purifier:

ACLAB Note:

You can get an air quality meter to test the whether you actually need an air purifier or not. If the meter shows AQI, or Air Quality Index, to be beyond normal range, then you will benefit from an Air Purifier.

Basic humidifier working principle explained

A humidifier is a device that is designed to add moisture back into the air.

To use a humidifier, you’ll start by filling up the water tank. Once the machine is turned on, it will start working to turn the liquid into airborne moisture and then release that moisture into the surrounding air.

The exact steps for how the internal components of a humidifier work depend on the type. The 2 most common types of humidifiers on the market today are:

No matter which one you go with, using a humidifier comes with a lot of benefits.

Related article: Differences between evaporative and ultrasonic humidifiers

Do I need a humidifier?

I live in a pretty wet climate, so I don’t need a humidifier.

If you’re not sure if you should invest in a humidifier, the easiest way to find out is to measure the moisture levels in your home.

The ideal humidity level is somewhere between 30 percent and 50 percent.

Here is a data table showing what your relative humidity range should be, depending on your goals:

If you can’t test your humidity, there are a few more signs that it’s time to start using a humidifier:

Related article: Best humidifiers for sinus relief

Can you use an air purifier and a humidifier together?

I always get asked if using a humidifier and air purifier in the same room is possible.

The good news is that you can use an air purifier and a humidifier together, and there are some benefits to using both together.

Air purifiers filter out harmful particles and humidifiers add moisture to the air to combat dryness and help soothe symptoms related to dry air. 

You can benefit from both functions by using an air purifier and a humidifier in the same room.