Reducing or eliminating the sources of pollutants and ventilating with fresh outdoor air are the most efficient strategies to improve indoor air quality. Additionally, studies indicate that filtration can be a valuable adjunct to source management and ventilation¹. This is when an air purifier and humidifier come into play.

Air purifiers and humidifiers each have a designated purpose and their advantages and benefits. So, let's talk about each of their functions to gain a better understanding.

An air purifier is a device that assists in removing pollutants from the air, including smoke, pollen, pet hair, dust, and pollen. They use filters such as HEPA or activated carbon filters to absorb and trap these particles. 

A humidifier adds moisture to the air to raise the humidity level. It releases water vapor using a water reservoir and a system such as an evaporative wick or ultrasonic technology.

Differences Between Air Purifiers and Humidifiers

Now that you know the basics of how each device works, let's explore the main differences between air purifiers and humidifiers:

• Intended purpose – Air purifiers are made specifically to clean the air and eliminate different pollutants like smoke, dust, and more, while humidifiers are made to put moisture in the air.
• Maintenance – Routine air purifier maintenance usually needs filter changes every six to 12 months. Humidifiers, however, require more frequent upkeep, such as adding water to the device and routine cleaning to stop the spread of bacteria and mold.
• Coverage – In comparison to humidifiers, air purifiers often have a larger coverage area. The size of the device you use will determine how large a room it can cover.
• Cost – Air purifiers tend to cost more, with models that Consumer Reports recommends ranging from $200 to $900 plus regular filter changes². Humidifers, on the other hand, specifically models also recommended by Consumer Reports, begin at around $80³.

Similarities Between Air Purifiers and Humidifiers

While air purifiers and humidifiers have different functions, they share some similarities. In broad terms, both offer:

• Health benefits for individuals with allergies, respiratory conditions, and dry skin issues, as well as babies, children, and people living in dry climates or during winter
• Indoor air quality improvement
• Home comfort 
• Complimentary use in creating a healthy and comfortable indoor environment

Who Should Use Air Purifiers and Humidifiers

Certain groups of people should particularly consider using an air purifier or humidifier, as highlighted below:

• Individuals with allergies or respiratory conditions – Health considerations are among the top factors when deciding to use these devices. An air purifier may help lessen the triggers for respiratory disorders, allergies, or sensitivity to airborne contaminants in you or any household members. A humidifier, on the other hand, might aid with symptoms of discomfort brought on by dry air, such as dry skin, a dry throat, or cracked lips.
• People living in polluted or smoky areas – In these cases, you must consider your indoor air quality needs. An air purifier would be a good option because your primary concern is removing airborne pollutants like dust, pollen, pet dander, or smoke. 
• Those with dry skin or respiratory discomfort – A humidifier would be more suitable if you are concerned about providing moisture to the dry indoor air.
• Children and elderly persons – Due to their immature or compromised immune systems, babies, young children, and older adults are frequently more susceptible to respiratory problems and dry skin. For example, babies often battle coughing illnesses like croup and dry, stuffy noses. Humidifiers or air purifiers can provide a healthier indoor climate for these age groups.
• Individuals in dry climates or during the winter months – When or if you choose a humidifier or air purifier, your choice may be influenced by the climate and season of your location. A humidifier might be more practical in dry locations or in winter when central heating can make the air too dry. An air purifier may be essential to improve interior air quality in places with significant outside air pollution.
• Those looking for overall wellness – Even for those without any particular health issues, air purifiers and humidifiers can help with overall wellness by cultivating a healthier indoor atmosphere, enhancing sleep quality, and lowering the risk of respiratory discomfort or skin problems by dry or poor indoor air quality.

Benefits of Air Purifiers and Humidifiers

Although not all research is consistent, air purifiers, particularly those with high-efficiency particulate air (HEPA) filters, have been shown in some studies to have several health benefits, which include reducing particulate matter in the air⁴, improving lung function, and providing cardiovascular benefits⁵.

To this extent, air purifiers have been proven to be effective in the following ways:

• Removing pollutants and allergens from the air – particularly air purifiers with sufficient CADR (Clean Air Delivery Rate) can reduce indoor PM2.5 (smaller particles) by 50% or more⁶. This helps you by:
  • Reducing symptoms of allergies and asthma by reducing the number of allergens in indoor air⁷
  • Minimizing COPD symptoms and other respiratory issues⁸
  • Lowering the presence of harmful microorganisms such as bacteria and viruses, which may reduce the risk of infections, particularly for individuals with weakened immune systems⁹
• Reduce airborne particles containing viruses(e.g., SARS-CoV-2) – Some air purifiers have reported particle removal efficiencies of up to 99.9% for particles as small as 0.1 microns and recent studies in 2022 have shown the successful reduction of airborne SARS-CoV-2 concentrations in hospitals using combined air filtration and UV sterilization techniques¹⁰
• Improving mental health – Increasing indoor air quality by reducing exposure to pollutants and allergens can also benefit mental health as indoor air pollution has been associated with triggering symptoms of anxiety, depression, and other mental health conditions. Thus, air purifiers may improve mental health outcomes by creating a healthier indoor environment¹¹.

However, the effectiveness of an air purifier in purifying a room depends on various factors, including selecting the suitable model based on the size of the room, ensuring the filter is designed to target the specific contaminants present, regularly changing the filters, and considering the ventilation of the room.

Humidifiers have been proven effective in the following ways:

• Reducing the spread of the flu – A 2013 study concluded that maintaining indoor humidity levels above 43% lowered the infectivity rate of the influenza virus¹²
• Prevent dry skin – A 2008 study in a Japanese hospital discovered that using a humidifier in the winter increased air humidity from 32.8% to 43.9%, which lead to reduced staff reports of dry and itchy skin¹³
• Relieves asthma and allergy symptoms – Increased air humidity levels soothe nasal and throat tissues¹⁴ 
• Reducing nasal congestion by moistening nasal passages/canals – More moisture enables your nasal mucus to be more easily moved by the cilia (the little hairs in your nose), enabling congestion to be blown out
• Improve sleep quality – Humidifiers are commonly incorporated into CPAP machines for sleep apnea patients, due to the dry air blown into the nose by the CPAP machine, which can exacerbate congestion. A 2010 study showed that using heated humidification with CPAP treatment helped alleviate symptoms of nasal congestion in sleep apnea patients¹⁵

The effectiveness of humidifiers is dependent on maintenance practices.

Risks Associated With Air Purifiers

Exposure to Polluted Air Due to Dirty Filters

There have been concerns that dirty or clogged air purifier filters may increase indoor air pollution rather than reduce it. If the filter is clogged, the air drawn into the cleaner might not be cleansed thoroughly and may pick up accumulated particles on the filter. Additionally, blocked and clogged filters reduce the capability of the purifier¹⁶.

Mold and Bacteria

Studies have compared particles found in household dust with those trapped in a HEPA air filter¹⁷ and others types of filter¹⁸, and found that these trapped particles in the filters could create a conducive environment for mold and bacteria to grow and multiply if the filters are not changed regularly. In certain situations, these microorganisms may sufficiently accumulate in the filter to be released into the surrounding environment. 

Ozone Concerns

Some air purifiers use negative ions to clean the air, which is effective¹⁹. However, this process can produce ozone as a byproduct. If breathed in excessively, ozone may irritate the lungs²⁰, reduce lung capacity, and cause them to be more susceptible to bacterial infection²¹. Therefore, it's crucial to be aware of this before buying an ozone-producing air purifier because it might not be appropriate for everyone.

Risks Associated With Humidifiers

Over-Humidification Leading to Mold Growth

A humidifier that releases too much moisture may dampen fabric furniture like mattresses, couches, and draperies, resulting in condensation on the walls and mold development throughout the house. Mold growing in a damp home environment has many health effects²², so humidifier use needs to be tailored to the already existing level of humidity in the air.

Health Concerns

Dirty humidifiers might encourage a ground for bacterial growth, which may result in coughs and colds²³²⁴. Continuously topping up the humidifier’s water without cleaning it can lead to more serious respiratory conditions too, such as hypersensitivity pneumonitis²⁵.

Such risks can be reduced by regularly cleaning your humidifier. However, you must be careful about the chemicals used to do so, as residual amounts left after cleaning and aerosolized may cause health issues as well²⁶.

Burns

Burns are frequently linked to humidifier use, especially when used around children²⁷. Children up to three years old are the most comon humidifer burn victims²⁸. Warm mist humidifiers should not be used in a baby's room. The hot steam can be dangerous, particularly when used next to the baby's cot, as they are more sensitive to changes in temperature.

Tips for Using Air Purifiers and Humidifiers

To preserve their efficiency and avoid any potential detrimental effects on indoor air quality, it is crucial to adhere to the manufacturer's instructions for cleaning and maintaining air filters. The EPA recommends a few guidelines on using air cleaners at home²⁹:

• Clean or change the air filters as the manufacturer directs to ensure that your air purifier provides clean air to your living space.
• Select a portable air purifier with a clean air delivery rate (CADR) sufficient for the room size or area where it will filter particulates. 
• Choose an air cleaner with an activated carbon filter or another gas-filtering device to filter gases.
• Avoid furnace/HVAC filters and portable air cleaners that purposefully produce ozone.

The EPA recommends maintaining your home's humidity levels between 30% and 50%³⁰. Excessive humidity can result in condensation, breeds bacteria and mold, and aggravates allergy or asthma symptoms.

It is recommended that you should clean your humidifier at least every three days³¹. Here are some tips on running your humidifier:

• Use distilled water, not tap water, because the minerals in tap water might encourage the growth of harmful germs inside humidifiers. Additionally, one study found using tap water in an ultrasonic humidifier released particulate matter comparable to a heavily polluted city³². 
• To avoid mold formation, ensure the humidifier's components are completely dry before storing them.
• Empty and replace the water in your tank at least once daily. 
• Use 3% hydrogen peroxide to remove minerals in your humidifier's tank. Then, after cleaning, make sure to rinse the tank to prevent chemical vaporization the next time you use it.
• Changing the humidifier's filter as often as the manufacturer suggests, or more frequently if it gets dirty.
• When using humidifiers with heating elements around children, it's crucial to take additional care and never let them handle the devices and do not keep them in a child's bedroom. A cool mist humidifier is a valuable solution since it increases humidity, which helps children breathe more easily. 

Frequently Asked Questions

Conclusion

In summary, the main difference between air purifiers and humidifiers is in how they function. Air purifiers are intended to improve the quality of the air inside buildings by removing air pollutants. Humidifiers are made to raise relative humidity levels when they are too low in order to enhance the quality of indoor air.

Air purifiers and humidifiers offer great benefits, such as removing pollutants and allergens from the air and improving indoor air quality. Additionally, you can use a humidifier daily to lower pollutant and allergy levels in the air. You can use it sometimes when the air is excessively dry or a household member is sick. However, you should also be aware of potential risks such as over-humidification leading to mold growth, ozone concerns, or even humidifier burns.

Most importantly, consider individual needs when acquiring an air purifier or humidifier. Take into account each device's maintenance needs. While humidifiers need routine water replacement and cleaning to avoid bacterial or mold growth, air purifiers often need to have their filters changed regularly. Consider the cost, time, and maintenance effort while selecting your choice.

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Marion Sereti

Marion is a freelance health and wellness writer with a passion for all things digital health. She loves diving deep into the latest research and trends in the industry and distilling them down into fun, relatable pieces that people can relate to. Whether you're a health nut or a tech geek, she is always looking for new and interesting ways to help readers access quality and evidence-based information.