Do Air Humidifiers and Vaporizers Stop Airborne Viruses?

Virus magnifiedWith the viral pandemic spreading across the world some people have asked if humidifiers could have a role in preventing indoor viral transmission.

First and foremost, it’s very important to follow CDC advice and your local medical authorities on prevention.

The actions and effects of humidified air on airborne viruses have been demonstrated and established in previous scientific research though.

This article covers these actions and effects and whether air humidifiers and vaporizers may be beneficial in reducing both airborne virus infectivity and surface viral contamination.

Also ahead, the pros and cons of vaporizers versus humidifiers and which one is best to use in your home for you personally.

How Humidifiers Stop Airborne Viruses

Viruses, like coronaviruses, influenza and rhinoviruses that cause the common cold, can spread in the air attached to microscopic floating water droplets.

An ultrasonic cool mist humidifier, like this one I have in my bedroom, produces humidified air and increases relative humidity (the amount of water vapor in the air) inside your home.

Low indoor relative humidity, particularly common in the cooler months, though also caused by air conditioning, is a major factor in the transmission of airborne viruses.

All of us expel microscopic water droplets known as aerosols when we breathe, and especially when we cough, sneeze and talk.

Normally these aerosols are harmless. However, when a person has a viral infection, like influenza, the expelled droplets will contain these contagious pathogens.

Once floating in the air these harmful microbes can infect others, either directly through the air they breathe, or by spreading over surfaces they subsequently touch.

Why Humidity Matters for Viral Transmission

When the air inside your house or apartment is dry and below 30% relative humidity, aerosol particles, with their viral hitchhikers, quickly evaporate moisture.

This makes them much smaller, and smaller aerosols will remain airborne and therefore infectious for much longer.Viruses closeup

Structural changes within microscopic droplets suspended in relative humidity under 30% also increase viral survivability and infectivity.

However, when indoor humidity is above 40% expelled aerosols maintain or increase their moisture levels, making them both less infectious and less able to float for long periods.

Research Studies on Increasing Humidification to Combat Viral Infection

Numerous scientific studies have shown raising relative humidity, ideally to around 45% to 50% within an indoor environment, can significantly reduce viral transmission rates.

This study on the role of different levels of humidity in relation to viral transmission of aerosols showed:

“At low relative humidity, influenza retains maximal infectivity and inactivation of the virus at higher relative humidity occurs rapidly… Maintaining indoor relative humidity above 40% will significantly reduce the infectivity of aerosolized virus.”

In this research paper, University of Carolina scientists studying SARS-CoV and its behavior on surfaces discovered that viral concentration decreased the higher the relative humidity level in the environment.

This study suggests increasing indoor humidity levels to 50% may be beneficial in significantly reducing the survivability of coronaviruses on surfaces, with the caveat that it was done on the original SARS virus, not SARS-CoV-2.

There are currently no published peer-reviewed studies I’m aware of specifically regarding the effect of humidity on the novel coronavirus.

However, humidifiers have proven effective against viral transmission in previous scientific research and aerosols are the key factor here, not individual virus structure.

Is a Humidifier or Vaporizer Better for Airborne Viruses?

Both air humidifiers and vaporizers increase indoor relative humidity. The methods by which they do it are different though.

The best modern humidifiers use ultrasonic technology to release superfine cool mist into the air.Virus droplets indoor air

Vaporizers, on the other hand, usually heat water releasing steam or warm mist into the surrounding air.

From the sole perspective of decreasing transmission of viral particles on aerosols, raising relative humidity above 40% is the most important factor, according to scientists and infectious disease experts.

Whether you do this with a warm mist vaporizer or cool mist humidifier doesn’t matter, as long as either one is working effectively.

However, there are other factors which can determine whether a humidifier or vaporizer is better for your home and you personally.

Humidifier Pros and Cons


  • Humidifiers, and the humidified air they produce, moisturize your nasal passage, throat and respiratory tract. This helps you breathe easier, aids in protective cilia function in your airway and can ease coughing and a painful sore throat.
  • Dry air increases airway inflammation and the risk of respiratory infections. Breathing humidified air boosts your defenses against colds and flu and other respiratory illnesses.
  • Low humidity air dries out your skin, lips and even eyes, as well as your nasal passages and respiratory tract. Flaky skin, cracked lips, nosebleeds and dry eye conditions often improve with regular use of a good humidifier or vaporizer.
  • Humidifiers help you sleep better by providing the ideal humidity for restful sleeping. It’s important not to increase humidification too much though. A high quality one like this with built-in humidistat and auto set humidity is best for bedrooms.
  • While they many initially cost more than budget vaporizers, humidifiers generally have much lower running costs over the longer term.


  • People who suffer from severe allergies, and in particular asthma, should be cautious about using humidifiers or vaporizers. The American Academy of Allergy, Asthma & Immunology (AAAAI) warns against raising relative humidity above 50% with a humidifier as it could exacerbate asthma or allergy symptoms.
  • Raising relative humidity too much indoors can trigger mold growth and increase the likelihood of dust mites so it’s very important to maintain healthy humidification levels, most commonly cited as between 45% and 50%. This advanced ultrasonic model will adjust automatically to optimal humidity levels. This is essential if you use your humidifier in the bedroom overnight.
  • It’s recommended to use purified and demineralized water in an air humidifier and change it daily. More advanced models, like the one linked above, use a special filter to disinfect water of any germs. If your humidifier doesn’t have a function like this then the water intake needs to be cleaned more regularly, preferably with vinegar rather than chemical cleaners.

Vaporizer Pros and Cons


All of the previously detailed benefits of humidified air apply to vaporizers as well. Used properly they can:

  • Lessen the chance of viral transmission and infection.
  • Help you breathe easier and prevent dried out nasal passages and throat inflammation.
  • Improve your skin and help prevent dry eyes and cracked lips, especially during the colder months of the year.
  • Improve your sleeping patterns and how refreshed you feel in the morning (though humidifiers with auto humidity feature are far superior for this).
  • Since they turn water into steam, you can add essential oils to vaporizers to release them into the air. Antibacterial and antiviral eucalyptus, tea tree and my personal favorite rosemary oil are ideal for this purpose in 2023 with the pandemic.
  • As vaporizers heat water there is less chance of them releasing germs from unpurified H2O into the air. This can be an issue with cheap wick humidifiers that are not cleaned regularly.
  • A steam vaporizer, like this popular little bestseller, are often less expensive than ultrasonic humidifiers. They work best in lounge rooms, studies and other areas where you spend a lot of time during the day.


  • As with humidifiers, vaporizers can raise humidity too high if left running for long periods. It’s recommended to buy a cheap hygrometer at the same time if you choose to get a vaporizer. Keep it near you and switch the vaporizer off if relative humidity goes much over 50%.
  • Since vaporizers heat water to high temperatures they should not be positioned where small children or pets could knock them over.
  • While initially cheaper, electrical running costs are usually higher with vaporizers versus humidifiers in the long run.
  • Unfortunately neither humidifiers or vaporizers work well with negative ion generators, another technology for combating airborne viruses. If you operate an ionic air purifier in the same room then position it at the opposite end to a vaporizer for best results.

In Summary

Using a humidifier or vaporizer to raise the relative humidity in your home to above 40% can dramatically reduce airborne virus transmissibility and infectivity.

While there are currently no peer-reviewed studies on using humidifiers for the reduction of viral transmission of the novel coronavirus, the basic mechanics of how viruses travel on aerosols and how humidity affects them are well understood by science.

Previous research also shows higher humidity reduces viral survivability on surfaces like tables and door handles. Another important factor in preventing transmission and infection.

Humidifiers and vaporizers have many other benefits, particularly in the colder and less humid months of the year, or if you keep drying air conditioning on throughout the day and night.

If you would like to have one in your home I recommend this ultrasonic model I have with built-in humidistat. Set it to keep indoor relative humidity at 45% or 50% for best results.

Alternatively, consider a steam vaporizer, like this inexpensive bestseller. These are great for using essential oils and a much healthier way to freshen the air in your home than harmful chemical air fresheners with their VOCs.

If you do choose a vaporizer, or a cheap humidifier without adjustable humidity function then you really should get a low cost hygrometer too. Keep an eye on it to make sure the humidity doesn’t go much over 50%.

I hope this guide to using vaporizers and humidifiers to reduce airborne viral transmission has been helpful. Remember that social distancing, wearing masks in enclosed areas and washing your hands remains the best protection.

This article may contain affiliate links to products I've researched and recommend. As an Amazon Associate I may earn from qualifying purchases at no cost to the consumer.

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