Use and Care of Home Humidifiers | US EPA (2023)

Tips for the Use and Care of Home Humidifiers

  • Empty the tank, wipe all surfaces dry, and refill the water in portable humidifiers daily to reduce any growth of microorganisms.
  • Use water with low mineral content, such as distilled water, to prevent releasing minerals into the air.
  • Clean portable humidifiers every third day to reduce the buildup of scale and microorganisms.
  • If you use a cleaning or disinfecting agent to clean your humidifier, rinse the tank thoroughly to avoid releasing chemicals into the air.

A PDF version of this publication is available: Use and Care of Home Humidifiers (pdf) (1.97 MB, June 2022)

On this page:

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  • Introduction
  • Types of Humidifiers and Associated Pollutants
  • Recommendations for Use and Care
  • Can I Use Tap Water in My Ultrasonic or Impeller Humidifier?
  • Additional Sources of Information

On other pages:

  • Biological Pollutants’ Impact on Indoor Air Quality
  • Indoor Particulate Matter
  • The Indoor Microbiome


Humidifiers are commonly used in homes to relieve the physical discomforts of dry nose, throat, lips, and skin. The moisture they add to dry air also helps alleviate common nuisances brought on by winter heating, such as static electricity, peeling wallpaper, and cracks in paint and furniture. However, excess moisture can encourage the growth of biological organisms in the home. These organisms include dust mites, which are microscopic animals that produce materials causing allergic reactions to household dust, and molds.

Several studies have shown that ultrasonic and impeller (or "cool mist") humidifiers can disperse materials, such as microorganisms and minerals, from their water tanks into indoor air. Proper care and cleaning of ultrasonic and impeller humidifiers are important for reducing potential exposures to microorganisms, such as bacteria and molds. Microorganisms often grow in humidifiers which are equipped with tanks containing standing water. Breathing mist containing these pollutants has been implicated as causing a certain type of inflammation of the lungs.

Using water with lower mineral content will reduce exposures to these materials (see Can I Use Tap Water in My Ultrasonic or Impeller Humidifier?).

The young, the elderly, and those people with lung diseases or respiratory allergies may be particularly susceptible to certain types of airborne pollutants. However, if you follow the recommendations for the use and care of home humidifiers provided in this fact sheet, the potential for dispersal of microorganisms and minerals from your humidifier should be reduced.

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Types of Humidifiers and Associated Pollutants

Console humidifiers are encased in cabinets which are designed for floor use.

Portable humidifiers are smaller and more readily moved.

Central humidifiers are built into heating and air conditioning systems, and humidify the whole house.

The two types of humidifiers which generally appear to produce the greatest dispersions of both microorganisms and minerals are:

  • Ultrasonic, which create a cool mist by means of ultrasonic sound vibrations.
  • Impeller, or "cool mist," which produces a cool mist by means of a high-speed rotating disk.

Two additional types of humidifiers can allow for growth of microorganisms if they are equipped with a tank that holds standing water, but generally disperse less, if any, of these pollutants into the air. These are:

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  • Evaporative, which transmit moisture into the air invisibly by using a fan to blow air through a moistened absorbent material, such as a belt, wick, or filter.
  • Steam vaporizer, which create steam by heating water with an electrical heating element or electrodes. "Warm mist" humidifiers are a type of steam vaporizer humidifier in which the steam is cooled before exiting the machine.

Note: Steam vaporizer and evaporative humidifiers are not expected to disperse substantial amounts of minerals.

Recommendations for Use and Care

It is important to use a humidifier only when conditions require it, to use the correct moisture setting for existing conditions, and to clean it thoroughly.

The possible health effects resulting from the dispersal of microorganisms and minerals by home humidifiers are not fully understood. Meanwhile, it may be prudent to reduce the potential for personal exposures to these materials by taking the following precautions, particularly when using ultrasonic and impeller humidifiers.

  • Empty the tank, wipe all surfaces dry, and refill the water in portable humidifiers daily to reduce any growth of microorganisms; follow the manufacturer's instructions for changing water in console humidifiers. Be sure you unplug the unit from the electrical socket first.
  • Use water with low mineral content to prevent the build-up of scale and the dispersal of minerals into the air. See Can I Use Tap Water in My Ultrasonic or Impeller Humidifier? for information on using water with low mineral content.
  • Clean portable humidifiers every third day. Empty the tank and use a brush or other scrubber to clean it. Remove any scale, deposits, or film that has formed on the sides of the tank or on interior surfaces, and wipe all surfaces dry. Again, be sure you unplug the unit.

Follow the manufacturer's suggestions on the use of cleaning products or disinfectants. In the absence of specific recommendations, clean all surfaces coming in contact with water with a 3% solution of hydrogen peroxide. If you use any cleaning or disinfecting agent, rinse the tank thoroughly with several changes of tap water to prevent dispersal of chemicals into the air during use.

  • Follow the manufacturer's directions on cleaning and maintaining console and central (furnace mounted) humidifiers. In particular, if the humidifier contains a tank, do not allow water to stand in the tank for extended periods of time, and keep the water clean.
  • Keep steam vaporizer humidifiers out of the reach of children. Steam and boiling water may cause burns.
  • Do not humidify to indoor relative humidity levels exceeding 50 percent. Higher humidity levels may encourage the growth of biological organisms in the home. Hygrometers, available at local hardware stores, may be used to measure humidity levels. Some humidifiers contain a built-in humidistat which may be adjusted to the proper moisture level. If water condenses on windows, walls, or pictures, relocate the humidifier, lower its humidistat setting, or reduce its use.
  • Do not permit the area around the humidifier to become damp or wet. If dampness occurs, turn the output volume of the humidifier down. If the humidifier output volume cannot be turned down, use the humidifier intermittently. Do not allow absorbent materials, such as carpeting, drapes, or tablecloths, to become damp.
  • Follow the manufacturer's instructions regarding the use, maintenance, and replacement of any materials supplied with the humidifier. Use appropriate materials as recommended by the product manufacturer.
  • Clean the humidifier, as directed, at the end of the humidifying season or when the product will not be in frequent use. Before storage, make sure all the parts are dry. Dispose of all used demineralization cartridges, cassettes, or filters. Store the unit in a dry location. After storage, clean the unit again and remove any dust on the outside.
  • Stop using your humidifier and contact your physician if you have respiratory symptoms which you believe are associated with periods of use of your home humidifier, even if you are following maintenance directions.

Can I Use Tap Water in My Ultrasonic or Impeller Humidifier?

Researchers have documented that ultrasonic or impeller humidifiers are very efficient at dispersing minerals in tap water into the air. In addition, some consumers are bothered by a "white dust" that may appear on surfaces during use of these devices. Most importantly, minerals in tap water may increase the development of crusty deposits, or scale, in humidifiers. Scale can be a breeding ground for microorganisms. Retarding the growth of scale is the most compelling reason to find alternatives to tap water. For this reason, or if white dust is a problem or you wish to minimize your exposure to minerals in the tap water as a matter of prudence, you should either:

  1. Use bottled water labeled "distilled." While distilled water still contains some mineral content, it will likely contain lower mineral content than most tap water. Distillation is the most effective method for removing minerals from water.

Two additional demineralization processes, deionization and reverse osmosis, remove most of the minerals from water, but are generally less effective than distillation. Water demineralized by these two processes would, on the average, be expected to contain a higher mineral content than distilled waters. "Purified" water may be produced by any of these three or other similar processes.

Be aware, however, that not all bottled water is produced using demineralization processes. Bottled waters labeled "spring", "artesian" or "mineral" have not been treated to remove mineral content.

  1. Consider using demineralization cartridges, cassettes, or filters if supplied or recommended for use with your humidifier.

Be aware, however, that the ability of these devices to remove minerals may vary widely. Further research is needed to determine how well, and how long, these devices work. Watch for the appearance of "white dust," which would indicate that minerals are not being removed.

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Also, in areas of the country where the mineral content in the tap water is high, using distilled water may be less expensive than cartridges, cassettes, or filters.

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Additional Sources of Information

For additional information on home humidifiers and other consumer products, contact the U.S. Consumer Product Safety Commission (CPSC) or see the CPSC Safety Alert Dirty Humidifiers May Cause Health Problems.


What maintenance does a humidifier need? ›

Maintaining Your Humidifier

For daily humidifier users, clean your humidifier every few weeks to prevent mineral buildup. All you need to clean the unit are cleaning cloths, a soft brush and either white vinegar, bleach or a mineral cleaning solution.

Do all humidifiers need to be cleaned daily? ›

Without regular cleaning and maintenance, your humidifier can turn into a vicious, festering cesspool of bacteria and mold. Not the kind of stuff you want to be breathing in. Fortunately, maintenance is pretty easy, if you do it often enough. Most humidifier manufacturers recommend a weekly cleaning cadence.

How many years should you keep a humidifier? ›

They keep the relative humidity level at the proper percentage and work to keep indoor environments healthier, ensure that processes run smoothly, and protect against damage to sensitive materials. Depending on the frequency of maintenance and quality of water, a humidifier will have a life expectancy of 10-15 years.

Can I run vinegar through my humidifier to clean it? ›

But never fear, that's the grime we're here to conquer. Unplugged, fill the base of the humidifier with 1 cup of water and 1 cup of white vinegar and leave it to sit for an hour. The vinegar is a natural cleanser and it'll help loosen any residue and disinfect the small unit.

Do whole house humidifiers cause mold? ›

If not used properly, here are some issues a whole house humidifier can cause: Excessive moisture can causes mold growth. Moisture can accumulate within your ducts, causing mold to form and then be distributed throughout the air in your home.

How do I keep my humidifier mold free? ›

To prevent the growth of mold and other contaminants, we recommend rinsing, towel-drying, and refilling your humidifier's tank with fresh water daily. Once a week the tank and the base's well need a deeper cleaning and sanitizing. Replace filters and wicks according to the maker's recommended schedule.

What happens if you don't wash a humidifier? ›

Without regular cleaning, the parts of your humidifier that come into contact with water can develop mold and bacteria growth. In visible mist humidifiers, mold spores and bacteria can potentially be released in the mist.

Do I need to open window when using humidifier? ›

When the weather outside is cold, the air is usually dry. Opening the window during dry, cold weather will reduce humidity levels inside the home or office and would be counter-productive. Keep the windows closed during cold weather and use a humidifier to keep humidity levels optimal.

Where should a humidifier be placed in a house? ›

With a whole house humidifier, choose the most central room in your home, which is usually the living area. The idea is to get the unit where it can distribute the most humidity into the largest areas of the house. Placing the unit near a cold air return will help distribute the humidified air more thoroughly.

Where should you not put a humidifier? ›

You should avoid putting your humidifier near air vents, in direct sunlight, and close to electronic devices. As humidifiers vaporize water and expel it in the air, placing it near electronic devices can lead to short circuits, which is a safety hazard.

Should a whole house humidifier run all the time? ›

If you're monitoring the humidity levels in your home, it's relatively safe to run your humidifier around the clock. You should take special care not to leave anything running while you're out of the house. However, just because it's safe doesn't mean that it's necessary.

Can I use tap water in my humidifier? ›

Tap water is the default for most CPAP users when they go to fill up their humidifier water chambers. But CPAP manufacturers and clinicians recommend that patients use only distilled water. It may seems like an inconvenience, but it's really not, and it's definitely worth it!

Should I put vinegar in my humidifier? ›

Fill the tank with water as you normally would, but add 2 tablespoons distilled white vinegar, too. Let this mixture sit in the tank for 30 minutes. Put the tank on top of the reservoir and let the water drain through like it normally would. Let it stand for another 30 minutes.

Should I put hydrogen peroxide in my humidifier? ›

Hydrogen peroxide is a powerful disinfectant perfect for cleaning the bacteria from your humidifier. You should follow your doctor's instructions if you have lung issues like COPD or pneumonia.

How quickly does mold grow in humidifier? ›

These small crevices can get moldy quite quickly if they are not cared for correctly or cleaned thoroughly. In fact, mold can start to form inside of a humidifier in as little as two days! These mold spores may be nearly invisible to the naked eye.

What is humidifier lung? ›

Humidifier lung (HL) is a relatively rare form of hypersensitivity pneumonitis (HPs) associated with the inhalation of moisture from humidifiers contaminated by various organisms. Because many of the past studies were case reports, clinical characteristics of HL have not been well described.

What can I add to my humidifier water? ›

Add White Vinegar: Fill your humidifier with water, distilled or otherwise, and also add a cup of white vinegar to the tank. This will help prevent any mold from growing. Humidifier Tablets: You can also purchase humidifier tablets to drop into the tank. They dissolve in under ten minutes and can have aromas!

How do you disinfect a humidifier without vinegar? ›

To save time you can skip the vinegar and treat everything with a 4-1 solution of water and 3% hydrogen peroxide. Simply soak the tank, nozzle, and other removable parts for 20-30 minutes and then rinse well with fresh water.

Do humidifiers damage your furnace? ›

If you have a portable personal humidifier in your home, it could be affecting your heater. “We've had a lot of calls of the same problem,” explained Tim Hatfield, Owner of Tim's Heating & Cooling. “Of getting their bumping limit, which is the furnace getting too hot and shutting itself off.”

Can a home humidifier make you sick? ›

But be cautious: Although useful, humidifiers can make you sick if they aren't maintained properly or if humidity levels stay too high. If you use a humidifier, be sure to check the humidity levels and keep your humidifier clean. Dirty humidifiers can breed mold or bacteria.

Are whole house humidifiers healthy? ›

It's not good for your home or your health when the air is too dry, but it's also not good when the air is too moist. (“Everything in moderation” really applies here). If a whole house humidifier is not monitored correctly and properly maintained, there's the risk of adding too much moisture to the home.

Is there a humidifier that doesn't get moldy? ›

The special thing about Vicks's Germ-Free Humidifier, though, is that it uses an ultraviolet beam to prevent microorganisms, bacteria, and mold from growing in the water within the plastic casing of the humidifier, and also from being vaporized out into the air.

How often should you clean your humidifier with vinegar? ›

Empty, rinse, and dry the base and tank every day. Once a week, get rid of any mineral buildup with vinegar or another solution suggested by the manufacturer, and disinfect the humidifier with a 10% bleach solution (follow the instructions for your specific model).

How often do I need to clean my humidifier if I use distilled water? ›

Once you are using purified or distilled water, you should clean your humidifier every 1~3 days. Humidifiers help improve air quality, but they have to be maintained well.

Can bacteria grow in a humidifier? ›

CPSC has found that bacteria and fungi often grow in the tanks of portable and console room humidifiers and can be released in the mist. Breathing dirty mist may cause lung problems ranging from flu-like symptoms to serious infection.

Do whole house humidifiers waste water? ›

Some statistics suggest that many models waste an average of 5 to 8 gallons of water for every gallon of moisture added to the air. With the average output of a home humidifier in the range of 7 to 8 gallons per day, that equates to wastage of almost 2,000 gallons of water per month!

How often should you service your humidifier? ›

Like all mechanical equipment, your humidifier should be serviced at least one time per year and that time is now. As the temperatures go lower, so does the moisture content of the air.

What happens if you don't clean your humidifier? ›

Without regular cleaning, the parts of your humidifier that come into contact with water can develop mold and bacteria growth. In visible mist humidifiers, mold spores and bacteria can potentially be released in the mist.

How do you know if your humidifier has mold? ›

You should also look for any visible mold growth or musty smells in the area around the humidifier. Mold spores will latch onto surfaces like rugs or walls underneath and around the unit. Another sign that mold may be growing is a musty odor emitting from the humidifier.

Is it OK to leave water in humidifier? ›

Letting Water Sit in Your Unit. Never let water sit in the machine for days between uses as a film can form on the top, which can breed bacteria in the enclosed tank. Always empty water and clean the tank when not in use or even when skipping use for one day.

When should I turn off my whole house humidifier? ›

A central humidifier can be a very worthwhile investment, helping to improve the quality of the air in your home during the winter season. Once the weather begins to warm up, though, it is essential to turn off the humidifier in your home until the heating season starts up again in the fall.

Can you use a humidifier all year long? ›

Despite what you think or hear, you can run your humidifier all year round! The benefits of humidifiers extend far past winter and they can be very helpful devices in spring, summer and fall. So just because winter is over doesn't mean you have to pack away your humidifier until next year.

Should I clean my humidifier with bleach or vinegar? ›

To get into any tight crevices, use undiluted vinegar and a toothbrush to scrub away scale. To disinfect the machine, let a solution of water and a small amount of bleach sit in the tank for 20 minutes, then rinse the machine until the smell of bleach is completely gone. Viola—your humidifier is now germ-free.

Can you clean mold out of a humidifier? ›

The simplest way to clean mold out of a humidifier is to use 3% Hydrogen Peroxide. Pour a mixture of four parts water to one part hydrogen peroxide in the tank of your humidifier. Give it a good shake and let it sit for at least half an hour. Pour it out and rinse the tank with water.

How often should you change the water in your humidifier? ›

How often should I change the water in my humidifier? Your water should be changed on a daily basis. Always use Distilled water this help prevent calcium build up in your water chambers and in the prevention of sinus infections. Always rinse your humidifier chamber out before adding new water.


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