Unplug it first. Every day, empty the tank, wipe all surfaces dry and refill it. Every third day, scrub off any scale, deposits or film. Use the cleaner your humidifier’s manual names; if it doesn’t name one, wipe every surface that touches water with 3% hydrogen peroxide, then rinse several times with tap water. Fill it with low-mineral water such as distilled, and keep indoor humidity at or below 50% (EPA).
The cleaning schedule
| When | What to do |
|---|---|
| Every day | Unplug, empty the tank, wipe all surfaces dry, refill with fresh water. Console models: change the water as the manufacturer says. |
| Every third day | Unplug, empty, scrub the tank and inside surfaces with a brush to remove scale, deposits and film, then wipe dry. Disinfect as the manual says, or with 3% hydrogen peroxide, and rinse well. |
| End of the season | Clean it as the manual directs, throw away used filters, cartridges or cassettes, and make sure every part is dry before storing it somewhere dry. |
| After storage | Clean it again and dust off the outside before using it. |
For portable humidifiers, from the EPA’s Use and Care of Home Humidifiers. Console and furnace-mounted humidifiers: follow the manufacturer’s directions, and don’t let water stand in a tank for long.
How to clean a humidifier, step by step
- Unplug it from the outlet before you empty or clean it (EPA).
- Empty the tank and take the parts apart as your manual shows.
- Scrub the tank and every inside surface with a brush or scrubber, removing scale, deposits and any film on the sides (EPA).
- Disinfect. Use the cleaning or disinfecting product your manual recommends. If it doesn’t recommend one, clean every surface that comes into contact with water with a 3% solution of hydrogen peroxide (EPA).
- Rinse thoroughly with several changes of tap water, so no cleaning chemicals end up in the mist (EPA).
- Wipe every surface dry, put it back together and refill it with low-mineral water (EPA).
The EPA’s method is the default; your humidifier’s manual comes first. Follow the maker’s instructions for its cleaning products, and for using, maintaining and replacing any filters, wicks or cartridges that came with it (EPA).
Why cleaning matters
Microorganisms often grow in humidifiers with tanks of standing water, and studies show ultrasonic and impeller (“cool mist”) humidifiers can disperse microorganisms and minerals from the tank into the air. Breathing mist containing these pollutants has been linked to a kind of lung inflammation. Young children, older adults and people with lung disease or respiratory allergies may be especially susceptible. Following the care steps reduces that risk (EPA).
If you get breathing symptoms you think are linked to using the humidifier, even when you clean it as directed, stop using it and see your doctor (EPA).
Which water to use
Tap water contains minerals. Ultrasonic and impeller humidifiers are very efficient at spraying them into the air as a fine “white dust,” and the minerals build up as scale, where microorganisms can grow (EPA). So the EPA suggests:
- Bottled water labeled “distilled”, which usually has fewer minerals than tap water. Distillation removes minerals most effectively.
- Water labeled “spring,” “artesian” or “mineral” hasn’t been treated to remove minerals.
- Demineralization cartridges, cassettes or filters if your humidifier came with them or its maker recommends them. How well they work varies; white dust means minerals are getting through.
How humid to keep the room
Don’t humidify above 50% relative humidity: more can encourage mold and dust mites. A hygrometer from a hardware store measures it, and some humidifiers have a built-in humidistat you can set. If water condenses on windows, walls or pictures, move the humidifier, turn it down or use it less, and don’t let the area around it, or carpets, drapes and tablecloths, get damp (EPA).
Keep steam vaporizers out of children’s reach: the steam and boiling water can cause burns (EPA).
Questions people ask
How often should you clean a humidifier?
Empty, dry and refill a portable humidifier every day, and clean it every third day (EPA).
What can I use to clean my humidifier?
What your humidifier’s manual recommends. If it doesn’t say, the EPA suggests a 3% hydrogen peroxide solution on every surface that touches water, rinsed off with several changes of tap water.
Can I use tap water in a humidifier?
You can, but the EPA suggests low-mineral water, such as bottled distilled water, especially in ultrasonic and impeller humidifiers, which spray tap-water minerals into the air and build up scale.
What is the white dust from my humidifier?
Minerals from the water, dispersed into the air by ultrasonic or impeller humidifiers. Distilled water or a demineralization cartridge reduces it (EPA).
How do I store a humidifier for the summer?
Clean it as the manual directs, throw away used filters and cartridges, dry every part and store it somewhere dry. Clean it again before you use it next season (EPA).
Sources
- U.S. Environmental Protection Agency, Use and Care of Home Humidifiers (fact sheet; PDF version June 2022): the daily and every-third-day routine; unplugging; 3% hydrogen peroxide when the manufacturer gives no cleaner; rinsing; low-mineral and distilled water; white dust; humidity at or below 50%; storage; steam vaporizer burns; health effects.