How to Clean a Humidifier: Daily, Every Third Day and End of Season
A dirty humidifier tank can grow mold and bacteria, and hard water leaves white dust everywhere. Here's the simple cleaning routine the EPA recommends.
Empty, wipe dry and refill a portable humidifier every day, and give it a full clean every third day, which is the EPA’s recommendation. Unplug it, scrub the tank, remove scale, and use the cleaner your manual recommends. If the manual doesn’t name one, the EPA suggests 3% hydrogen peroxide on surfaces that touch water, followed by several rinses with tap water. Fill with distilled or other low-mineral water to cut down on scale and white dust.
Why it matters
Standing water in a humidifier tank is a good place for mold and bacteria to grow, and some humidifiers can send what’s in the tank into the air. Hard tap water also leaves mineral scale inside the unit. Ultrasonic and impeller models can spray those minerals out as a fine “white dust” that settles on furniture. Regular cleaning and the right water prevent both.
What you need
- Your humidifier’s manual (or the manufacturer’s online care page)
- A soft brush or bottle brush, and a clean cloth
- The cleaning or descaling product your manual recommends
- If the manual doesn’t specify: 3% hydrogen peroxide, the kind sold in drugstores
- Gloves
- Distilled water for refilling
Daily: empty and refill
- Unplug the humidifier.
- Empty the tank and base completely. Don’t top off old water.
- Wipe the inside dry with a clean cloth.
- Refill with fresh distilled or low-mineral water and reassemble.
Every third day: clean and descale
- Unplug and take it apart as the manual shows. Keep water away from the motor base and electrical parts.
- Empty and scrub the tank and base with a soft brush to remove film and slime.
- Remove scale. Use the descaler or method the manual recommends. Many manuals suggest soaking scaled parts in white vinegar for a set time, then rinsing. Only do this if yours says it’s safe for the materials.
- Disinfect if needed. Use the product your manual names. If none is given, the EPA suggests 3% hydrogen peroxide on all surfaces that come in contact with water.
- Rinse thoroughly with several changes of tap water so no cleaner gets misted into the room.
- Dry all parts and reassemble with fresh distilled water.
Use one product at a time. Never mix vinegar and hydrogen peroxide in the same container, and never combine bleach with vinegar, ammonia or other cleaners. If you use more than one in a cleaning session, rinse thoroughly with water in between. Some manufacturers allow a diluted bleach solution for disinfecting. Follow their exact dilution and contact time, ventilate the room, and rinse until no smell remains. See cleaning products you should never mix.
If someone swallows, inhales or gets a cleaning product in the eyes, call Poison Control at 1-800-222-1222 (US) or emergency services.
Which water to use
| Water | Mineral content | EPA view |
|---|---|---|
| Distilled | Very low | Preferred |
| Deionized, reverse osmosis or “purified” | Low | Less effective than distilled, but better than most tap water |
| Tap water | Varies; high in hard-water areas | More scale and white dust |
| Spring, artesian or mineral water | Not demineralized | Avoid |
If you see white dust on surfaces near the unit, the EPA says it’s a sign minerals are being released into the air. Switch to lower-mineral water, or check that any demineralization cartridge is working and replace it as the manufacturer directs.
Filters, wicks and cartridges
Evaporative humidifiers use a wick filter that soaks up water. These get crusty with minerals and can grow mold. Replace them as often as the manufacturer says, and sooner if they’re stiff, discolored or smell. Some manuals allow rinsing a wick between replacements; others don’t. Demineralization cartridges in ultrasonic units also need regular replacement.
Mold in the tank
If you find pink, black or slimy growth in the tank, clean and disinfect the unit as above before using it again. If growth is in places you can’t reach or keeps returning, or the unit smells musty even after cleaning, replace the humidifier. Wear gloves and avoid breathing in while scrubbing heavy growth.
Don’t overdo the humidity
A humidifier can create the damp conditions it’s meant to fix. The EPA recommends keeping indoor humidity at or below 50% and measuring it with a hygrometer. If you see water condensing on windows or walls, lower the setting, move the unit or run it less. Damp carpet or tabletops around the unit are another warning sign. Higher humidity also helps dust mites thrive. See condensation on windows and how to get rid of dust mites.
Storing it for the season
- Clean it thoroughly and dry every part completely.
- Throw away used filters, wicks and cartridges.
- Store it in a dry place.
- Clean it again and dust the outside before you use it next season.
The EPA’s Use and Care of Home Humidifiers page covers the full guidance.
Bottom line
Change the water daily, clean every third day, use distilled water, and follow your manual for the cleaner. If the manual is silent, use 3% hydrogen peroxide and rinse well. Never mix cleaners. Keep room humidity at or below 50%, replace wicks and cartridges on schedule, and dry the unit fully before storing it.
FAQ
Can I put essential oils or vinegar in the water tank?
Only if your manual says so. Many manufacturers say not to add anything to the water, because additives can damage parts or be released into the air.
Is tap water OK in an evaporative humidifier?
Evaporative units don’t spray minerals the way ultrasonic ones can, but the minerals collect in the wick. Low-mineral water still reduces scale.
What’s the white dust on my furniture?
It’s minerals from hard water, usually from an ultrasonic or impeller unit. Switch to distilled water.
Can I clean my humidifier in the dishwasher?
Only parts the manual lists as dishwasher-safe. Never put the motor base in water.
