How to Clean a Humidifier (and Keep Mold and Scale Away)

A humidifier can make dry winter air much more comfortable, but a dirty one can spread mold, bacteria and white mineral dust into the air you breathe. The U.S. Consumer Product Safety Commission has long warned that portable humidifiers need regular cleaning. Here's how to clean a humidifier the right way, plus a routine that keeps it fresh.

Quick answer: Unplug it, empty the tank, and soak the tank and base reservoir in undiluted white vinegar for 20–30 minutes to dissolve scale. Scrub with a soft brush, rinse thoroughly, then disinfect if needed with a diluted bleach solution (never mixed with vinegar), rinse again, and air-dry before refilling.

Always Check Your Manual First

Ultrasonic, evaporative (wick) and warm-mist humidifiers have different parts. Some manufacturers recommend specific cleaners or say not to submerge certain parts. Follow the manual where it differs from this guide.

What You'll Need

White vinegar
Soft brush or old toothbrush
Regular unscented household bleach (optional, for disinfecting)
Clean cloths
Distilled or demineralized water (for refilling)

Step-by-Step Deep Clean (Weekly)

1. Unplug and empty

Unplug the humidifier, remove the tank, and pour out all the water. Take out any filter or wick.

2. Descale with vinegar

Pour undiluted white vinegar into the base reservoir and fill the tank partly with vinegar. Swish it around and let it sit 20–30 minutes. Vinegar dissolves the white mineral crust.

3. Scrub

Scrub the base, the tank and crevices with a soft brush. On ultrasonic models, gently clean the small metal transducer disc with a soft brush; never scrape it.

4. Rinse well

Rinse all parts thoroughly with water until the vinegar smell is gone.

5. Disinfect (optional but recommended)

If the manual allows, fill the tank with water mixed with a small amount of bleach (a common guideline is about 1 teaspoon per gallon), let it stand 20 minutes, swish, empty and rinse several times until no bleach smell remains. Never mix bleach with vinegar: rinse the vinegar out completely first, because the combination releases toxic chlorine gas.

6. Dry and reassemble

Let everything air-dry before reassembling. Replace the filter or wick according to the manual.

Daily Habits That Prevent Mold

Empty, rinse and dry the tank every day; refill with fresh water.
Use distilled or demineralized water to reduce white dust and scale.
Keep indoor humidity between about 30% and 50%. Too much humidity encourages mold and musty smells (see how to get rid of musty smell).
Store it clean and completely dry at the end of the season.

Signs Your Humidifier Needs Cleaning Now

Pink or black slime in the tank or base
Musty or sour smell
White dust on furniture near the unit
Reduced mist output

Natural Cleaning Notes

Hydrogen peroxide (3%) is another disinfecting option some manuals allow. Read our hydrogen peroxide cleaning guide for safe use, and never combine it with vinegar in the same container.

FAQ

Can I put essential oils in my humidifier?

Only if the manufacturer says so. Oils can damage plastic parts and transducers in many models.

How often should I replace the filter?

Typically every 1–3 months during use, depending on the model and water hardness.

Is it safe to run a humidifier with mold in it?

No. Clean and disinfect it before using it again.