Humidifier Smells Musty? Here's How to Clean It and Use It Safely

It's humidifier season. The heat came on, the air turned dry, someone woke up with a scratchy throat, and the humidifier came out of the closet. A day later, the room has a faint swampy smell, and you're not sure if it's the humidifier or the room.

It's usually the humidifier. A machine that holds standing water in a warm room is a perfect place for slime and smell if it isn't cleaned often. The fix is not hard, but it does have to happen on a schedule.

Water that sits in the tank and base grows a film. You may see it as pink or orange slime, a cloudy coating, or white crust from minerals. The musty smell comes from that film. Running the humidifier then puts that smell into the room along with the moisture.

The other half is the room itself. A humidifier on high in a small bedroom with the door shut can push the room past comfortable into damp. Then the windows drip, the closet wall gets cold and wet, and the smell isn't only coming from the machine anymore.

Unplug it first. Read the manual for your model, because some parts aren't meant to be soaked.

1. Empty the tank and the base. Don't top off old water. 2. Fill the tank partway with white vinegar, or a mix of vinegar and water, and let it sit for about 20 to 30 minutes to loosen mineral crust. Do the same with the base. 3. Scrub with a soft brush. A bottle brush and an old toothbrush get into corners. 4. Rinse very well until the vinegar smell is gone. 5. Let every part dry completely, in the air, before you put it back together. 6. If your model has a wick or filter, check the manual. Most wicks are meant to be replaced, not cleaned forever. A wick that's stiff, brown, or smells should go.

Never mix vinegar with bleach, and don't add oils, scents, or cleaners to the water unless the manual says your model is made for it.

- Empty and refill with fresh water every day. Don't let water sit overnight unused. - Rinse and wipe the tank every day or two, and do the full clean about once a week. - Use distilled water if your manual suggests it. Tap water leaves minerals and can create white dust around the room. - At the end of the season, clean it and dry every part before you put it away. A humidifier stored with water in it will greet you with a smell next fall.

More is not better. A cheap humidity gauge near the bed tells you what's actually happening. If you see:

- Water running down the inside of the windows in the morning, - A damp feel to the bedding, - A musty smell in the closet, - Or a gauge reading that stays high,

then the setting is too high or the humidifier is too big for the room. Turn it down, use it for part of the night, or leave the door open so the moisture spreads out.

Keep it a couple of feet away from walls, curtains, and the crib, on a surface that won't be hurt by a little moisture.

If the humidifier is clean and off, and the room still smells musty, look at the room. Check the window sill, the corners near the floor, behind the dresser, and the closet wall. Our article on a humidifier making the bedroom damp walks through that.

This page is about the machine and the room, not about anyone's health. Coughs, breathing trouble, or symptoms that worry you go to a doctor. Wet walls or a big patch go to a licensed pro.

When Your House Doesn't Feel Right is a picture book that shows where to put a humidity gauge, what a too-wet window looks like, and the other quick room checks one photo at a time. It's $2.99 at https://clearnestair.com/book.