Humidifiers Get Gross Fast. Here’s How to Clean Them. | Reviews by Wirecutter

Oct 14, 2024

By Thom Dunn

Thom Dunn is a writer focusing on home heating and cooling. He once blew up a power strip with a space heater and a Marshall half-stack.

After reviewing this guide, we’ve added some clarifications and updated several links. We still stand by all of our advice.

Humidifiers can be an essential comfort tool. They can also be disgusting. 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.

The maintenance schedule is demanding, but the work itself is pretty easy, especially if you do it consistently. Here’s how we go about it over the course of testing and living with lots of humidifiers.

Setting up a consistent usage routine can head off more-serious cleaning issues before they develop.

Try distilled water. Tap water usually has ample minerals and microbes that can develop into a biofilm. To slow this process, the Mayo Clinic echoes most humidifier instructions with the suggestion to fill your tank with distilled or demineralized water. Whatever water you use, don’t leave it sitting in there between uses.

Empty and air out the humidifier whenever it’s off. Stagnant water promotes film growth. And even if you tend to run your humidifier until the tank is empty, you should still manually empty it, shake out residual water, and let it dry completely. Make sure the side of the tank doesn’t have any invisible slime.

Consider a treatment. You can also discourage organism growth by adding a bacteriostatic treatment from Essick Air or a Protec Humidifier Tank Cleaner. We tested these, and though they seemed to inhibit growth, they’re not a substitute for regularly emptying the tank or doing weekly maintenance.

Most humidifier manufacturers recommend a weekly cleaning cadence. The Environmental Protection Agency suggests that you clean and disinfect a humidifier every three days. Most humidifiers have specific how-to guidance in the user manual. Here is some general advice we’ve found works for most models.

Take it apart and rinse all the plastic pieces. Just make sure not to immerse any of the parts with electronic components. Check the user manual if you have any questions or concerns about which parts should or should not come apart.

Find and remove buildup. Once you’ve disassembled your humidifier, look for chalky white buildup on some of the pieces. This is limescale from minerals in your water, and it needs to go. To get rid of it, make a diluted acid mix of white vinegar, citric acid powder, or a similar weak acid. We mix about 2 tablespoons of vinegar per half gallon of water. Wet a sponge or brush with the solution and scrub to dislodge all the gunk. Make sure you get the awkward corners, too—we try to recommend models that are easy to clean, but some tanks are frustrating to deal with.

Soak the stubborn stuff. Sometimes that sediment just won’t budge. We usually just pour vinegar (or your weak acid of choice) right into the crusted spot in the tank or tray and let it soak like that for about 20 minutes. When we go at it again with the brush or sponge later, the soak usually does the trick.

Rinse and air-dry the pieces. You may need to run the humidifier with clean water for a bit to eliminate the leftover vinegar scent.

Although vinegar or citric acid helps with the visible limescale, it doesn’t kill off mold or many other microbes. You need to disinfect the whole unit once or twice a month. It’s overdue if your humidifier starts smelling dank. You can go about it a few ways, depending on how gross or contaminated things have gotten.

Use a solution of bleach or hydrogen peroxide to scrub all of the parts. We recommend following the CDC’s guidelines for this sort of disinfecting solution. No matter what you do, do not mix vinegar and bleach together. Like with the limescale scrubbing, make sure you get all those awkward crevices. If any stubborn growths still don’t go away after a good scrub, try soaking the plastic parts in your disinfecting solution.

Take it outside to run a disinfecting solution through it. If a humidifier is extraordinarily disgusting, running the CDC’s disinfecting solution through the machine can help clear growth from internal components. Important point: The “outside” part is key here. Bleaching your indoor air is a bad idea.

Air it and dry it. Once you’re confident that everything is clean and disinfected, rinse all the parts off and let them dry again.

Evaporative humidifiers like the Vornado EVDC300 use a filter or wick to help carry water from the tank to the fan. Even with regular maintenance, you still need to replace the filter every three to six months. Here’s how to maximize its lifespan.

Remove the filter every time you turn your humidifier off and set it out to dry. You can also let your humidifier run for about an hour without any water until the filter dries out. Either way, this is particularly important if you plan on turning your humidifier off for more than a day. While most filters come with antimicrobial coatings to discourage growth, you shouldn’t let a damp filter sit in the dark for days at a time.

Swish the filter around in cold water. Doing this along with the weekly maintenance helps release any minerals that have built up on the filter. Don’t be concerned if you notice some brown slimy stuff sliding off—that means you’re doing it right. Let it soak for a bit to loosen up the gunk while you clean other humidifier parts.

Do not use any bleach or chemical solutions on the filter. Aside from the aforementioned breathing risks, disinfecting chemicals like bleach can also destroy those antimicrobial coatings on the filter—which sort of defeats the whole purpose of disinfecting in the first place.

This article was edited by Harry Sawyers.

Thom Dunn

Thom Dunn is a staff writer at Wirecutter reporting on heating, cooling, and other home-improvement topics. Sometimes his curiosity gets the best of him, such as when he plugged a space heater and a Marshall guitar amp into the same power strip. Pro tip: Don’t do that.

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