Not Knowing How to Clean a Humidifier Is Actually a Big Deal—Here’s Your Guide to Keeping It Pristine

According to Tim David, CEO at Airlucent, those who constantly run a humidifier should be cleaning it at least once a week to prevent a build-up of mold and bacterial growth. Many of the humidifiers AD tested also include recommendations from the manufacturers to clean the appliances at least once a week.

However, Steve Leasure, vice president of operations at Rainbow Restoration, recommends that you clean your humidifier daily. “At the end of each day, pour out the water, wipe down all surfaces, and refill the tank with distilled water,” he says. Leasure suggests a more thorough cleaning every three days. The Environmental Protection Agency (EPA) advises cleaning humidifiers every three days to prevent the growth of mold and bacteria.

According to Dr. Jie Zhao, head of Delos Labs, you should always unplug the humidifier before cleaning. “This is important especially for ultrasonic humidifiers, since they can disperse minerals and microorganisms into a space,” Zhao says. Also important to note when it comes to cleaning a humidifier: Never mix bleach with vinegar and other acidic cleaners, and never mix hydrogen peroxide with vinegar. In fact, to be on the safe side, don’t mix bleach or hydrogen peroxide with anything but water.

According to Shavers, there are several things you can do to keep mold out of your humidifier. “Replace the filter at the start of each heating season, and rinse the reservoir regularly,” she says. She recommends using distilled water instead of regular tap water, as the former reduces the mineral buildup that feeds mold growth. In addition, if you use the humidifier a lot, she recommends wiping it down weekly to stop mold spores from forming. “A consistent cleaning schedule ensures your humidifier adds healthy moisture to your home instead of harmful contaminants.”

Dr. Zhao advises against the use of essential oils in humidifiers. “A key concern is that the essential oils can be made into small droplets by the oscillation process, and then they can be released into the air with the water droplets,” he explains. “These [essential oil] droplets have a much higher concentration by weight and volume compared to the natural evaporation of the oils through normal use.” He points to the American Lung Association’s findings around prolonged exposure to high concentrations of essential oils being linked to negative heart issues and lung symptoms.

The cleaning methods are basically the same and distilled white vinegar (or your preferred cleaning solution) can be used in both types of humidifiers, per Zhao. “The only difference is you also need to replace the wicks or filters of the evaporative humidifiers following the manufacturer’s instructions.”

Rubino adds that as a general rule, the filter can be swished in clean water and then laid out to dry while the other parts are soaking. “But toss the filter if it’s time for a replacement,” he says.

In addition, David says that you may need to descale an ultrasonic humidifier more often due to their vibration mechanism, which leaves a buildup of mineral deposits. This is particularly important if you live in an area with hard water.

Many (if not most) owner’s manuals advise against the use of tap water in a humidifier.

David recommends using distilled or demineralized water in both warm mist and cool mist humidifiers to minimize mineral buildup and bacterial growth. However, Dr. Zhao recommends using purified water in ultrasonic humidifiers.

Some droplets may deposit on surfaces near the humidifier (such as furniture, floors, or walls), potentially leading to uneven humidification across the room, Dr. Zhao explains. “Water droplets in the mist released from the humidifier will contain any impurities that are present in the humidifier tank, including minerals and germs.” And if your home water has a lot of impurities, he says the droplets may form sticky-white dust on surfaces or furniture. In addition, if the water contains mold, bacteria, or other pathogens, the mist may spread them throughout the room.

According to Rubino, the ideal humidity level in a home should be between 35 and 50 percent. “Too high or too low humidity indoors can cause wellness issues and problems with the home’s health, like mold growth and structural issues.” For example, he says mold tends to thrive at a relative humidity of 60 percent. “With this in mind, only use a humidifier when necessary and as long as the indoor humidity remains between 35 and 50 percent.” Rubino also recommends purchasing a humidifier with a hygrometer and humidistat, which will turn the machine off when it reaches the ideal humidity level to avoid over-saturating the air.

And even with one of the best humidifiers, placement is an important factor. “When using a humidifier, keep it away from porous materials like carpets, cloth furniture, bedding, clothing, or curtains,” Rubino warns. “If these items stay damp, they allow microbial growth to develop in the room.

If you’re using the humidifier to try to remove smoke and other contaminants from the air, consider using an air purifier to improve your indoor air quality instead.

Rubino recommends finding a humidifier with a built-in filter if possible. “The filter will help prevent blowing contaminants into the air, and will also reduce mineral deposits that can negatively impact the machine’s performance and act as a food source for microbial growth.”

Leasure recommends inspecting your humidifier’s wick and filter for mold or signs of wear. “Refer to the humidifier’s manual for any special instructions,” he says. “If it’s time to replace the filter—typically every three to six months—toss it out. “Otherwise, you can clean the wick by soaking and rinsing it with cold water and removing any grime gently with your fingers.” Leasure warns against using any bleach or chemical cleaning solutions on the filter, as they can damage its antimicrobial coatings.

There will be obvious signs when your humidifier has reached the end of its useful lifespan. “Replace your humidifier when the housing is cracked, seals are failing, or the motor no longer works,” Shavers say. Also, if mold keeps returning after thorough cleaning, she notes that’s another sign. “Most humidifiers last five to ten years, depending on care, so if yours is aging and performance is declining, upgrading to a newer model is often the smarter long-term choice,” Shavers says.

There are many great humidifiers on the market. But to find the right one for you, it’s worth asking yourself some questions. Consider the size and placement. If you get a humidifier that sits on the floor, where will you place it? You don’t want to wake up in the middle of the night and knock it over on your way to the bathroom, or have to move it out of the way whenever you need to open your bedroom closet door. On the other hand, if you get a tabletop humidifier, will the mist stain your table? No matter what you’re looking for, we’ve tested dozens of humidifiers to help you find the right one for your lifestyle.