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.

What type of water should I use in a humidifier?

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.

What is the ideal indoor humidity level?

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.

How important is my filter or wick?

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.