• Use distilled or demineralized water. Tap water contains minerals that can create deposits inside your humidifier that promote bacterial growth. And, when released into the air, these minerals often appear as white dust on your furniture. You may also breathe in some minerals that are dispersed into the air. In addition, use demineralization cartridges or filters if recommended by the manufacturer.

• Change humidifier water often. Don't allow film or deposits to develop inside your humidifiers. Empty the tanks, dry the inside surfaces and refill with clean water every day if possible.

• Clean humidifiers every three days. Unplug the humidifier before you clean it. Remove any mineral deposits or film from the tank or other parts of the humidifier with a 3 percent hydrogen peroxide solution, which is available at pharmacies. Some manufacturers recommend using chlorine bleach or other disinfectants.

• Always rinse the tank after cleaning to keep harmful chemicals from becoming airborne — and then inhaled.

• Change humidifier filters regularly. If the humidifier has a filter, change it at least as often as the manufacturer recommends — and more often if it's dirty.

• Keep the area around humidifiers dry. If the area around a humidifier becomes damp or wet — including windows, carpeting, drapes or tablecloths — turn the humidifier down or reduce how frequently you use it.

• Prep humidifiers for storage. Drain and clean humidifiers before storing them. And then clean them again when you take them out of storage for use. Throw away all used cartridges, cassettes or filters.

• Follow instructions for central humidifiers. If you have a humidifier built into your central heating and cooling system, read the instruction manual or ask your heating and cooling specialist about proper maintenance.

• Consider replacing your humidifier each season. Over time, your humidifier can build up deposits that are difficult or impossible to remove and encourage growth of bacteria. Even if you plan to toss out your humidifier at the end of the season, it still needs frequent cleaning in the meantime.

To keep humidifiers free of harmful mold, fungi and bacteria, follow the guidelines recommended by the manufacturer.