Humidifiers can provide relief from the annoying effects of dry winter air, such as dry skin and chapped lips. Humidifiers may also be soothing for people who have asthma flare-ups because of dry indoor air. But whatever the reason for using humidifiers, it's essential to properly maintain and clean them. Dirty humidifiers can create more problems than they solve.

To keep portable or desktop humidifiers free of harmful mold, fungi and bacteria, be sure to follow the guidelines recommended by the manufacturer. These tips for portable humidifiers can also help:

• Fill humidifiers with distilled or demineralized water. Tap water contains minerals that can create bacteria-friendly deposits on the humidifier. 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 every day. 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.
• Clean humidifiers every three days. Unplug the humidifier before you clean it. Remove any scale, 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. Check your humidifier's instructions. Always rinse the tank after cleaning to keep harmful chemicals from becoming airborne — and then inhaled. Even if you plan to toss out your humidifier at the end of the dry winter season, it still needs frequent cleaning in the meantime.
• 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.
• Check humidifier humidity settings. Be sure your humidifier's humidity level is set between 30 percent and 50 percent. Humidity higher than 50 percent can promote the growth of dust mites, mold, fungi and bacteria. Some humidifiers have a built-in humidistat that shows the humidity level. If yours doesn't, consider buying a hygrometer to measure the humidity level. Hygrometers are typically available at hardware stores.
• Keep the area around humidifiers dry. If the area around a humidifier becomes damp or wet — including windows, carpeting, drapes or table cloths — 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.

If you have a console humidifier — one that's built into a cabinet — follow the manufacturer's instructions for cleaning and maintenance. If you have a central humidifier — one that's built into your central heating and cooling system — ask your heating and cooling specialist about proper maintenance.

Keep extra supplies on hand if your system requires disposable filters or special sanitizing solutions. If the humidifier contains a tank, keep the water clean. Finally, be sure to have console or central humidifiers inspected regularly.