Disadvantages: Humidifiers are not easy to use. All units, portable as well as those installed in central heating systems, must be cleaned rigorously. Otherwise, they tend to become contaminated with mold and bacterial growth that may be blown through the house.
You should clean portable units every two weeks and central units once a month. Remove any residue, then let a solution of chlorine bleach sit in the basin for 30 minutes to kill any fungus or bacterial growth.
Ultrasound humidifiers tend to leave a fine white dust about your rooms, as the tiny droplets they dispense evaporate and leave behind calcium carbonate and other minerals present in the water. This may be prevented by using distilled (not de-ionized) water in the humidifier. Distilled water, however, is fairly expensive.
- The air in your home should range from 30 to 55 percent humidity.
- If the humidity is too high, mold and dust mites may thrive. Both are common causes of allergies. Mold also causes an unpleasant smell and can discolor surfaces.
If the humidity falls too low, on the other hand, the people in your home may suffer dry eyes and may develop throat and sinus irritations. The simplest way to measure humidity is with a gauge called a humidistat. These gauges are often packaged with thermometers. You can usually buy one in a hardware store for less than $10.
Source: Pure Matters