FM90 - Field Control® Fresh Mist Central System Humidifier

Freshmist 90
Owners Manual
Understanding Humidity

UNDERSTANDING HUMIDITY

Humidity can be puzzling. It cannot be seen, heard, touched, smelled or tasted. Many people do not understand what a humidifier will or will not do.

Probably the best way to judge whether the humidity is too high, too low or about right is to watch your windows. If they are heavily fogged you most likely have too much. If there is no moisture on them at all, especially in the corners, you have too little.

(NOTE: Moisture will not normally form on thermopane or when storm windows are used.)

If there is some moisture in the window corners and along the edges, the humidity is just about right. This is a good rule of thumb if you do not have an expensive piece of testing equipment. Your comfort is another good check.

TYPICAL QUESTIONS ASKED

  1. Why do moisture requirements vary from home to home?
    Requirements depend on the amount and dryness of air to be humidified. The larger and more loosely constructed the home, the greater the quantity of moisture required.
  2. How can I best check my home’s relative humidity?
    First give your humidifier time to build up the humidity to an acceptable level. Instruments are available to measure relative humidity, but from a practical standpoint, your comfort is the best guide. You cannot depend on table top or wall hung dial gauges.
  3. Should my humidifier be connected to softened water?
    You should use hard water in your humidifier. A humidifier can, under certain conditions be damaged by soft water. A popular misconception is that a water softener removes minerals. A water softener does not remove minerals but simply changes the mineral state.
  4. How long will it take my humidifier to build up the humidity in my home?
    Much depends on the outside temperature, time of year, home construction, and how dried out the home has become. In some cases, it may take a week or more.
  5. What are some of the common things that cause higher than average air leakage in the home, therefore causing low humidity?
    A. Jalousie windows
    B. Open fireplace dampers
    C. Cracks around windows and doors
    D. Open doors and windows
    E. Unusually large attic or foundation vents
    F. Range hoods and bath fans
  6. What else causes static shock besides low humidity?
    Some types of carpets tend to create more static than others. While the proper humidity level will reduce the static level, it may not eliminate static entirely.
  7. What is the safe humidity level for my home?
    In order to determine the safe relative humidity for homes exposed to various low outside temperatures, NESCA* conducted tests and published recommended humidity levels for various outdoor temperatures. These are shown in the chart. These levels help prevent damage to your home such as water running down the walls or even building up inside the walls. The safe indoor relative humidity percentage is not a fixed number but will increase or decrease as the outdoor temperatures rise or fall.
Outside Temperatures Maximum Safe Recommended Indoor Relative Humidity
-10° F 20%
   0° F 25%
 10° F 30%
 20° F 35%
 30° F 35%


*NESCA = National Environmental Systems Contractors Association.

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