An excerpt from the new, revised 2005 edition of Home Safe Home...

HUMIDITY

Humidity is about the amount of water vapor present in the air. It is not strictly speaking an air pollutant, but the amount of water vapor in the air can affect indoor air quality and pollution levels.

Relative humidity is the percentage of water vapor in the air compared to what the air can hold at that same temperature. Humidity varies from place to place, depending on local geographic and weather conditions, and varies according to conditions inside buildings.

The humidity scale is measured as a percentage on a scale 0 to 100. At 100%, water vapor fills 100% of the air and condensation occurs. At 0%, there is no water vapor present and the air would be extremely dry. Over 50% humidity is considered damp, so the most comfortable level is between 35% and 50%. Hygrometers, available at local hardware stores, can be used to measure humidity levels.

High relative humidity, over 50%, encourages biological agents--such as bacteria and viruses, house dust mites, and molds--to grow and be released into the air. If you have high humidity, you will notice condensation on windows or windowsills, and obvious mold growth or a mildew odor.

Low relative humidity does not affect indoor air pollution.

SAFE SOLUTIONS

To make your home comfortable and combat biological pollutants, you may need a machine that changes the humidity.

A dehumidifier REMOVES water vapor from the air.

A humidifier ADDS water vapor to the air.

A dehumidifier will help control both dust mites and mold. In order for dust mites to stay hydrated, they must absorb moisture from the air. When the relative humidity is below 50%, dust mites dry out. Once the dust mite produces their allergen, they settle into carpets and fabrics. Individuals come into contact with the allergen after an activity such as vacuuming, dusting, or making beds stirs up the area and cause the allergen to become air borne. The best way to control dust mites is to reduce their numbers by controlling conditions, rather than trying to remove the allergen from the air.

Molds are a living fungus that require very high relative humidity (over 70%) and a food source, so it is not surprising that humid climates are very moldy. Most mold spores can be filtered out with a HEPA filter, but an even better way to control it is to eliminate it entirely by reducing the humidity to a level in which it cannot grow.

Answering the following questions will give you the information you need to choose the dehumidifier that is right for you:

• Which rooms need to be dehumidified?

Each room in your home will require removing different amounts of water.

	Damp	Very Damp
Basement	50 pints	65 pints
Bathroom	30 pints	40 pints
Bedroom	25 pints	30 pints
Laundry Room	40 pints	50 pints
Living Room	25 pints	30 pints

With this information, find a dehumidifier rated to remove the appropriate amount of water.

• What are the dimensions of the area to be dehumidified (width, length and ceiling height)?
• What is the desired percentage of relative humidity (such as 40%) you wish to achieve?
• Do you have mold in this area?
• Do you use air conditioning in this area?

And here are some features to look for:

• the capacity in pints of water that the humidifier is capable of removing
• automatic defrost (freeze control). This ensures maximum moisture removal with no offtime for manual defrost. (not having this feature is like not having a frost free refrigerator)
• adjustable humidity control
• signal light to know when the humidifier operating
• auto shut off so that when the drain pan is full the humidifier will shut off
• threaded hose connection on the drain pan that allows for a hose to be attached and run a drain opening
• automatic reset, so that once the drain pan has been emptied the humidifier will start without pressing buttons etc
• adjustable humidistat (30 to 80%)
• deodorizing filter if required.

Humidifiers are used in homes to relieve the physical discomforts of dry nose, throat, lips, and skin, and are particularly helpful for those with sinus problems. The additional humidity also helps alleviate common nuisances brought on by the dryness of winter heating, such as static electricity, peeling wallpaper, and cracks in paint and furniture.

There are three types of humidifiers:

• Console humidifiers are encased in cabinets which are designed for floor use.
• Portable humidifiers are smaller and more readily moved.
• Central humidifiers are built into heating and air- conditioning systems, and humidify the whole house.

One problem with humidifiers is that they can pollute the air with microorganisms that grow in their moist environments. Studies by the EPA and the Consumer Product Safety Commission (CPSC) have shown that humidifiers can disperse microorganisms from their water tanks into indoor air, but they have not concluded that these dispersed material pose a serious health risk. This problem can be prevented with proper use, care and cleaning of your humidifier.

In addition to making your home more comfortable, adding moisture to the air can lower your heating bill. Since higher humidity make the air feel warmer than itês actual temperature, you can set your thermostat to a lower level and still feel the same warmth. Moist air also keeps your skin soft and smooth.

An excerpt from Home Safe Home by Debra Lynn Dadd.