Dehumidification
Dehumidification
The Key to Comfort and Indoor Air Quality
Beyond Air Conditioning
A conventional air conditioning system is not designed to control humidity below 50 percent on a continuous basis. Air conditioners are actually air coolers. Warm air is passed across cooled refrigeration coils that absorb heat from the air and pump it outside. This leaves the air cooler. When moisture condenses on these cooling coils, extra heat is released. It is not surprising that new high effiiciency air conditioners try to reduce the amount of moisture removal. This is accomplished by doing less cooling to a larger volume of air to avoid condensation on the coils. Air conditioning is controlled by a thermostat that reacts to a demand for cooling. If it is 72 degrees outside and raining, there is not a need for cooling, but there is a need for dehumidification.
Dust mites and mold are the two most common allergens present in higher humidity climates.
Dust miteslive in upholstered furniture, carpets and mattresses. They feed on shed human and animal skin scale. In order to stay hydrated, dust mites must absorb their moisture needs from the air. If the relative humidity is below 50 percent, dust mites desiccate (dry out). Their appetites increase as the relative humidity climbs. This is significant because their fecal material is the source of the dominant duct mite allergen.
Once produced, the allergens settle into fabrics and carpet. The dust mite allergen remains potent for approxomately nine months. Individuals come into contact with teh allergen after some activity like vacuuming, dusting or making beds has "stirred-up" the area and caused the allergen to become airborne. Due to its size and shape, the allergen remains airborne for only a short period of time. For this reason, air duct cleaning and air filtration devices are ineffective methods of combating the dust mite allergen. Vigorous vacuum cleaning and use of acaricides can offer some short-term reduction in allergen levels.
According to studies conducted at Wright State University, dust mite infestations will be eliminated if the relative humidity is consistently maintained below 50 percent.
Molds are a fungi.They only require high humidity (70 percent or higher) and an organic-based material on which to feed. Iy is no surprise that they are plentiful in humid climates. Cooler surfaces create a perfect breeding area for mold because the relative humidity next to them will be near saturation or the dew point. The surface may even be wet with condensation.
The most common molds are the speciaes Alternaria, Epicoccum, Penicillium and Cladosporium. Individuals may react to the mold's spores or to mycotoxins (a toxic gas) released by the mold. Unlike the dust mite allergen, mold spores remain airborne for significant periods of time and are always present, to som edegree, in outdoor air. Most mold spores measure 5 to 10 microns in size and can fe filtered out of the air with proper efficiency filter media.