Biological agents are found to some degree in every home, school and workplace. These biological sources include outdoor air and human occupants who shed viruses and bacteria and animals who shed allergens and indoor surfaces and water reservoirs where fungi and bacteria can grow. A common culprit are inexpensive humidifiers .A number of factors allow biological agents to grow and be released into the air. Especially important is high relative humidity which encourages house dust mites to increase and allows fungal growth[molds] on damp surfaces. The recommended level of humidity is 50% or under.

Dust Mites
Dust mites live 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%, dust mites dessicate [dry out].Their appetites increase as the relative humidity climbs. This is significant because their fecal material is the source of the dominant dust mite allergen.

Once produced, the allergens settle into carpets and fabrics. The dust mite population remains potent for approximately 9 months. Individuals come into contact with the allergen after some activity like vacuuming, dusting, or making beds has “stirred up” the area and cause the allergen to become air borne. For this reason air duct cleaning and air filtration devices are limited in combating dust mite allergen. Vigorous vacuum cleaning and use of acaricides can offer some short term reduction in dust mite allergen levels. According to studies conducted at Wright State University , dust mite infestations if the relative humidity is consistently maintained below 50%.

The survival rate of adult dust mites is limited to 4 to 11 days in relative humidities below 50%.Dust mites in the protonymph stage, however, can survive in this dormant larval stage for several months waiting for high humidity conditions to return.

Molds
Molds are a fungi. They only require high humidities [70% or higher] and an inorganic- based material on which to feed. It is no surprise they are plentiful in humid climates. Cooler surfaces create a perfect breeding are for mold because of the relative humidity next to them will be near saturation or the dewpoint. The surface may even be wet with condensation.

Individuals may react to the mold’s spores or to mytoxins [a toxoc gas] released by the mold. Unlike the dust mite allergen ,mold spores remain airborne for significant periods of time and are always present to some degree in the outdoor air. Most mold spores measure 5 to 10 microns in size and can be filtered out with the proper hepa media. Mold growth can be eliminated in the home through humidity control that maintains reduced relative humidity levels and prevents cooler surfaces from becoming damp.

Time to dry out
Although condensation on windows may not be a constant problem, excess moisture in the air is along term problem an therefore no humidifier will cure it in a few days. However, over a period of weeks you will notice that mold spots dry up and can easily be removed, damp patches will dry out, there will be no more mold on shoes, clothes or bedding.

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Features to look for in a Residential Dehumidifier

The capacity in pints of water that the humidifier is capable of removing. Make certain that the humidifier has automatic defrost[freeze control]. This ensues maximum moisture removal with no offtime for manual defrost. Compare this to not having a frost free refrigerator. Better humidifiers have:

1. Adjustable humidity control.
2. Auto signal light to know when the humidifier operating.
3. Auto shut off so that when the drain pan is full the humidifier will shut off.
4. Threaded hose connection on the drain pan. This allows for a hose to be simply attached and run a drain opening.
5. Automatic reset, so that once the drain pan has been emptied the humidifier will start without pressing buttons etc.
6. Adjustable humidistat [30 to 80%].
7. Deodorizing filter if required. A nice extra for a humidifier.