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For The IAQ Industry Mar, 2008 Vol. 1
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Air Filtration
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In most homes, particle levels are usually low enough not to be a health issue. However, in some cases particle levels can be problematic. This is particularly true if the occupants suffer from allergies or respiratory illness. To effectively filter the air it must be filtered continuously. In forced air heating systems this can easily be accomplished, and if the system is equipped with a multi-speed fan, then the lowest fan speed can be used to provide continuous circulation and filtration even if the system is not operating in a cooing or heating cycle.
If the house uses a heating system other an forced air and does not have a central ventilation system then it becomes very difficult to effectively filter the air. Stand alone filtration systems are available but are usually only capable of filtering the air in a small area .
Also, remember that forced air furnace filters are ineffective at removing health damaging particles from the air, they are intended to prevent large particles from accumulating on and around the fan and motor. Particles between 0.3 and 6 microns are the sizes that need to be captured as they are small enough to get through the body's defense mechanisms and enter the lungs.
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Getting Rid of VOCs
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Volatile Organic Compounds (V)Cs) are highly evaporative chemicals that off-gas in buildings from many different sources. It is widely accepted that VOC's can cause a variety of health problems. However, what can be done in buildings with high VOC readings? The two common solutions include removing those substances that are off-gassing, and dilute the chemicals with increased ventilation. Both work, but cannot always be easily accomplished.
Two other methods have been somewhat commonly used with mixed results. First is “bake-out”. This involves heating the dwelling for a period of time with high temperature, typically around 100 degrees. All the windows are then opened and the ventilation system is run at full capacity. This process is repeated for 2 or 3 days. This method supposedly causes the materials to release their chemicals quic ker rather than over a longer period of time. The second method often used utilizes ozone. Powerful ozone generators are run for a period of time in a closed dwelling. Again, after the process, windows and ventilation system operation remove the ozone and chemical byproducts. Both methods have their advocates and detractors. Positive and disappointing results have been realized using both methods.
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