| The A-B-C's of Air Filtration |
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By Dwight Barnett
Scripps Howard News Service Question: In your article on mold spores you did not say how to get rid of the mold or how to keep it out of the home. I'm worried about my children's health and how this might affect them. -- E-mail question Answer: According to the most recent research, indoor molds can be reduced by lowering the moisture levels inside the home and by cleaning or removing the mold spores that are visible. I have researched several air filtration systems that would be easy to install, use existing ductwork and would be reasonably priced. In my research I found several in-room air filtration devices that could be used in homes that do not have duct or fan systems. In-room models might be the choice for an older "drafty" home where the home has several whole house air exchanges per day. Newer homes, those built after 1978, have been sealed and insulated to the point where the air inside the home becomes stale and unhealthy. Typically a newer home has less than one whole house air exchange per day, which can lead to "sick building syndrome." A tightly sealed, energy efficient home or office complex is an ideal place for mold spores, germs, viruses, dust and volatile flue gases. According to the Asthma and Allergy Foundation (AAFA): "57 million Americans suffer some from allergies and asthma is America's most common illness; 17 million Americans suffer from severe asthma. Five million of them are children under the age of 18." A 1992 study by the Mayo Clinic of asthma cases diagnosed between 1964 and 1983 notes that indoor pollution, coupled with poor ventilation, was a probable cause in the doubling of asthma incidence among children. According to the American Lung Association, asthma incidence overall has jumped 61 percent since 1982. Newer homes need to have a ducted filtering system that not only filters the air, but also exchanges the inside air with the outside air in order to dump volatile gases, organic compounds and stale air to the outside. The unit should also be able to pre-heat the cold incoming outside air before filtering it to save on energy loss. The filter needs to be a true HEPA (high efficiency particulate air) filter in order to remove particles down to .3 microns in size (as a reference, a human hair is 150 microns). Although I have always been impressed with the large in-duct replacement filters such as AirBear, SpaceGuard, Aprilaire and RayDot, to date only the industrial sized Raydot is a true HEPA filter. A HEPA filter imposes a restriction to the airflow inside the ducts, which puts a strain on the fan and the heating/cooling units. Without proper airflow the furnace could overheat and be damaged or the cooling unit could lock up, damaging the compressor. What is needed is an additional fan to minimize the reduction of airflow through the filter. I did find several in-line HEPA filtering systems, but I found only one that not only has a built-in fan system, but also has a ventilation and heat recovery system. The GuardianPlus by Broan-NuTone is a new patented filtering system that filters 99.97 percent of the particulates in the air, reducing the levels of noxious gases, bacteria and germs. The system costs under $600 and can be installed in one day. With any filtration system the ductwork needs to be sealed at all joints and seams to prevent air loss or gain. In existing homes the ducts need to be cleaned and sealed prior to installation of any new system and should be done on existing filtering systems to lower dust and dirt, which will reduce energy costs. If you have a smaller, older home you might choose an in-room air purifier, although I still would recommend the whole house filtering system. Several choices of in-room air purifiers can be found at major discount and home stores or on the Internet. The smaller models cover an 8-foot by 7-foot room and larger units cover a 20-foot by 20-foot room. You can also shop the Internet for air purifiers and replacement filters. I would suggest you avoid any air purifier that uses water trays, wheels, wicks or any stored water to filter the air. Remember you are trying to lower the humidity in the air, not add to it. C. Dwight Barnett is a master inspector certified by the American Society of Home Inspectors. Questions may be addressed to him at P.O. Box 14091, Evansville, IN 47728, or e-mail him at dbarnett@evansville.net.)
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