There are three classes of indoor contaminants: (1) microbial, (2) gases, and (3) particulates.
Filters deal only with large (course) particulates, or house dust. Although a manufacturer may claim that nearly 100% of particulates (usually .5 micron or larger) are removed from the air, we must remember two things.
- The air must pass through the filter in order to be filtered. Only about 20-25% of the air in the home actually circulates through duct system,
- Although nearly 100% of the course particulates are removed, 98.5% of the particulates in a home are to small to be filtered!
HEPA (High Efficiency Particulate Air filter) filters are very popular. In laboratory tests (not necessarily real world) they have a minimum efficiency of 99.97% on .3 micron particles. Remember this is only the air that passes through the filter, which is generally a one room filter. HEPA can make a significant positive impact, but they do not address the whole problem
The five key disadvantages of a HEPA filter are
(1) Frequent and costly replacement,
(2) Require powerful blower which is noisy and expensive to maintain,
(3) Can be breeding ground for bacteria, mold and fungus,
(4) Does not remove odors, gases, pesticides, viruses and many bacteria,
(5) Most of the particles are smaller than .3 micron, and too small to filter
Contact Della Powell directly for an IAQ Evaluation and Interview or information about quality air purification for your home or office