This is borrowed from Nature’s Home Filtration Facts, this is a great website that is full of information. If you would like to learn more about filtration and ways to improve yours, please go to http://4natureshome.com/index.html
Room Air Cleaning vs. Whole House Systems
Several major consumer publications and organizations offer consumers advice on the purchase of individual room air cleaners compared with whole-house systems. Basically, room air cleaners claim to clean one room and are portable devices which may or may not have the ability to move air. Whole-house systems are devices installed within a forced-air heating and/or cooling system, inside the existing ductwork. These systems range from a simple High Efficiency Particulate Air (HEPA) filter easily installed by the homeowner to contractor-installed germicidal and toxic gas light systems and humidification and/or dehumidification devices.
The recent popularity of individual room cleaners has been brought to the attention of several consumer advocate groups. One highly-advertised unit claims to be highly efficient at removing particulates from a room, and claims that customers are 100% satisfied with its quiet operation. A major consumer testing organization analyzed these claims and determined that, yes, customers were satisfied with the noise level because the unit had no fan or moving parts. However, when tested for efficiency (particulates, smoke, pet dander), the unit did not perform according to advertised claims. In a particularly twisted marketing campaign, this company has touted the weakest part of their product (the fact that it does not move air with a fan) as the most satisfactory aspect of their product.
Good Housekeeping goes even further and in their words: “Bottom line… save your money. You can’t rely on this product to clean the air in your home. Plus, any retail room air cleaner has limited efficiency and effectiveness as they are only designed to clean one room at a time.”
Filtration vs. Air Cleaning
There are a variety of furnace filters available with a wide range of prices and reported efficiencies. Many of these filters are supplied by the furnace manufacturer upon installation or are available at retail outlets. Called “MERV Ratings” (Minimum Efficiency Reporting Value), the higher the MERV number, the better the efficiency. These filters are designed to protect the furnace and do a fair to poor job at that and are mostly made of fiberglass or a pleated blend of woven material. When choosing a filter, it is important to take into consideration its efficiency rating, as well as how restrictive it is to air flow. Generally the more expensive the filter is, the more restrictive it is to air flow due to it being more dense for higher efficiency. Filters that restrict air flow, more than the design of your heating and cooling system can handle, will affect the furnace’s and air conditioner’s performance and efficiency and may cause damage to the system.
Nature’s Home products are designed to work in conjunction with your existing heating and air conditioning system. The high efficiency filters can be replaced easily by the homeowner. The whole-house systems are installed by professional heating and air conditioning contractors to convert your heating and cooling system into your whole-house air treatment center. The air in your home passes through this system several times an hour, unlike passive room cleaners. In order to effectively remove particulates, pollen, dander and smoke from the air, multiple passes through HEPA filters is required.
Stand-alone room air cleaners cannot possibly match the effectiveness and efficiency of whole-house systems. They simply do not move the large volume of air required to remove indoor air pollution. By using your existing forced-air system, you can have measurably cleaner indoor air.