Recirculating air inside the home can result in such a build-up of allergens, particles and pollutants that the level of pollution indoors is greater than that outdoors. One of the simplest ways to clean indoor air is with a filter, but attention must be given to choosing the correct filter for maximum efficiency. All air cleaners are given a MERV rating (minimum efficiency reporting value) from one to 16, which indicates the size of particles the filter is designed to remove. The air filters that often come with furnaces or air conditioners are usually one inch thick and made of fiberglass. These may help protect the appliance, but they do little or nothing to clean the air in the home. A pleated and/or electrostatically charged filter will be much more efficient. Pleating increases the surface area of the filter, while an electrostatic charge captures and holds small particles. Hybrid filters use both the mechanical and electrostatic processes.
Porous filters, often made of cellulose esters or Teflon, are more efficient than filters made of fibrous material. The pore structure is small and complex, with a porosity almost 50 percent less than fiber filters. Porous filters may also be electrostatically charged or combined with carbon filters to remove odors and gaseous pollutants.
Keep in mind that air circulation is as important as the filtration system. The air in a room should be changed at least four times an hour, and some systems are capable of changing it up to 10 times per hour! In general, you should buy an air cleaner with the highest MERV rating you can afford to enjoy the cleanest air possible.
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