Types of Air Filters
Flat, pleated and HEPA
There are a number of different filter types used in air purifiers. The type of filter used is perhaps the most important factor in the unit's efficiency. That is, some filter designs are better at trapping particles than others. For example, pleated filters tend to be better than flat filters, and HEPA filters are generally considered the best.
Pleated filters are dense filters made of small fibers and pleated material. These two aspects of design and manufacturing play off of each other – the pleating increases surface area so that there is more filter for the air to pass through, while the density traps more particles. Together, these features heighten the filter's efficiency.
Flat filters , also called “panel filters,” are made with a standard fiber material such as wood fill or a synthetic. This material can be dry, but it is most often coated with a thin layer of oil that aids in collecting particles. Flat filters are generally classified as low efficiency.
High Efficiency Particulate Air (HEPA) filters are designed for maximum efficiency and made of tiny glass fibers. Technically, HEPA refers to the design, rather than the filter type. However, HEPA filters must meet very specific requirements to earn the name:
- A HEPA filter must remove 99.97 percent of all particles and allow no more than 3 particles (of 0.3 microns in diameter or more) out of 10,000 to pass through the filter.
Some filters are branded as “HEPA type” filters. There is no standard for what makes a filter “HEPA type”; the name merely capitalizes on the association, and some of these filters can have an efficiency of less than 60 percent.
Many people are concerned about their indoor air because of dust particles, pet dander, mold and pollen. Most filters are capable of removing the majority of these particles from the air, making it easier for you to breathe in your home. Furthermore, with proper air purifier maintenance, some filters only need to be replaced about every 5 years.