Air Purifier Filters

An air purifying system is often only as effective as the filter that it uses. Your home’s heating and air conditioning system should be equipped with excellent filters that are regularly changed.

As in all areas of home construction materials, air filters have advanced technologically in recent years. Filters are made of foam, cotton, fiberglass or other synthetic materials. Some come enhanced with baking soda to help with odor prevention.

Filters are often effective at removing small particles in the air due to the small gaps in them, but not as effective at removing large particles that can settle on the ground or another surface before they make it to the filter. They come in many shapes, sizes and colors depending on their application. Those that are used with HVAC systems are often rectangular and flat. Other filters are pleated and circle-shaped, still others are very small, oval shapes to fit some air purifiers. Carbon filters are black while many HEPA filters are white.

Filter Terminology

Here, then, is a look at filters and the terminology around them:
Pre filter

  • Pleated filters work well because of their increased surface area to catch particles. These are great at getting dust and dirt out of the air. They are often called pre-filters because they are the exterior line of defense in air purification machines, acting as a first layer of filtration. They will capture large particles that can overwhelm finer filters deeper in the interior of an air purifier. Think of pleated filters as doing the heavy lifting before a HEPA filter (described below) does its second-level work. These filters look a lot like the filters in your automobile’s engine, only larger.
  • When installing filters, look for those with a high Minimum Efficiency Reporting Value (MERV), ranked from 1 to 20 (ultra-efficient). Make sure that your HVAC system can use a filter with a 15 MERV rating, for instance. Your HVAC system will need a powerful motor to effectively push air through a filter with a 15 MERV rating. It’s best to check the manufacturer’s recommended MERV ratings for new filters.
  • HEPA (High Efficiency Particulate Air) filters meet the highest federal standards for particle removal and were developed by the nuclear industry to keep radioactive dust off of people and surfaces. They are used in HVAC systems and many air purification machines. They differ from other filters because they will be advertised as removing 99.97% of all bad air particles, in contrast to standard filters that remove “only” 99% of such particles. HEPA filters are the gold standard of filters.
  • Carbon filters are very effective as well because charcoal has long been a great absorber of bad air particles and odors. The nooks and crannies in carbon materials make them ideal for trapping many air particles.
  • Booster filters are somewhat like pre-filters in that they are intended to enhance the effectiveness of a primary filter. They often come with baking soda embedded in them to fight odors.

You should note that the highest-rated air purifiers usually come with pre-filters on the exterior of the machine’s guts and HEPA filters working on the interior.

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