Understanding the various technologies used in air filtration machines


A variety of different technologies are used in the multitude of different air filtration machines on the market today. Below we hope to break down what each technology does, and why they are important to consider when choosing an air filter

How does a standard air filter cartridge work?

Common Circular Air Filter Cartridge
  1.  The image above depicts a common circular filter found in many machines. The first component in this case is a relatively simple mesh like material to catch large particles, such as dust.
  2.  The second layer is typically an activated carbon mixture. Carbon is effective at filtering out gases and odors as it chemically reacts with many carbon based chemicals, which then attach to the carbon in the filter. Activated carbon is simply carbon that has been reacted with oxygen to open up a multitude of pores between the carbon atoms, meaning there are many more spots for the harmful or odorous chemicals to attach and get stuck in the filter media.
  3.  The final layer in the above diagram, as in many air filters, is the High Efficiency Particulate Air (HEPA) filter. HEPA filtration was designed by the U.S. government to filter out radioactive particles, and as such is still the most effective means of removing very small particles from the air. To be classified as a certified HEPA filter, the filter must capture 99.97% of all 0.3 micron particles in the air that passes through it. This standard was chosen because particles that are 0.3 microns in size are the most difficult to capture. Larger particles are captured in the densely woven materials, and smaller particles are attracted by electromagnetic forces to the filter medium with enough force to be easily captured as well. The figure below illustrates these points.
HEPA Filter Diagram

Why are sealed machines are better?

  • Alternatively to circular filters, many filters utilize individual rectangular filter cartridges, as can be seen in the image below. Such machines also often have the advantage of being sealed versus unsealed. In a fully sealed machine all air that enters the machine passes through the filters. In unsealed machines a significant amount of air taken into the machine is just passed around the filters and out of the machine, left unfiltered for the time being.
Sealed, non-circular design, air filter machine

 

Zeolite

  • Another technology growing in popularity for its air filtration abilities is Zeolite. This naturally occurring, and now industrially synthesized, aluminium and silicone based substance has a crystalline structure with uniform sized pores throughout. After undergoing a few chemical processes the material begins to strongly attract and capture various gases and volatile organic compounds (VOCs) that are passed through its pores. Zeolite is used in conjunction with activated carbon in some filters.

 

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