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How Do Air Filters Work?

Air pollution is a massive problem in the modern world, and some studies have been able to establish a link between air pollution and cardiovascular and respiratory diseases. Now more than ever, it is imperative to invest in a good air filter.

There are particles in the air that are not visible to the human eye. Those particles can be dust, pollen, mold, animal dander, bacteria, aromatic compounds, etc. When these particles get into the body, they can cause irritation, flu symptoms and even allergic reactions. About 10,000 liters of oxygen enters the lungs daily, although the body only needs 420 liters. With so much excess air passing through our systems, it’s important to pay attention to the quality of that air.

A certain amount of household contaminants is unavoidable. Frequent cleaning can reduce these contaminants, but they will find their way in regardless. A good air filter can help grab the stragglers and prevent them from entering your family’s lungs.

For clarification: there is a difference between the air filter and air purifier. Air filters work by effectively trapping contaminants, while purifiers filter AND sanitize the air. Of course, no air filter or air purifier can eliminate 100% of the air pollutants in your home.

Usually, air filters are made from a spun fiberglass material, paper, or cloth. Air filters can trap and hold many different types of pollutants and particles, including:

Dust and dirt


Bacteria and microorganisms

Mold or Mold Spores

Fibers and lint

Metal, plaster or wood particles

Hair and animal dander

How do I make the right choice for my air filter?

Air filters are measured, on a scale from one to seventeen, by their Minimum Efficiency Reporting Value (MERV). Lower efficiency air filters can filter out bigger particles like dust and soot, but not smaller particles like bacteria and aromatic compounds. Higher MERV numbers indicate better filtration.

MERV 1-4: The cheapest and least effective filter. Good for macroscopic contaminants like small pieces of trash and dirt.

MERV 6-8: Made with pleated cloth or paper. Used for residential spaces.

MERV 9-12: More effective filtration for those with allergies, or who are sensitive to air contaminants.

MERV 13-16: Extremely effective. Used for very sensitive allergies or in healthcare applications.

Types of Air Filters

Disposable air filters: The vast majority of residential air filters are disposable. They’re cheaper to buy, easy to replace, and come in a variety of sizes and levels of filtration. Check out Filter King’s online store to find your ideal filter. We have just about every size you could ever need, with several different strengths and variations.

High-efficiency particulate (HEPA) air filter: One of the most reliable types of air filters available is the HEPA air filter. They absorb 99.97% of pollutants in the air smaller than 0.3 microns in size. This eliminates aromatic compounds, dust and bacteria. As such, HEPA air filters are not only used in homes but also in industries where the air is needed to be extremely hygienic. The medical industry is an example. Carbon air filters are also available to eliminate smoke from tobacco and other chemicals.

Washable or reusable filters are available in both flat-panel and pleated models and can be washed with water or vacuumed to eliminate any-particle build-up. They are more environmentally friendly than disposable filters. Better still, they can be cheaper in the long run. These air filters can last approximately five to ten years or more. Some filter companies claim that their reusable filters can outlast your HVAC system itself.

Pleated Air Filters: Pleated air filters use a special folding pattern to trap common household contaminants like dust and pet dander. Pleating allows for effective filtration without airflow restriction. This is extremely important, since an air filter is more effective when air passes through it more frequently. If there’s an airflow restriction, the air in your home is passing through the filter fewer times each hour, leaving it dirtier than it might be with a filter that has a lower MERV, but a higher frequency of air cycles.

Electrostatic Air Filters: Some air filters are deliberately charged electrostatically to trap smaller particles such as smoke, pollen or bacteria.

The Physics Behind Air Filters

All air filters work in roughly the same way. There are three main physical processes that allow air filters to grab small particles.

First is the idea of inertial impaction. Inertial impaction might sound complicated, but it’s just a fancy way to say “crash”. In inertial impaction, particles run into the strains in the filter, and stick. Air continues to move past the strands, and the particles are trapped in the filter.

The second process is called interception. Slightly more complicated than inertial impaction, interception, is the process of static electrical attraction. If a particularly small particle enters the filter, it may be so small that it won’t hit any fibers directly. In order to catch it, the fibers use static electricity to attract the particle to the fibers. This static electricity is the same thing that allows you to shock your sibling after scooting your socks on carpet.

The filter gathers charge in much the same way, with the air “scooting” past the fibers. Some filters, as we mentioned, are deliberately charged to maximize this effect.

The last process is the most complicated. It’s called diffusion, and it works in two ways. Both ways rely on Brownian motion, which, put simply, is the random motion of a particle within a fast moving fluid (like a dust particle in air). This Brownian motion, in the first method of diffusion, causes the particle to move around randomly within the filter media, eventually causing inertial impaction. The second method is a permanent state of Brownian motion within the filter - a kind of particle purgatory, with a given contaminant circling endlessly until you take the filter out of the vent.

Where do I get the best air filters?

Filter King is called the king for a reason. With unparalleled customer service, fast delivery, subscription flexibility, and one of the largest selections of filter sizes in the observable universe, Filter King is your go-to for air filter delivery.

Start by visiting our online store. Find your size, select your strength, and get your filter delivered in a few days!