Can Air Purifiers Really Remove Particles Smaller Than .1 Microns?

At aeris, we are committed to serving our customers with integrity and honesty. Unfortunately, not all companies follow the same high standards as we do. Recently, several air purification companies have claimed to be able to remove particles down to .003 microns, citing Brownian Motion as the reason. This is a much smaller size than the .1 microns that aeris purifiers are proven to be able to remove. While this may seem impressive, without recognized tests to prove these claims, what validity do they have?  Let’s take a closer look.

What is Brownian Motion?

In 1827, Scottish botanist, Robert Brown, observed that pollen grains move in random directions when placed in water.  Today, Brownian Motion is used to define the random zig-zag movement of small particles caused by collisions with other fast-moving particles.

While all the particles are constantly moving in Brownian Motion, they’re not all traveling at the same speed. Smaller particles absorb more momentum from collisions which makes them move much faster.

What does Brownian Motion have to do with air purifiers?

Imagine particles of different sizes flying around in the air inside of your house.  Each of these particles is measured in microns, which are one-millionth of a meter or 1/25,000th of an inch.

Some of the most common particles in homes are:

  • Dust Mite Debris: 0.5 to 50 microns
  • Household Dust: .05 to 100 microns
  • Human Hair: 70 to 100 microns
  • Spores from plants: 6 to 100 microns
  • Smoke: .01 to 1 microns

True HEPA air filters are 99.97% effective in capturing particles as small as 0.3 microns, which, as you can see, means that they should filter out all of the most common household pollutants.

But, what about smaller particles, like coronavirus?

Coronavirus particles are about .1 microns. That’s 30 times smaller than the United States Department of Energy’s (DOE) standard for what size particles HEPA filters should be able to trap. So, why would any air purifier company that uses HEPA filters claim to be able to filter out something that small?

That’s where Brownian motion comes in.

Think about those particles moving around in the air again. As air flows through the filter, the larger particles (larger than about 0.5 microns) are heavy enough that the airflow from the filter propels them forward into the fibers of the filter, where they get stuck.

But, the smaller particles, the ones under .3 microns, are so light that they don’t actually flow with the air.  In fact, if these tiny particles did fly straight, they would fit right through HEPA filters.

Instead, they bounce wildly off of other larger particles in the air in random patterns that send them careening off into different directions. It’s these zigzag patterns that cause them to hit the fibers of the HEPA filter and get stuck.

So, are the companies who claim that their purifiers can remove particles smaller than .3 microns telling the truth?

Perhaps, but that’s not the whole story…

We know that HEPA filters are excellent at filtering out particles larger than .3 microns and we also know that, because of Brownian Motion, particles smaller than .3 microns get trapped as well.  In fact, NASA recently conducted tests to prove that true HEPA filters can trap nanoparticles (particles smaller than .1 micron).

But, without having air purifiers tested against national and international standards, it’s impossible to even determine if the purifiers use True HEPA filters. Without outside testing, any claims that these other purifier companies are making are done from inferences, not facts.

That’s just not good enough for us. Any claims that we make at aeris are based on real data from third-party labs. We test our system to the extremely thorough EN1822 European testing standard, and the ISO18184 test protocol.

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