Air Filter Q & A - Does an Air Filter Really Work?

Consumer is skeptical if air filters will help allergies.

by David Barnaby, AllergyBuyersClub.com Staff

From: Greg B. (Last Name and Email Address have been withheld)
Subject: Air Filter Question

I've been doing some research on air filters to find out which ones really actually work. By use of a particle counter that counts particles down to .3 microns I've discovered that very few filters (including hepa as well as electrostatic type which run a high voltage across metal plates) actually do much. This leads to my question....if pollen can be in the range of say 5-100 microns, when particles get SMALL enough are they no longer a concern for allergy sufferers? Is looking to filter particles down to .3 microns really helping or as it good enough to filter down to say 5 microns and not worry about the smaller stuff?

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To give you an example, the particle counter showed the air in my room had about 45,000 particles. The air coming directly out of my electrostatic air filter had about 35,000 particles. It's doing something but if the smaller particles are also contributing to my allergies my air filter isn't doing be much good! I've found similar results with a variety of "True HEPA" filters I've tested. Are all these filters completely useless or am I looking too deeply into this?

Any information you could provide is GREATLY appreciated.

Sincerely,
Greg B

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From: David Barnaby - Allergy Buyers Club
Subject: FW: Air Filter Question

Dear Greg,

In reality, it is the smaller particulates too small for you to see that we are most concerned with when cleaning the air for particulate removal. The particulates ranging in size from 2 microns in size down to 0.3 microns will remain suspended in the air the longest periods of time increasing the chance of your inhaling it. Also, this size particulate has the best chance of making its way through your sinus cavities and into your lungs than a larger size particulate. In addition, it is of the right size to not be easily exhaled out of your lungs as a particle smaller than 0.3 microns would. Therefore, an effective Hepa air cleaner becomes the utmost important combatant to these particle sizes.

The problem becomes more puzzling when you start rating the various hepa air cleaners on the market. The problem is that a hepa filter if placed in a testing lab will successfully remove 99.97% of all particulates 0.3 microns or larger but this is because the testing lab is an air tight environment where the particles have nowhere to go but into the filter.

In a real life setting, the efficiency will vary widely depending on how air tight the seal is between the filter and its housing. The design of the air cleaner and the way the filters are housed can affect the actual efficiencies of particulate removal by as much as 40 to 50 percent. That is why you got such wide swings in your measurements with your particle counter.

When we look at an air cleaner like our five star rated IQAir HealthPro unit we see a true Hepa machine efficiency as opposed to just a filter efficiency. This unit will remove at least 99.97% off all the particulates down to 0.3 of a micron or larger. But the IQAIR HealthPro unit takes it a step further. Since it is air tight, they were able to have an independent Swiss laboratory test their machine on particulates smaller than 0.3 of a micron. This is very important when you realize that 90% of all particulates in the air are 0.3 of a micron and smaller. Also, just because the smaller particles sizes have a better chance of being exhaled from your lungs does not mean all of them will. Furthermore, you must realize these super small particulates will remain suspended in the air for hours and will most likely be inhaled and make their way into your lungs because of their microscopic size.

This test is called the EN (European Norm) 1822 test. The way they conducted the test was done in two parts. They first determined the particle size that had the highest probability of making their way through the filter and back into the room. This is called the MPPS which stands for the maximum penetrating particle size. They determined that if they could determine this size and then conduct the second part to the test which is bombarding the filter with these size particles the efficiency measured would be an accurate measurement of the worst case scenario for this machine's performance. It was determined that any size particle smaller or larger than this MPPS particle size would have a higher efficiency. Keep in mind, that this test could only be conducted if the air cleaner was airtight so this cannot be done on any other air cleaners that we know of.

On the IQAir HealthPro it was determined that the maximum penetrating particle size was 0.2 of a micron for speed setting 3 and 0.16 of a micron for speed setting 6. The machine efficiencies for speed 3 was 99.95% and for speed 6 was 99.5% when they were tested with these particle sizes. Therefore, we can comfortably conclude that the IQAir HealthPro will be at least 99.95% efficient for particles smaller than 0.3 of a micron on speed 3 and 99.5% on speed 6.

These findings will reinforce the reasons we give the IQAIR HealthPro a 5 star rating and we feel it is the best air cleaner we have to offer.

I hope this may have cleared up any questions you had pertaining to particle sizes and air cleaner efficiencies.

If you have any questions concerning any of this please feel free to call or correspond.

Thank you,

Dave Barnaby

See all the air purifiers at Allergybuyersclub.com

First Published: Memorial Day, 2002
Updated: April 2007

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