To understand how HEPA air purifiers work, you have to have a good imagination, and at least a passable grip on physics.

Imagine particles floating through the air, all of different sizes. Sort of like how you can actually see dust particles when the sun bounces off them at the right angle. Now imagine a filter that doesn’t allow the larger particles through; only the tiniest. We’re talking particles so small that the human eye couldn’t hope to catch a glimpse of them. If a single sheet of this HEPA paper were placed in front of a fan that was constrained, such as in HEPA air purifiers, very little air would be able to pass through because of the tiny size of the holes. HEPA filter air purifiers made in such a way would need constant filter changes since the holes would be plugged quite rapidly. So, double the size of the sheed, and we’ll get twice the filter life and air flow. This only works to a degree, though, because you can only grow the sheet so large before it becomes completely impractical. Instead, HEPA air purifiers are built with these sheets folded back and forth on top of itself so that a very large surface area is presented to the airflow, and the HEPA air filteres are made far more efficient. This is very similar to how real-world HEPA filters are made in actual HEPA air purifiers. In some cases, there is as much as 40 square feet of filter material folded up in the HEPA section of a single filter. These sheets are constructed of either fiber, paper-like, or a polymer material, depending on the actual filter.

So you can see how HEPA air purifiers are capable of stopping bacteria, viruses, and mold spores, in addition to larger, more obvious items such as dust. For the most part, HEPA air filter purifiers can claim to be 99.97% efficient at removing the particles that are 0.3 microns from the air that passes through the HEPA air purifiers. The key word, though, is pass through. If the airflow doesn’t pass through the HEPA air purifieres, than it cannot be claimed. So, in essence, the claim of 99.97% is actually pretty inaccurate in those HEPA air purifiers that aren’t well designed, in which much of the airflow goes right around the HEPA air filters, and back into the room uncleaned. One series of HEPA air filters, the IQAir HealthPro series, is the only line that actually specifies that over 95% of air that enters their HEPA air purifiers goes through the actual HEPA filter.

Worth mentioning is the Blueair product line. The Blueair product line uses a different approach to HEPA. Not only do they provide a large surface area for air to pass through in their products, but they also have much larger openings in their filters, which are polymer based. This allows the Blueair to use a much smaller and less noisy fan and still achieve far more airflow. To compensate for this, these air purifiers use electrostatic brushes in the airflow just before the HEPA element. The result is that the pollution particles are charged electronically and end up getting stuck to the filter media, despite the larger passageway and increased air flow.

HEPA filter air purifiers are actually quite simple, in reality. A fan shoves airflow through a filter. As the same air passes back through the filter, it gets purer and purer. Therefore, the bigger the room, the bigger the product. Another approach, though, is more small air purifiers, which tend to work better. Think of a long, narrow room. If you put HEPA air purifiers at each end, the air only has to move half as far as if you were to put one larger purifier at one end, or even in the center. This results in cleaner air as not only does more air get treated, but the same air gets treated repeatedly, far more often than with just one of the HEPA air filters. Many times, the price is either comparable or better, and if a problem develops in one of your HEPA air filters, you only lose one and still have one small one in operation until you’re able to replace or repair the other.

The amount of activated carbon, as well as the type and other things with which it is blended, as well as how it is used in HEPA air purifiers depends largely on the model and brand of the HEPA air purifiers.

For example, the Austin Air HM400 uses 18 pounds (!) of granular activated carbon impregnated with zeolite. The zeolite enhances the chemical absorption qualities fo the activated carbon.

The Austin Air HM400 SuperBlend also contains 18 pounds of granular activated carbon, but it is impregnated not only with zeolite, but also potassium. This makes it effective at removing formaldehyde.

The Blueair 501 and 601 systems contain three integrated HEPA air filters. Unlike Austin Air, Blueair does not specify the weight of the carbon included. The optional SmokeStop filters have a lot more activated carbon than the standard filters that the unit comes with, though.

The V-5 Cell filter in the HealthPro Plus by IQAir has a five filtration chamber that includes a blend of activated carbon, as well as impregnated active alumina. This provides for enhanced absorption. Like Blueair, IQAir does not tell us the weight of the activated carbon that is in their HEPA air purifiers.

In most cases, pollens and pet dander are the main things that people are concerned about when buying HEPA air purifiers. Odor and chemical absorption are often less important, if they’re important to the consumer at all. Some, though, may be looking for a high degree of both. for those people it is best to look for high caliber HEPA air purifiers that offer outstanding odor, chemical, and particle removal. Volatile organic compounds, known as VOC’s, such as ozone, pets, tobacco, smog, and even cooking can be irritating or downright unhealthy for anyone, not just asthmatics and those with bad allergies.