HEPA Air Purifiers Info

What are Hepa Air Purifiers?  Obviously it’s a device that filters air, but what exactly does HEPA mean? HEPA stands for High Efficiency Particulate Arresting. These filters have been around for quite a while, though they’re only more recently seeing public use. Way back in the ’50’s, the United States government, or more specifically the Atomic Energy Commission had a need for something to remove the tiny radioactive particulates that are created in the process of creating atomic energy. Since that time, HEPA filter air purifiers have been using HEPA technology to clean the indoors in various situations, from beauty parlors to clean rooms. Allery and asthma doctors use HEPA air filters to help alleviate sufferers of allergies and asthma. But how does HEPA work, exactly?

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.

1 Comment »

When picturing HEPA materials, you’re probably picturing something similar to an imaginary colander or screen. The materials in HEPA air purifiers actually do not look anything like that. Instead, they look like a very thin bail of fiberes, creating a veritible maze that the air has to find a route through, particle by particle. There are three different ways that HEPA filter air purifiers stop particulates. The easiest to understand is that a particle basically runs into a fiber and sticks. the second way is the particle getting within one diameter of a fiber in HEPA Air Purifiers and getting stuck on the fiber as it tries to skid by. Lastly, and the most complicated, is when very, very small particles (we’re talking 0.1 micron) travel in the gas flow, they sort of jump and juke due to the collisions with other molecules. This is called Brownian motion, and in itself can cause the molecules to be even more susceptible to the first two methods. To understand Brownian motion, picture bumper cars ramming into each other completely at random. Now picture the edges of the bumper car ring are actually sticky, or magnetic, holding the bumper cars to them. Now, to make things far more complicated, we’ll basically put edges all over the place so that the bumper cars have to navigate a treacherous maze. Only the other idiot bumper car drivers are still ramming each other, causing each other to get stuck, even if they would’ve skid through scot-free.

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.

2 Comments »

As good as HEPA air purifiers sound, they cannot remove gasses, chemicals, or odors. Consider that these are molecular level substances, and that the 0.3 micron holes are actually quite large compared to gas molecules. To compensate for this, most HepA air purifiers have some type of activated carbon based material that will absorb chemicals and odors. There are a number of different varieties of activated carbon that is included in most HEPA air filters. For example, the Air-O-Swiss unit has a thin mat in it to cancel out smells. In the Austin Air Purifier, there are pounds of activated carbon that do the same job. Regardless of the form, the carbon absorbs the gasses that would otherwise not be caught by HEPA air filters. These chemicals usually either cause unpleasant odors, or are possibly dangerous, harmful gasses.

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.

2 Comments »