What Makes Air Purifiers with HEPA Filters Work Better?
If you’ve been looking into the world of air purifiers, HVAC systems, and vacuums, you’ve probably heard the term HEPA before. But what exactly is a HEPA filter and what makes them better than standard air filters? Today’s article will walk you through the ins and outs of this subject.
What HEPA Is
HEPA stands for “high-efficiency particulate air.” In the United States, a filter is considered a HEPA filter if it is able to catch at least 99.97% of airborne particles with a size of 0.3 microns. This statistic can be a little confusing, but basically what it means is that HEPA filters have the most trouble catching 0.3 micron particles (which are very, very small, by the way), but they still catch the vast majority of them. Particles that are larger or smaller than 0.3 microns may be filtered with even more efficiency. In other words, HEPA filters are very good at what they do. In fact, HEPA filters are used in places like hospitals and nuclear facilities to keep the air as clean as possible.
Because of this high-quality standard and notoriety, however, there are many manufacturers that use tricky wording to make you think that you are getting a HEPA filter when the product does not actually meet that 99.97% efficiency rate. These companies will often use terms such as “HEPA-like” or “HEPA-type,” and while their products may still be good filters, able to trap 85-99% of particles, they do not meet the official definition of a HEPA filter.
How HEPA Filters Work
HEPA filters are made up of a web of crisscrossing and interconnecting fibers, typically either glass or synthetic materials.The gaps between these fibers are incredibly small and unevenly spaced, unobservable without the help of a powerful microscope.
There are three main ways these filters trap particles. The first happens to larger particles, or particles that are bigger than 1 micron. These are too big to fit between the fibers of the filter and so get stuck on impact in a process called straining.
The second is through something called interception, which is what happens to particles that are smaller than 1 micron but bigger than 0.3 microns. These materials are small enough to fit between the fibers, so you would think they’d be able to pass through the filter and out the other side. But the twisting and convoluted layout of the fibers means that a particle following the airflow through the filter can turn too fast or too slow and stick in the web.
The final way is called diffusion. This process happens to the particles that are less than 0.3 microns. They’re so small that the air molecules make them bounce around, moving in random patterns. This erratic movement causes them to eventually come into contact with the sides of the filter and get stuck.
These three processes combine to make HEPA filters the most efficient at collecting potential contaminants in the air.