We are surrounded by a myriad of choices when looking to buy an air purifier. How can we know which kind is the best air purifier? I want to look at just one type of filter here. I’m sure we have all heard of HEPA filters. Really, they are everywhere these days. We see them in vacuum cleaners, furnace filters, and, of course, air purifiers. How many of you understand what a HEPA filter is and how it works?
I’ll briefly describe what is it and how it works. I will also explain what it can remove and who will benefit from using it. Do you need to use a HEPA filter in Alliance? Let’s find out.
HEPA stands for High-Efficiency Particulate Arrestance. These are widely accepted as the best air filters. First created in the 1940s, they were originally used in the Manhattan Project to control radioactive dust. The US military and other government agencies still rely on HEPA filters when they need to have clean air. HEPA filters can remove 99.97% of particles larger than 0.3 microns in diameter. A micron is one millionth of a meter. We can see only to about 10 microns with our eyes. One hair on your head has a diameter of about 80 microns.
These smaller particles are invisible to our eyes and easy to inhale. HEPA filters remove these particles before we breathe them into our lungs. Today, any filter that is capable of meeting these standards can be labeled a HEPA filter. Be aware of imitators. There are many filters out there labeled HEPA-type or HEPA-like. These are not true HEPA filters. They are usually only 85 – 95% efficient. No where close to a true HEPA filter.
HEPA filters actually get more efficient the longer they are used (to a point of course.) How is this so? It is because of the way these filters are designed. They are made of randomly arranged fibers formed into a mat. Usually these fibers are made from fiberglass. The fibers have a diameter of.5 to 2 microns. The space between the fibers is much greater than 0.3 microns. Yet, even with these large holes only 3 out of 10,000 particles can get through.
These filters trap particles in three ways.
- Interception: This affects particles larger than 0.4 microns. The particle enters the filter, hits a fiber, and sticks to it.
- Impaction: This affects particles about 0.3 microns. The particle travels through the filter and can not follow the curving air flow around a fiber. It hits the fiber and gets stuck. this is very similar to interception.
- Diffusion: This is mainly for particles smaller than o.1 microns. These smallest particles are hit my air molecules causing them to travel erratically through the filter increasing the chance of them hitting a fiber.
HEPA filters are very good at removing particles from the air. They will also get rid of some biological organisms. They are not so hot at removing chemicals and odors. These filters remove the three main causes of allergies: pollen, dust, and dander.
One important thing for you to remember is that an Alliance HEPA filter can only clean the air that goes through it. You need to be sure that the purifier has a strong fan. Another problem air purifiers have is by-passing air. This is when air can go around the filter and leave the air purifier without being cleaned. This is a problem in lower quality machines. Be sure you get a high quality air purifier so you do not have this problem. Unfortunately, high quality usually means a higher price tag.
These filters are ideal for someone with allergies or asthma. They remove most things that make you sneeze and cough. These are usually also asthma triggers. I use one myself and will never be without one again. I find it highly effective at relieving my allergies. These are not going to work well for chemicals and odors. For this reason HEPA filters are often combined with an activated carbon filter. This combination works very well and will meet most of your needs.