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