Friday, October 06, 2006

If You're HEPA and You Know It...

I got allergies.


--Betty Hill




Let me start by defining HEPA Filter. It stands for High Efficiency Particulate air filter. From what I can tell, the term "true HEPA" is used to refer to where the filter is placed in the unit in conjunction with the motor. This is more of a consideration for HEPA vaccuums (which have exhaust) as opposed to the stationary room filters. When something says it is a true HEPA, it is basically saying that its efficiency in removing certain contaminants from the air is 99.97% effective at removing particles that are .3 microns and larger in diameter.

What exactly is a micron? A micron is one millionth of a meter, but that probably isn't very helpful to you, so I'll put it another way. A grain of salt is approximately 60 microns in size. To give you an even better idea of how small this is, here is a list of airborne pathogens and their sizes. The items listed in blue are generally visible to the naked eye. Those in red are very difficult to see as individual particles. The smaller the diameter, the easier it is for the pathogen to get into our small airways and cause irritation.

  • Pollen 10-60 microns
  • Mold spores 1-60 microns
  • Lint 10-60 microns
  • Dust 1-60 microns
  • Bacteria .25-20 microns
  • Smog .05-20 microns
  • Tobacco Smoke .05-5 microns
  • Viruses .01-.1 microns

As you can probably infer by looking at the list above, HEPA filters--which can remove particles .3 microns in diameter and larger-- are most effective at removing almost all of the things in that list. With the exception of viruses, airborne pathogens of the greatest concern to CFers are easily filtered from the air with a HEPA filter.

What about ionizing filters?

Ionic air cleaners work by breaking up the contaminant and pushing it around the room in a different form. They split the offending molecule into separate positive and negative charges (ions). Ionizing units are great for removing odor, and many people like them because all you have to do is wipe of the metal plates inside the unit as opposed to changing out filters. However, when the airborne pathogen is merely ionized, the separated atoms, particularly oxygen atoms, have the potential to combine with one another and form what is called "ground level ozone."

Ground level ozone varies slightly from the stratospheric ozone that makes up the ozone layer surrounding the earth. Stratospheric ozone is "good" ozone; ground level ozone is "bad" ozone. "Bad" ozone (i.e. ground level ozone) has been shown to impair lung function. Naturally, anything that reduces lung function is something a CFer should avoid. The technology is coming along to make ionizing air purifiers better, but as a CFer I would urge other CFers to steer clear of them.

What about units (like the one I have) with an optional ionizing function?

My general though is that, yes, this is okay. If you need to deal with a strong contaminant that may have a particularly problematic odor, I recommend using the ionizing function while you are not in the same room where it's being used. Or, if you'd rather not even take a chance with the ionizer, spray some Neutra-air or Febreeze into the room and let the air filter run full blast for awhile.

Many people are attracted to air purifying units (like the Ionic Breeze or the Living Air Purifier) that do not have filters that need to be replaced. Although the idea of less maintenance and less expense is nice, I strongly recommend biting the bullet and getting a unit with filters that can be replaced. Yes, it's an added expense, but I think it's a worthwhile one. My reasoning on that is based on my understanding of mold spores. If you have a unit that has been sucking up mold spores but you never physically remove them from your home, you are only perpetuating the problem. Mold spores can lie dormant for long periods of time and can flare up again when just the right conditions are in place. If you are sensitive to molds (perhaps if you have ABPA) this can be a problem. I'd much rather buy replacement air filters than spend large portions of my paycheck on expensive anti-fungal medications like Vfend and itriconozole.

People with allergies and CF should look into HEPA filter systems. My personal and professional choice for an air filter is the Bionaire HEPA Tower. It is very efficient; the price is great; it's far and away the quietest air filter I've found for its size. My favorite features are that it oscillates (which means it is able to do an even better job of moving the air) and it has a remote control.

SEARS has two different sizes of the Bionaire HEPA tower. They both have an independent ionization function, which, for the most part I leave turned off. The only time I had the ionizer switched on was when we first moved into our new house and the air conditioner wasn't installed yet. Since our windows were open a lot of the time for ventilation, I ran the filter with the ionizer on (while I was out of the room) to break down the emissions from passing cars (we live on a busy street.

I am exceptionally pleased with the Bionaire product. I have researched air filters and purifiers for a number of years now, and this one has the technology and aesthetics that I deem acceptable. I hope that has been helpful. If anyone else has other questions about how to effectively keep their home as allergen free as possible, please let me know and I'd be happy to help.

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