Saturday, June 28, 2008

What are good air filtration devices for my health?

Removing allergens and irritants from the air you breathe is an excellent theoretical idea. It would be healthy for you only breathe in 79% nitrogen and 21% oxygen because there are many things in normal air that can cause disease in humans. For example, there may be allergens, like pollen, mold, animal dander, dust mite feces, very small airborne particles of carbon exhausts (PPM2.5), noxious gases like ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide, or other chemicals, viruses, and bacteria. Notice that there are 2 groups of substances in normal air: gases and particles.

In practice, though, there are several factors to consider. Air must be filtered to remove particles by pumping the air through a filter with small pores. These pores are too small to allow the particles through, thus removing them from the air. If the pores are small enough, then all allergens and airborne carbon particles can be removed from the air. The U.S. government has set rigid criteria for describing the filters. HEPA means high efficiency particulate air filter and it means that 99.97% of particles 0.3 microns or greater will be removed. All allergens are in the 20 to 50 microns range, so they would all be removed by HEPA filters. Organic compounds can be removed by passing the air through activated carbon. This does not remove other smaller gases, such as nitrogen dioxide or ozone. I usually do not recommend patients spend money to buy a filter using activated carbon.

I strongly recommend NOT purchasing any device called an ozone generator to clean air. They produce ozone which first of all does not clean the air. Second, ozone is a known trigger of respiratory and heart symptoms. Exposure to ozone is bad, that's why the U.S. government issues alerts on high ozone days and advises people to stay inside with the a/c on. Go to to find your local ozone count or click on the second link in my favorite websites in the top left hand corner of this website.

When buying an air filtration device, remember it only works when it is turned on, which uses electricity, and adds to the true cost. The filters must be changed routinely as directed, because the pores will get plugged up. Include the cost of the filters in your calculations about which device to buy. Choose an air filter that is big enough to produce at least 5 full exchanges of the volume of the room per hour. Otherwise, the air filtration device will not be big enough to have much effect filtering the room's air. Often, people buy a device that is too small for the volume of the room in which they want to have the air filtered. HEPA is the label one should look for when purchasing an air filtration device for your home or office.

Where can the devices be seen and purchased? I have seen HEPA filters sold in department stores [such as , , Target, Walmart], appliance stores [Best Buy], and home-improvement stores [such as Ace Hardware, Home Depot, Lowe's]. In my experience, there is no brand that is superior. Remember HEPA is a government-defined standard. Compare prices closely. The costs can begin at greater than $50 for the smallest HEPA device for say a small bedroom without the cost of the air filters or electricity considered yet. If you really know what you want, then don't forget to search the Internet. That's how I bought my HEPA vacuum sweeper for a very good price, after I did my research.

If you have questions about air filtration devices, ask your doctor or read more at This is an excellent summary article.

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