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When a shaft of light shines into your living room, you've most likely noticed the particles floating in its beam. If you're like most, you're probably not thrilled to realize your breathing those particles. And just what are they, anyway? There are three main components to unhealthy indoor air: particulate matter, micro-organisms and volatile organic compounds (or V.O.C.s). Common indoor particles include things like pollen, lint, smoke, house dust and animal dander. In fact, even homes that don't have pets probably still have dander in the air! It was recently published in the Journal of Allergy and Clinical Immunology that pet allergen is present in ALL homes, regardless of whether an animal is even present. Common airborne micro-organisms can include plant and mold spores, viruses and bacteria. Other indoor air pollutants include chemicals, gases and fumes like asbestos, carbon monoxide, formaldehyde, lead, nitrogen dioxide, as well as volatile organic compounds emitted from household cleaning products, furniture, smoke and cooking odors. While this extensive list of potential household air contaminants may seem daunting, there are filtration technologies available to help limit your exposure to harmful indoor air.
Companies promoting today's plethora of available air cleaning devices claim everything from filtration to the zapping and trapping of countless irritants ranging from house lint to the SARS virus. It is important to be an educated consumer as some companies' air cleaners do not serve your needs as well as others. A good first step is to know which airborne particles most concern you and your family. The best way to pinpoint your allergen triggers if you haven't already done so, is to be tested by an allergist. Then you can more effectively decide what type of machine will be best for you and your family.
A good air cleaner should be able to filter dust, pollen, pet dander and most other particles that fall within the 0.1-10 micron range. A micron is a unit of measure equal to one-millionth of a meter. Refer to the "Common Particle Size" chart below to see where different particles fall in the spectrum of filtration and to get an idea of what you can reasonably expect a filter to remove. To help give some perspective, a typical human hair measures about 70 microns in diameter - so even what is considered a rather large particle at 10 microns is still seven times smaller in diameter than a human hair!
Before we discuss specific air filtration technologies, here are a few other important terms you might want to know. A furnace filter or whole house filter is rated using a Minimum Efficiency Reporting Value (MERV), which measures the filter's ability to trap small particles. MERV ratings range from 0-12. You may also see test figures by an organization called ASHRAE (The American Society of Heating, Refrigerating and Air-Conditioning Engineers). This group performs testing on whole-house filters and publishes standards for ventilation for acceptable indoor air quality. An important component of room air purifiers is that it uses a motorized fan to circulate air thus bringing dirty air back to the machine for cleaning. Some terms used to describe a machine's ability to move air include Clean Air Delivery Rate (CADR) or Cubic Feet per Minute (CFM) of circulation. Many air cleaners are also given a Room Size rating, which is generally based on the length times width of the room. It is important to observe this Room Size rating as using an air cleaner in a larger room can limit its benefit. For more air quality definitions, visit this helpful "Air Cleaning Terms" page.
Electronic electrostatic machines are room air purifiers that use electronically charged collecting plates to attract particles found in the air. There are two general types of electrostatic room air purifiers, those that have motorized fans to circulate room air and those that don't. A recent article by a leading consumer magazine rated a motorized electronic electrostatic machine as its top air cleaner. That same test found several other electrostatic machines to be ineffective. Why? The latter machines did not circulate the air past the collecting plates. This is what the EPA has to say, "A very efficient collector with a low air-circulation rate will not be effective." Generally speaking, any electronic electrostatic machine will rapidly loose effectiveness as dust builds up on the plates. While you may save some money on replacement filter costs, we have found that electrostatic plates need to be cleaned as often as every week in order to maintain their effectiveness.
Another type of air cleaning system is utilized by ionic precipitators. These machines are usually small table-top units that "precipitate" or dispense ions into a room. The ions find and attach themselves to particles in the air. These newly formed particles maintain their charge and then "seek out" a charged surface and attach to it. Usually these surfaces are nearby walls or furniture that may need to be wiped down periodically because particles collect on them. National Allergy carries several ionic precipitators, including the Wein 2500 which we recommend for basement and crawlspace use, particularly for removing airborne mold and mildew. Chronic sinusitis sufferers especially enjoy the benefit of the reduced airborne mold and the often-accompanying musty smell.
The other major air cleaning systems involve moving air through a filter media. For example, electrostatic whole-house filters are very effective at turning your furnace into an air filter. When speaking of room air purifiers, most doctors recommend HEPA filtration media. HEPA filters were originally developed during World War II to prevent the discharge of radioactive particles from the exhaust of a nuclear reactor facility. They have since become a vital technology in industrial, medical, and military clean rooms and have grown in popularity for use in portable residential air cleaners. A true HEPA filter, by definition, must remove 99.97% of particles at least 0.3 microns in size - as small or smaller than pollen, pet dander, mold and some smoke and smog particles. Warning: Filters using less efficient filtering materials are frequently being referred to as "HEPA-type" filters, though their actual efficiency may be 55% or less for particles at 0.3 microns.
For the best protection from environmental pollutants like smoke, odors, smog and chemicals, some HEPA air cleaners have added activated carbon in either granulated or blanket form. Carbon, especially when paired with zeolite, is naturally formulated to remove cigarette or pet odors, paint fumes and other volatile organic compounds. A further technology that is helpful for the chemically sensitive is impregnating a carbon filter with potassium iodide, as in our Austin Air HealthMate Plus units. This technology provides filtration of additional chemicals like formaldehyde and ammonia. Please be aware that no air cleaner can completely protect against the dangers of second-hand smoke.
Recently, hospitals and other industries have been using installed ultraviolet filtration systems to combat dirty air and to arrest harmful viruses. UV technology involves passing air by a powerful ultraviolet bulb that is intended to alter the DNA of any harmful proteins or organisms, making them unable to reproduce. While the concept is viable, in order to be eliminated, an organism must be exposed to the UV for longer than the few seconds it takes for the airflow to quickly pass the particle past the bulb. This technology is currently being integrated into some different types of air cleaning machines, but is still considered developmental in its ability to act alone as an effective air cleaning method.
Ozone generators are also sold as another method of air cleaning. The EPA describes ozone this way,
"Ozone is a molecule composed of three atoms of oxygen. Two atoms of oxygen form the basic oxygen molecule--the oxygen we breathe that is essential to life. The third oxygen atom can detach from the ozone molecule, and re-attach to molecules of other substances, thereby altering their chemical composition. It is this ability to react with other substances that forms the basis of manufacturers' claims."
The American Lung Association has deemed most of these machines unsafe because ozone, in certain quantities, can trigger asthma attacks. In fact, "the U.S. EPA (1995) concluded that tabletop and room unit ozone generators are not effective in improving indoor air quality." (source: "Ozone Generators." American Lung Association.) Some UV and electrostatic machines may also produce ozone as a by-product. So if you are considering one of these types of air cleaners, be sure to find out whether the ozone output is considered safe.
Photo-catalytic oxidation (PCO) is a relatively new technology that converts toxic compounds, even carbon monoxide and nitrous oxide, into benign components such as carbon dioxide. The chemical process is fairly complicated, however to read a bit more about this technology, click here. PCO technology has a lot of potential for destroying low level pollutants like bacteria, viruses and fungi in indoor air. However, many air quality professionals feel that there are some technical issues that remain to be resolved before this technology is completely safe and effective for residential use. In addition, most of these units are very expensive and do not have strong air flow.
Through our years in business, National Allergy has earned the respect of thousands of physicians because we provide quality products and we care for the health of their patients. We have found that most doctors agree that the first line of defense against allergens is an allergy-proof bedroom. Air cleaners should only be used as one of several steps in creating a healthy home environment, particularly for those sensitive to dust mite allergen which is not often airborne for very long. Step one is to cover your mattress and pillows with mite-proof encasings. Reducing humidity and controlling mites and other allergens in your carpet or furniture are other key steps to keeping the environment in your bedroom and home clean. Air filtration works wonderfully in conjunction with these steps by removing airborne irritants that can cause discomfort. Countless customers have experienced relief from their allergy and asthma conditions by following this doctor-recommended, step-wise protocol.
We hope this article has been helpful for you. There is a lot to know and learn about the different air cleaning systems on the market today, so next month we will take a closer look at specific options available for room air purifiers and whole house filtration with the goal if helping you decide what may be best for you and your family.
This information is for educational purposes only. Always consult with your doctor first about your specific condition, treatment options and other health concerns you may have.