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Air Purifiers

Indoor Air Cleaning & Filtration Technology

What Makes Air "Unhealthy"?

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.

Beyond The Hype - What You Need To Know

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.

Common Air Cleaning Systems

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.

Lesser-Known Air Cleaning Systems

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.

A Final Note On Air Filtration

nl48g3Through 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.

Is Air Quality Effecting Your Health?

Recently published studies have addressed the problem of Sick Building Syndrome (SBS) in many offices and schools. And it seems not a day goes by without some mention in the news about poor indoor air and it's health effects. Some of the same irritants and conditions that cause building-related illness in these environments could be lurking in your home. As you might remember, there are three main components to unhealthy indoor air: particulate matter (like dust mite allergen, dander and smoke), micro-organisms (like bacteria, mold, and viruses) and volatile organic compounds (like formaldehyde, ammonia, and fumes from solvents). According to the American College of Allergy, Asthma and Immunology, 50 percent of illnesses are either caused and/or aggravated by polluted indoor air. Symptoms that could accompany having a "sick" home, office or school include:


  • Aggravation of asthma
  • Cold or flu-like symptoms
  • Eye irritation
  • Fatigue
  • Fever
  • Headaches
  • Inability to concentrate
  • Lung infections
  • Nasal stuffiness
  • Rashes
  • Shortness of breath
  • Wheezing

Practical Tips For Improving Home Air Quality

The good news about your home's air quality is you can take action to improve it without having to spend a fortune. The main focus of this article is air filtration products that can fit any budget. First, here are a few inexpensive steps you can take right now to minimize your exposure to unhealthy home air.

  • Prohibit smoking indoors.
  • Use air conditioning, particularly during high-pollen seasons and on high-smog days. (Note: Overcooling your home on high-humidity days can cause condensation and possibly mold).
  • Eliminate other mold-causing moisture:
    • Vent your clothes dryer to the outside.
    • Make sure dehumidifiers and humidifiers are frequently cleaned and maintained.
    • Monitor and fix potential leaks and spills.
  • Maintain your HVAC system by changing or washing your filters when appropriate.
  • Don't store old containers of paint, solvents, pesticides or other household chemicals.
  • Keep lids tight on cleaning products and consider switching to non-toxic, chemical free cleaning solutions.
  • Vacuum frequently and, for best results, use a HEPA filtered vacuum cleaner.
  • For more helpful tips on indoor air quality, visit the EPA website.


Considerations When Choosing A Room Air Cleaner

As discussed in the first Indoor Air Cleaning article, there are a number of different air cleaning technologies being marketed. But it's HEPA filtration that doctors recommend most often for effective air cleaning. Therefore, the following information will deal primarily with room air cleaners that utilize HEPA filtration. National Allergy carries a number of these HEPA room air cleaners made by top companies like HunterHoneywell and Austin Air.

Once you know you're in the market for an air cleaner, the next step is to know the room size of the room where the air cleaner will be used. For example, the Austin HM400 is good for larger rooms up to 20 x 25 feet, while our Vapor-Eze Clean Air 5000 unit is rated for smaller rooms (or vehicles) up to 12 x 15 feet. Many of our customers also have sensitivities to various odors and chemicals such as formaldehyde, chloroform, disinfectants, kerosene, exhaust fumes and others. If you or a loved one is chemically sensitive, or if you live in an urban environment with pollutant dangers, then a HEPA machine with added filtration for volatile organic compounds (VOC's) is a wise idea. Austin Air Cleaners include a filter canister filled with granular activated carbon combined with zeolite to effectively filter many of these VOC's and odors. The Austin Air HealthMate Plus takes VOC filtration a step further by a impregnating the granular carbon with potassium iodide for maximum chemical and odor filtration for compounds like formaldehyde and ammonia.

When guiding people through a room air cleaner decision, our customer service representatives are most often asked about noise level, required maintenance, and where to put the machine. We will look at these factors, but remember that the most important feature of an air cleaner is its ability to effectively filter the air.

The Noise Factor
The American Lung Association and others recommend that air cleaners have a motor to circulate air back to the machine for cleaning. Because of this, some people find machines like HEPA air cleaners to be noisy. Most of our customers would probably say the extra noise is a small price to pay for the peace of knowing they are getting cleaner air. In fact, many people cannot sleep without their air cleaner running because of the comforting "white noise" it provides. However, being able to control the noise is an important feature as well. For this reason, most air cleaners on the market today have variable speeds. A solution that we recommend for the noise-sensitive is to run the air cleaner on high during the day, or when it will not be bothersome to anyone, then during the evening, set the cleaner to a low setting. A variable-speed machine will be quieter on its low setting, however it should never be completely off.

The Question Of Maintenance
Any air cleaner that utilizes a HEPA filter and carbon pre-filter technology will require filter changes. Many customers appreciate any feature that makes this maintenance easier. All Hunter units contain filter change indicators, as do several of the Honeywell machines. Under normal operating conditions, the carbon pre-filter on Honeywell and Hunter units should be changed about every 3 months, while the main HEPA filter should be changed every 1-3 years. If you fail to change the filters on schedule, the air cleaner will lose effectiveness and may eventually end up with motor damage. National Allergy sells all available replacement filters for the brands we distribute. While they are more expensive initially, a benefit of Austin Air Cleaners is a very low maintenance cost because pre-filters only need periodic vacuuming and the main HEPA and VOC filters can be replaced together every 4-5 years.

Air Flow & Placement
You will find that the majority of machines sold currently vent the clean air upward to enable the most effective air circulation and to avoid stirring up dirt and allergens by blowing air across the floor. Air cleaner manufacturers realize that it is impractical for most people to have their air cleaner in the middle of a room. Thus, machines like Hunter have front air intakes so they can be placed against a wall and still circulate air effectively. Other machines feature 360-degree air intake and are best placed 2 to 3 feet away from a wall. Because we believe airflow is such an important factor, we recommend using a unit powerful enough to circulate the air through its filters at least 6 times per hour in the room used. How much air a unit moves is one of our main litmus tests in evaluating whether or not to offer a particular air cleaner.

If you would like more information about finding the right air cleaners for your home, we've compiled information about room size, filtration technology, replacement parts and price on our Air Cleaners At A Glance chart.

Simple Whole House Filtration

nl49g3 (1)For most people, the best strategy for having safe air quality in the home involves a combination of technologies at two different levels - the individual rooms AND the whole house. A great way to get whole-house filtration, if your home has a forced-air (HVAC) system, is by using a high-efficiency furnace filter. Traditional furnace filters are fiberglass and do very little to remove allergens and other dangerous particles from the air. In fact, they have an efficiency rating of only 2% for those smaller particles as compared to the HEPA filtration efficiency of 99.97%. However, because furnace filters have to balance filtration with airflow through your ventilation system, thicker filtration media like HEPA does not work as a furnace filter. The airflow in your ventilation system is not powerful enough to move air through a HEPA filter without risking damage to your system.

Electrostatic filters are a good choice for HVAC systems because the filter media is negatively charged to attract allergens and other small particles something like a magnet would to metal shavings. Electrostatic filters are available as permanent washable filters or as quarterly disposable filters. Permanent electrostatic filters are a more economical choice in the long term and National Allergy's permanent filters have a lifetime warranty. However, their filtration is not as efficient as disposable filters and they need to be cleaned monthly in order to maintain their electrostatic properties.

There are several highly efficient disposable electrostatic furnace filters available, like the 3M Filtrete Ultra Allergen 1250, the Filtrete Micro Allergen 1000 , and the Filtrete Ultra Allergen Furnace Filter. Did you know that 10% of Americans surveyed by 3M and the American Lung Association admitted to having never changed their furnace filter? It can be easy to forget, but if you are considering using disposable filters, they must be changed quarterly in order to maintain their effectiveness against small particles.nl49g2Once filtered, the air still has to travel through the ductwork where it can pick up particulate matter. One economical way to add a bit more protection is to cover incoming air vents with our electrostatic Vent Filtration Kit. The easy-to-use kit is made of a high-grade polyester media that attracts many of the larger particles that may blow in from your ductwork. Vent filters work best in conjunction with a furnace filter and will not remove particles already in the room nor very small particles.

Back To School, Back To Allergies?

As you have read, indoor air quality can be managed in the home, but there are often allergy and asthma triggers lurking in environments outside of our homes as well. Here are some air-quality action points to consider as we approach fall. College-bound students should keep in mind that dorm or apartment rooms are small and often allergy-filled. We recommend a portable room air cleaner like the Honeywell QuietCare or the Austin Air HealthMate Jr. for cleaning a dorm or small apartment room. Many of these buildings are older and may not be well ventilated so they can harbor mold, chemical contaminants and of course, dust mites. So, along with a portable air cleaner consider sending some comfortable, low maintenance encasings like those made from our SofTEK2 fabric so your college student can rest (and study!) in allergen-free air.

Many elementary, middle and high schools have also discovered troubling indoor air quality issues. This year school openings have already been delayed in towns and cities from Washington to Ohio, mostly because of mold. In addition to mold, typical classroom allergens can include dust mites, chalk dust, animal dander from class pets and pollen. You might consider talking to school officials about the air quality safety of your local school. Some might be willing to place an air cleaner in your child's classroom or take other measures to prevent harmful air. Both your child and his or her classmates will benefit from the reduced exposure to airborne contaminants. We offer special pricing for local schools interested in purchasing quantities of air cleaners for their facilities. Here is a source for additional Healthy Classroom tips.

Poor air quality is a serious issue, but one that you can have some influence on by doing your homework and making smart choices. We encourage you to visit to a local allergist if you think you may have a "sick" home, school or workplace. They can help you identify what triggers you truly need to avoid and clean from your environment. It is always wise to consult with your doctor first about your specific condition, treatment options and other health concerns you may have. Our goal is to keep you informed and educated so, ultimately, you and your family can breathe better and find relief from allergy, asthma, and sinus symptoms.

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