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Air Purifier Buying Guide

Common Household Air Pollutants

Different air purifiers target different pollutants, so it's important to identify the pollutants you want to eliminate from your home before you buy an air purifier.

• Airborne Particles include pet allergen, dust mite allergen, pollen, plant spores, fungi, mold, and tobacco smoke, and they are the most common cause of indoor allergy and asthma attacks. A HEPA air purifier is the best method of eliminating airborne allergens. Here's a look at the average particle size of some common indoor airborne particles:

• Household Odors and Gases include cooking odors, kitty litter, tobacco smoke, various toxins, and gaseous pollutants like indoor pesticides or aerosols. Activated carbon filters are ideal for adsorbing gases and odors that are too small to be trapped by a HEPA filter. "Adsorb" is not a typo; "adsorption" occurs when materials attach through a chemical reaction.
   
• Volatile Organic Compounds (VOCs) are found in a wide variety of common household products: paints, varnishes, cleaning supplies, disinfectants, glues and adhesives, and even new carpet and building supplies. Look for ingredients like benzene, chloride, formaldehyde, ethylene, and toluene. VOCs can cause the following symptoms: irritation of the eyes, nose, and throat, headaches, nausea, and even severe chronic health conditions such as damage to the nervous system. The presence of VOCs can also exacerbate asthma.
   
• Microorganisms include antigens, pathogens, bacteria, and viruses. They're the everyday germs that make us sick. Mold is also considered a microorganism.

Air Purifier Filter Types

• HEPA (High Efficiency Particulate Air) Filters set the standard for air purification. By definition, a HEPA filter removes at least 99.97% of all particles as small as 0.3 microns. HEPA air purifiers were originally developed by the Atomic Energy Commission to capture radioactive dust particles. HEPA filters allow only very small particles to pass through them. Allergens such as pollen, animal dander, mold spores, and dust get trapped in the filter. The main disadvantage of the HEPA air purifier is that you have to periodically change the filter. The main advantage: If it's HEPA certified, then you know it works well. Not all HEPA filters are created equal. Size matters: the more square feet of HEPA filter, the more particulates it will be able to remove. The size, material, and construction of the actual filter media all play a role in the air purifier's performance and may account for why one HEPA filter is more expensive than another.

 
• Ion Generators and Ozone Generators create charged particles (ions) and emit them into the surrounding air. These ions combine with impurities (like dust) in the air, forcing the impurities to cling to a nearby surface. Consequently, ion generators often produce dirty spots on nearby walls and floors because they do not eliminate impurities; ion generators simply force impurities to cling to a surface (in the same way that static electricity can make a sock cling to a shirt). Ion generators are the second most popular type of air purifiers, but you won't find any ion generators or ozone generators for sale at achooallergy.com—because ion generators and ozone generators both emit ozone, a powerful lung irritant that is especially dangerous for people with asthma and other chronic lung diseases, children, and the elderly.
  
  
• Electrostatic Precipitators work on the same principle of electricity as ion generators and ozone generators, but electrostatic precipitators capture impurities rather than simply forcing them to cling to an external surface. Electrostatic precipitators, such as the Friedrich C90B Electrostatic Air Purifier, use electronic cells to charge particles within the purifier and immediately trap the impurities on collector plates. The main advantage with this type of air purifier is that the collector plates never have to be replaced; they can be easily washed in the dishwasher. Be aware that some electrostatic precipitators also generate ozone.
  
 

• Charged Media Filters work the same way as electrostatic precipitators, but they collect particles on fiber filters instead of plates. The advantage of these filters is that they are able to collect very small particles, sometimes as small as 0.1 microns, through a combination of a filter and an electrostatic charge. The disadvantage is that, like the electrostatic precipitator filters, charged media filters lose their efficiency fairly quickly, and they can require more frequent filter replacements compared to a HEPA air purifier. These types of units can produce ozone, but the better ones on the market do not. If you are going to purchase this type of air purifier, make sure that it does not produce ozone. The best air purifier in this category is the Blueair air purifier.



• Activated Carbon Filters are rarely used alone to purify the air, but they are often used in conjunction with other filters. Activated carbon and charcoal filters excel at adsorbing odors and gases and neutralizing smoke, chemicals, and fumes. "Adsorb" is not a typo; "adsorption" occurs when materials attach through chemical attraction. Activated carbon has been treated with oxygen, opening up millions of pores in the carbon. There are so many of these tiny pores that one pound of activated carbon has a surface area of 60 to 150 acres. This huge surface area makes it ideal for adsorbing gases and odors. These chemicals and gases are too small to be trapped by a HEPA filter, but they bond to the enormous surface area in the activated carbon. The bigger the carbon filter, the more chemicals it will be able to absorb and the longer it will keep on working. When it's full, it can't adsorb any more and has to be replaced. Impregnated carbon filters contain an additional chemical (a "chemisorbent") to eliminate certain chemicals like VOCs.



• Antibacterial and Germicidal Filters eliminate bacteria and germs. The IQAir Clean Room H13 HEPA Air Purifier, for example, utilizes a HEPA filter treated with agents to kill airborne microorganisms. Other air purifiers, like the AllerAir 4000 EXEC UV Air Purifier, use a UV lamp to kill germs. As antigens and pathogens pass over the lamp, it emits ultraviolet waves which alter their DNA, making them sterile and harmless. Air purifiers with UV filters are often used in sterile environments such as hospitals, kitchens, daycares, and labs. In residential use, they are great for controlling mold. If you are someone who gets sick often, an air purifier with a germicidal filter may be just what you need to give your immune system that extra boost.



• Pre-Filters remove large particles prior to primary filtration and come with nearly all air purifiers.

Other Factors to Consider Before Buying an Air Purifier

Air Pollution – Some air purifiers pollute the air with ozone, a powerful lung irritant that is especially dangerous for asthmatics, children, and the elderly. achoo! ALLERGY does not sell either ozone generators or ion generators because they both emit ozone, and they are not effective air purifiers.

Extra Features – These are the bells and whistles. They can make your air purifier a lot easier to use. On the other hand, they can also significantly up the price on an air purifier that isn't really all that much better than the next one. You simply have to decide which features will make your life easier and which ones just aren't worth the extra cash. For example, a filter change indicator light lets you know when to change the filter, and handles are important if you plan on moving your air purifier around a lot.
 

Warranty - A five-year warranty is a good one. A ten-year warranty is even better! Take into account what the warranty covers—motor, fan, electrical components? Also, find out if certain customer actions will void the warranty. Some manufacturers will void the warranty if the customer does not purchase replacement filters over the recommended time period; this can be inconvenient if you plan to run your unit less often or if the air in your home is cleaner than average.