Air Purifier Buying Guide

Common Household Air Pollutants

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

• Airborne Particles include pet dander, 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 is 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.
   
• Micro-organisms include antigens, pathogens, bacteria, and viruses. They are the everyday germs that make us sick. Mold is also considered a micro-organism.

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 is 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.
  
  
• 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 by rendering them harmless or trapping them within the filter media.



• 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 5000 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.



• 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 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.
  
 

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

Air Purifiers for Pollution Control

Controlling the source is the absolute best way to contain air pollution or contamination.  For example, if there is a smoker in the house and another person living there does not like the smell of smoke, the smoker should cease smoking in the house.  The same idea goes for pet odors, fumes, etc.  If something or someone is generating unpleasant or noxious fumes, control should begin at the source.  However, when air contamination cannot be contained at the source, air purifiers help control the odors, smoke, and pollution.  Often with beloved pets and even beloved smokers, source control is impossible or undesirable.

Air Purifiers Proper Placement

As a general rule, it is more difficult to filter the air in a large and open space (see the previous air exchanges section).  Large living rooms and family areas, especially those with abnormally high ceilings, present a challenge to effective air filtration.  Our rule with larger rooms is to attempt to direct the purified air exhaust from the air purifier to the vicinity of the room’s inhabitants.  Many of the machines we sell have directional outflow registers.  This allows the user to dictate where the clean air cycle begins and ends.
We suggest purchasing air purifiers for the bedroom first.  Place the unit 6-10 feet from the headboard of the bed with the directional registers pointing at the bed.  If the unit is too close, you will feel the draft from the unit.  If the unit is too far away from the bed, the cleanest air from the air purifier will not be breathed.  In the world of clean air, a smaller space is easier to effectively clean.  This is one reason why we suggest starting in the bedroom.  In addition to spending the majority of your life there, it is usually smaller than the other living areas of your home.

According to the majority of the air purifier manufacturers we work with, placing the unit near to where you are going to be is the norm.  Ideally, place the unit between 5 and 10 feet from where you spend your time.  Within the bedroom, the unit should be pulled out about a foot from the wall.  We have debated if there is benefit to elevating the air purifier off the ground.  In our opinion, it is not necessary.  Gravity is pulling particulate down; and as it gets lower to the ground, the intake suction of the air purifier should pull the air and particulate towards the machine.  Most air purifier manufacturers implement a bottom to top airflow--meaning the air is pulled into the machine at the bottom and released towards the top.  A long time ago when Honeywell Enviracaire made the only air purifier, their models pulled in from the top and exhausted downwards towards the floor.  This system runs counter to the conventional wisdom of working with gravity to create air circulation.  Fortunately their designs have changed for the better and other manufacturers have followed and further innovated with better air flow circulation in mind.

Air Purifiers Performance and Limitations

Air purifiers will not perform miracles.  Quality air purifiers create an air cycle in a one room environment and filter that air through quality filter media.  The filter media is usually HEPA cloth, carbon, or a combination of the two.  Ideally the machine will filter the entire volume of air in the room 4-6 times per hour.

The effectiveness of an air purifier varies on two things:  the sensitivity and severity to the allergen the user is trying to reduce exposure to and the relative strength of the contaminant or pollutant. 

One of the easiest particulates to filter from the air is dust.  Dust is abundant and omnipresent.  Some of the hardest airborne particulates to filter are cat dander and toxic chemicals.  Cat dander sticks easily to fabrics and stays aloft for a long time.  If a cat allergy sufferer wants to try an air purifier, we suggest they start by placing a unit in their bedroom and exercising limited source control.  Politely and lovingly, keep the cat (the source of the dander) out of the bedroom. 

Many fumes and toxic chemicals fall outside the adsorption spectrum of the majority of filter media.  To filter out a wider range of chemicals and gases, air purifier manufacturers introduce different types of media.  Highly absorptive carbon has an extremely large surface area to size ratio.  This characteristic helps carbon adsorb particulates.  Other similarly porous derivatives, like potassium permanganate and zeolite, are also used.  Potassium permanganate is an oxidizing agent that does not generate toxic byproducts.  Two other uses of potassium permanganate include:  being used as a disinfectant for treating humans and animals, and being used to clean and filter well and waste water.  Zeolite also has a micro porous structure.  The name is derived from the Greek word which means “stone that boils”.  Zeolite forms naturally where volcanic rock and ash layers react.  Natural zeolites often are excluded from commercial applications.  Zeolites are widely used in both domestic and commercial water purification as well as air purification.

Air Purifiers Fans and Motors

A question we field multiple times per day is, “Should I leave my air purifier on all the time?”  The answer is an emphatic “Yes!” (Unless there is an unusual circumstance like you are leaving on a 3 month vacation).  Air purifier motors are quiet, very energy efficient, do not consume a large amount of electricity, do not get hot, and easily maintain a constant RPM.  An air purifier can not clean the air if it is not turned on.  In fact, we recommend turning your air purifier on its highest setting when you are away.  This promotes maximum CFM output and air exchanges per hour.  The highest fan speed setting is usually too loud to tolerate when you are in the room, which is why we suggest running it on the highest setting when you are absent from the room.

Air Purifiers Benefits vs. Side Effects

Some of the many benefits of using an air purifier in your home or office include:  breathing less contaminated air, keeping your allergen load below its reactionary threshold, sleeping and breathing better, and living healthier naturally.  The side effects of using an air purifier are very small:  energy cost (similar to the use of a 60w light bulb) and white noise.  Actually, most people unknowingly benefit from the white noise from air purifiers.  White noise drowns out distracting background noises that can interrupt sleep.  White noise also helps people relax.  For these reasons, white noise is used widely in sleep centers throughout the country.

Air Purifiers Associated Cost

In addition to the acquisition cost, you should factor in the cost of replacing the filters.  We sell very good air purifiers that are very quiet; but, you have to change the filters more frequently for this luxury.  The piece of mind of changing an air purifier filter as recommended is priceless.  The motor and the filter work more efficiently when the filter is clean.

Wash or Replace Pre-Filters

A debated subject in our company is whether you should wash or replace pre-filter media?  It is a personal decision.  Pre-filters capture the large particles and need to be replaced more frequently.  Some people do not mind ordering a few extra filters and simply throwing away the old filters when it is time to replace.  Other people have no problem removing the old pre-filter, rinsing it through water, and allowing it to dry thoroughly before replacement.  As long as you do one or the other, we do not foresee any problems.  

Beware of Scams and False Advertising

As the case with many industries, there are good guys and bad guys.  According to the EPA as well as Consumer Reports, many manufacturers falsely advertise that ozone cleaners are air cleaners.  This is false.  There is actually a consumer alert out issued by the EPA.  The bottom line is ozone generators do not clean the air.  They charge the air using electricity which makes molecules generally heavier so they fall to the ground.  Our concern, as well as the Environmental Protection Agency's and Consumer Reports, is that ozone generators do just that; they generate ozone.  Ozone is a harmful lung irritant.  Another name for an ozone generator is an electrostatic precipitator.  Buyer beware, if it sounds too good to be true, then it probably is.  Again, air purifiers will not perform miracles.  Many bars and restaurants use ozone generators, because they claim to help with alleviating cigarette and cigar smoke.  We have no proof that this claim is true.  Ozone is a concern because it is a threat to users.  There is currently no standard for acceptable ozone levels.

Before You Buy

Before deciding to buy, take some time and research your purchase on our website, and read some articles on air purification products.  Do not buy an ozone generator that is marketed as an air purifier.  The Sharper Image was successful at marketing one of these units, but look where it got them.  Because of the false benefits of its proprietary Ionic breeze machine, they are now bankrupt due to class action litigation filed against them.  The scary part for consumers is that prior to the litigation, the Ionic Breeze was the most popular selling air purifier in the world.  Infomercials and media blitzes worked for them in the short term, but the company failed to provide a product that added lasting value.  To clean the air, you must have a fan and a filter.  The Ionic Breeze had neither.  We pointed out this flaw in our first air purifier review in 2002.

Easy Returns

Another question to consider when buying an air purifier is what if you do not like the unit after purchase? What if the air purifier is not for you?  In addition to offering free lifetime technical support on all the air purifiers we carry, we offer the most liberal return policy in the industry.  We have a 60 day policy on all returns.  In the event you buy an air purifier from us and want to return the unit, the process is hassle free.  You speak directly with a customer service representative, or you simply fill out a return authorization form to begin the process. We ask only that you keep all the original packaging and contents so that we can work with the vendor on a return. If you received promotional free shipping, you will be liable for the shipping costs and the return shipping to get the unit back to us or the appropriate vendor.

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. AchooAllergy.com does not sell either ozone generators or ion generators because they both emit ozone. 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 are not simply worth the extra cash. For example, a filter change indicator light lets you know when to change the filter, and handles or casters are important if you plan on moving your air purifier around a lot.
 

Warranty - An Austin Air air purifier comes with a five-year warranty. Another manufacturer called AllerAir offers a ten-year warranty. Be sure to consider 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 stipulation can be inconvenient if you plan to run your unit less often or if the air in your home is cleaner than average.

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