Air Purifier Buying Guide

11 Critical Factors to Consider When Buying an Air Purifier

Choosing an air purifier for your residence or business can be a confusing task. There are literally hundreds of different models out there, and comparing one air purifier with another can be like comparing apples and oranges. Here are 11 factors to consider that can help you make the best decision for your environment:

  1. Effectiveness (Particulate Size Removal Capability)
  2. Method of Purifying Air
  3. Square-Footage Coverage & Cost per Square Foot
  4. Whole-Home or Whole-Office Coverage
  5. Replacement Parts Cost & Maintenance
  6. Strong Odor Removal
  7. Electricity Costs
  8. Noise Made by the Fan
  9. Warranty
  10. Size & Portability
  11. Guarantee

For more help in making your decision, also read Compare Technology. You can also call us toll free at 866-875-4386 for help selecting the right technology for your indoor air pollution problems.

1. Effectiveness (Particle Size Removal Capability)

Most HEPA air filters (the most effective type of filter, not air purifier) can remove 99.97% of particles as small as 0.3 microns from the air. However, most microbials are smaller than the 0.3 microns a HEPA air filter is capable of removing (See Common Airborne Particles and Their Sizes in Microns). HEPA air filters can remove smaller particles, but not very effectively or consistently.

Electronic air cleaners that utilize negative ions and low-level ozone (negative ion generators and ozone generators) are able to remove particles as small as 0.01 microns from the air, which is smaller than many airborne pollutants, but not all. Air Oasis Air Purifiers are able to remove particles as small as 0.001 microns, which includes viruses, typical atmospheric dust, pesticides and herbicides. To gain an understanding of the importance of the difference in particle size removal ability between air filters, ozone/negative ion/UV light air cleaners and Air Oasis, you need to consider the size of some of the most common indoor air pollutants.

For instance, fumes and viruses are too small to be captured by any air filtration device. Oxidation ions can remove many of the fumes and viruses. Very few tobacco smoke particles are large enough to be captured by filters, but most of these are large enough to be removed by ozone, oxidation ions and carbon. Some dust mites and bacteria are large enough to be captured by HEPA air filters, but most (all bacteria) are able to be removed by ozone and oxidation ions. A HEPA air filter can capture most mold spores and pollen that pass through them, however, the HEPA filter doesn't kill the mold unless the filter is chemically treated. Thus the mold continues to live on the filter, and when you replace the filter, the mold can be released back into the air. Ozone and oxidation ions can remove all that they come in contact with from the air, since they are emitted throughout a room or area.

Air Oasis has developed a scientifically advanced photo catalytic oxidation technology (AHPCO Cell) that combines the science of ultraviolet germicidal light waves, purifying hydroxyl ions, activated oxygen and photo ionization. What makes this technology important and unique is that it unites four of the most accepted and powerful methods for destroying (not just filtering) contaminants up to .001 microns, with the resulting synergy producing a stronger process than the sum of the individual methods. The Air Oasis Air Purifiers produces not only an atmosphere in which germicidal light can kill microorganisms like bacteria, viruses and fungi, it also produces super oxide ions, hydroxyl ions, hydro-peroxides, ozonide ions and negative ion to further attack micro-organisms and significantly reduce odors, VOC's, chemicals and fumes.

2. Method of Purifying Air

Many air cleaners are hampered by severe limitations. Air cleaners that rely on filters, such as HEPA filters, can only clean the air that is nearby, leaving most of your house, or even a single room, unpurified. In essence, the unit must drag the entire room into the air cleaner unit in order to clean the air. Thus, only a very small percentage of the air in just a single room will find its way through a stationary filter. Plus, air filters can serve as a breeding ground for mold and bacteria. And the dust that is collected provides the mold and bacteria microbes the nutrients they need to thrive. Filters can also spread illness when you handle the filters for maintenance and replacement purposes because as you remove the filter, the mold spores, bacteria and viruses can become airborne.

Even if you eliminate a HEPA air filter from consideration, it is still important to realize that all negative ion, oxidation technologies and ozone generators are not alike. Due to maintenance requirements, many electronic air cleaners use a fragile glass plate that could easily break. Glass plate technology also means lower reliability due to the fragility of the glass plates themselves, and also because they need to be cleaned frequently in order to work properly.

There are three ways an air purifier can actively produce negative ions: By high voltage electricity run through metal needles (needlepoint ionization), or passively, as a byproduct of when ozone is created by corona discharge or UV light. Needlepoint ionization is by far the most effective way to produce high volume negative ions. However, negative ions have a very short life (2 - 6 minutes) and die before they can circulate completely throughout a dwelling. Also, a high-powered ion generator can produce what has been termed "black wall", a black dust that settles on surfaces, in particular around the ion generator.

Understanding the limiting factors of negative ion production, the Air Oasis unit’s ultraviolet light produces enough negative ions to be beneficial in removing airborne particulates in a surrounding area and in helping change the ion balance in that environment, but without creating black wall. Surround Air Ionizers produce copious amounts of negative ions without creating black wall. If negative ions are only being produced as a byproduct of creating ozone, only a small amount of negative ions will be produced. As a result, with this method you will not see much improvement, if any at all, in the airborne particulate/allergen level. Also remember, negative ions cannot be transmitted "through" walls; the FTC has disallowed such claims.

3. Square Foot Coverage / Cost per Square Foot

A low price air purifier or air cleaner does not mean cost efficient. Many lower-priced air cleaners are actually costly when it comes to cost per square foot cleaned, the true measure of an air purifier's value. Most HEPA air filters are rated to cover 500 square feet or less, although they are typically similar in cost to oxidizer and negative ion air cleaners that can cover much larger areas.

To calculate the cost per square foot cleaned, simply divide the air cleaner's square-footage coverage into its cost. For instance, if the unit says it can clean 450 sq. ft. and costs $695, your cost per square footage is $1.54. Yet if it can clean 1000 sq. ft. for $399, your cost is $0.39 per sq. ft. You may also want to factor electricity consumption and filter replacement costs into your calculation to get a more accurate idea of "cost of ownership" and "true value provided". 

4. Whole-Home or Whole-Office Building Coverage

A single air purifier can rarely purify an entire home or office building regardless of how many square-feet it is rated to cover. This is due to the fact that walls, floors, ceilings, doors, etc. serve as barriers for air purifiers, even for those that use negative ions, oxidation and ozone.The best way to thoroughly purify the entire home is to use multiple air purifiers throughout the home, so each part of the home is within reasonable range of an air cleaner. However, this approach can be cost-prohibitive with most air purifiers. We do offer inexpensive Surround Air Ionizers and Airfree Air Sterilizers, which are affordable enough to buy one for every room. And many customers choose the Air Oasis 3000 for their living room/dining room/kitchen area and the Air Oasis Mobile for bedroom, offices and travel.

Another way to treat your entire house is with a HVAC induct model that works directly with your heating and cooling system to deliver oxidation air purification throughout the duck system and in every room served by the HVAC system. Air Oasis In-Duct Air Purifiers are designed to be installed directly into the existing central heating and air conditioning ventilating system's ductwork. They turn any central heating and cooling system into an air-cleaning machine to significantly reduce pollutants and contaminants in homes and businesses.

5. Replacement Parts Cost and Maintenance

Many air purifiers will actually cost more in replacement costs for parts, such as filters, in a single year than their original purchase price. Be particularly aware of air cleaners that use air filters. Air filters generally last about three to six months, and in many cases cost a couple hundred dollars to replace. As has been mentioned before, ionizer air purifiers and ozone generators that use needles or glass plates require frequent cleaning and maintenance. Plus, the glass plates break very easily and often need to be replaced. Ceramic plates are much less susceptible to damage, but they are still vulnerable.

The lowest maintenance air purifiers we sell are the Airfree Air Sterilizers, which have NO maintenance, and Air Oasis Air Purifiers, which only need the cell to be replacement once every two to three years.

6. Strong Odor Removal

If your primary need for an air purifier is to eliminate or reduce odors, then an air cleaner that uses oxidants, ozone or carbon will be necessary. HEPA and other air filters are not capable of removing most particles that cause odors, but oxidants or ozone can destroy most odor-causing particles and carbon removes them from the air. Negative ion-only air purifiers are not the most effective at removing strong odors either. They can help reduce odors to a degree, but are mostly effective at removing solid particles such as dust, pollens, animal dander, etc. If a negative ion air purifier also uses ozone, then it will be more effective at removing odors. But then you must be watchful that the ozone levels don't rise high enough to become an irritant. For odors, it is best to have an air purifier that automatically produces very low, safe levels of ozone so that the unit does not create harmful ozone levels that exceed safe levels (the EPS recommends no higher than .05 ppm).

Hydroxyl ions are also powerful against odors, especially chemical odors. Air Oasis air purifiers have this capability, making them perfect for stronger odors, including cigarette smoke, pet odors, cooking odors, etc. Air Oasis G3 5000PRO commercial air purifier is recommend for serious odor problems, like found in clubs, man-caves, smoky bars, kennels, food processing plants, nail salons and chemical odors.

If odors are the only problem you want to solve, Environmental Air Sponges are an excellent choice. We have never found an odor that they cannot remove, and they even pull the odors out of upholstery, drapes, wood and other materials.

7. Electricity Costs

It is also important to find out how much an air cleaner will cost in power consumption, since some can cost over $300 per year in electricity. To determine annual electricity cost, find the number of watts listed by the manufacturer of the air purification system you are considering and use the following equation to determine the annual cost in electricity needed to run the air purifier.

(Watts/1000)  X  (KWH-Kilowatt Hours)  X (8760) = Annual Electricity Cost


Divide the number of watts listed by the manufacturer by 1000. For instance, a Air Oasis 1000 uses roughly 40 watts:

40 divided by 1000 equals 0.04

Multiply the result by the number of Kilowatt Hours (KWH) you are charged by your electric utility company. You can find this on your electric utility bill, or you can use 0.10, which is typical.

0.04 x 0.10 KWH = 0.004

Multiply the result by the number of hours the unit will run on an annual basis. Unless the contamination level is extremely low, you will want to run your air purifier continually, so 8760 (24 hours times 365 days).

0.004 x 8760 Hours = $35.04 per year

In our example, the Air Oasis 1000 would cost $35.04 in annual electricity cost if the unit was operating 24 hours per day, 7 days a week (or $2.92 per month or $0.096 cents per day).

8. Noise Made by the Fan

Many electronic air cleaners, HEPA and carbon-based air filters utilize a motor in an attempt to draw more air through the air filter because the only air that is treated in that which passes through the air filter. Unfortunately, these motors can be very loud. Many negative ion and ozone generators may also be equipped with a fan, but these fans usually make quite a bit less noise than a fan you might place on a desk in the middle of summer.

All air purifiers we sell have a quiet setting, making them virtually silent, especially at the lower settings. Brands that use a fan to distribute the negative ions and friendly oxidizers evenly throughout a room don't need a powerful fan because negative ions and oxidizers can move around a room by using the rooms natural air flow, due to their electrical reactivity with the elements of the air. The difference is that instead of dragging the entire room into the air cleaner to purify the air, they send their purifying oxidizers to the air in your room, which also means that it doesn'tt take as long to purify the air in the entire room, as well adjoining rooms.

9. Warranty

Most air purifiers on the market come with at least a one-year warranty. If an air purifier offers something less or no warranty at all, this should raise a red flag in your mind. All air purifiers we carry come with at least a one-year warranty, and most come with a three-year warranty, except the Airpura commercial air cleaners, which comes with a five-year parts, ten-year labor warranty.

10. Size & Portability

It is a good idea to buy an air purifier that can be easily moved from room to room. In which case, you should check the dimensions and weight of the machine to determine if it is portable. Plus, you may want to place your air purifier on a shelf or within a certain spot on an end table. This is especially true since negative ion and oxidant air purifiers are more effective when placed higher. In which case, make sure you buy a unit that is compact enough to fit in such places.

For instance, Air Oasis Air Purifiers residential units weigh 6 pounds and are nearly as small as a shoe box, so they can be easily moved around. The portability also makes them easier to use for special treatments, such as purifying your bed and furniture of dust mites, sanitizing your bathroom and purifying the inside of your vehicle. On the other hand, an Airpura commercial air cleaner can weight as much of 50 pounds because of the hefty carbon filter and the metal case. While it comes with casters to easily move it around, moving it up or down stairs is not so easy.

11. Guarantee

Regardless of how wonderful an air purifier may seem from what you hear or read, you never know for sure whether it will result in a noticeable difference in your particular environment until you have one. Therefore, you should find a supplier that offers a money-back guarantee, preferably without a restocking fee.. This way, you will not be out a couple hundred dollars or more if the air purifier does not work the way you hoped it would.

At, we only sell products that the manufacturer warrants, plus we offer a 30-Day Money Back Guarantee on every product we sell, no exceptions. And, that guarantee doesn't begin until you receive your product. Additionally, we have unlimited free customer support Monday through Friday, 8:00am to 4:00pm PST. 

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