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An air purifier without an activated carbon air filter is only half an air purifier Just as in the case of other air purification technologies, the activated carbon air filter is misunderstood, misleadingly advertised, and mistakenly dismissed as unimportant. Ionic type air purifiers do not use one at all. Air purifiers promoting their HEPA or HEPA-type media may include a thin fibrous pad with a few token ounces of activated carbon. How should you, as a consumer, evaluate these products? Will they do for you all that you expect from an air cleaner? Or should you insist on something more? The very companies that should help make your decision an easier one often do just the opposite. Unfortunately, one of the most frustrating things about searching for air purifiers is the prevalence of hype and the absence of real information. Rather than follow suit and toss dozens of alarming “quotes from experts” at you, I hope to answer some of the most basic questions you may have. What can an activated carbon air filter really do for you? Will activated carbon filters prove to be your only real defense against chemicals and odors? How does activated carbon work in air purifiers? How much do you need? How can you evaluate which air purifiers are best for your needs? No other air purifier technology comes close to removing the volume of chemicals that activated carbon does. If you’re serious about making the best possible choice in air purification, why not take the time to review the information in this article?

What can an activated carbon air filter do for you?

Air purification with activated carbon air filters is the single best way to remove chemical pollutants from the air. An activated carbon filter will adsorb some of almost any vapor, especially organic molecules and solvents. Activated carbon can adsorb and retain a wide variety of chemicals at the same time. Activated carbon air filters work well under a wide range of temperatures and humidity levels; are inert and safe to handle and use; and are readily available and affordable. While activated carbon does remove many volatile organic compounds (VOCs), some compounds like formaldehyde and inorganic gases respond best to chemisorbers that break down the pollutants by chemical reaction. You should look for air purifiers containing activated carbon impregnated with appropriate chemisorbers and catalysts to control the particular pollutants that concern you.

How does activated carbon work in air purifiers?

When gases, chemicals and odors pass slowly through a thick filter packed with activated carbon they become trapped in the million of pores opened by the activation process. Due to the large internal surface area of activated carbons it can adsorb up to 60% of its weight. Good carbon filters, depending on the environment in which they are used, can last up to 5 years before all of the pores are full.

What should you look for when choosing your activated carbon air cleaner?

Is protecting your family from airborne chemical toxins important to you? Would you like to control unpleasant odors from cooking, cleaning or smoking? Do you have sensitivities to volatile organic compounds? An activated carbon air filter is the best way to accomplish these tasks, but will just any old purifier claiming to have activated carbon be good enough? Many air purifiers claim to use activated carbon for gas and odor removal, but will not mention how much is in their filter. In an average home, that small amount of carbon could get saturated in days, even hours. After this, the filter would need to be replaced or it would be doing nothing. For an activated carbon filter to be effective, there needs to be a sufficient amount of activated carbon so the air passing through is able to deposit its pollutants. When choosing an activated carbon filter it is important to find one that provides a large activated carbon bed weighing many pounds. Additionally the activated carbon media needs to be protected from premature clogging by being placed behind a pre-filter. An optimal flow of air needs to be available to pass through it. A cylindrical shaped design is an ideal solution for allowing maximum contact with the air. It is best if the air filter’s activated carbon bed and HEPA filter can be replaced separately as the activated carbon filter will typically have a shorter life than the HEPA filter. They both should be relatively easy to access and replace, preferably without tools. Another point to look for is whether you can replace the activated carbon media itself without replacing the entire containing cartridge. Bulk media is much less expensive than a complete cartridge unit. Among the best air purifiers offering activated carbon air filters are Allerair, IQAir, Blueair, and Austin Air. 

How to Achieve Superior Air Purification with Activated Carbon Air FiltersIs protecting your family from chemical air pollution important to you?

Activated carbon air filters will prove to be your only real defense against chemicals and odors. No other air purifier technology even comes close to removing the volume of chemicals that activated carbon does.

Consider why we use activated carbon for air purification. Only activated carbon removes gaseous chemical pollutants. Many troubling effects chemicals can cause you and your family to suffer include:

• Cancer
• Depression
• Dizziness
• Dryness and irritation of the eyes, nose, throat, and skin
• Fatigue
• Headache
• Hypersensitivity
• Irritability
• Lightheadedness
• Multiple Chemical Sensitivity (MCS)
• Memory loss
• Nausea
• Symptoms similar to a cold

How Can Activated Carbon Air Filters Benefit You?

Featured Site What Is Activated Carbon? Learn more at Wikipedia

Most persons looking to buy an air purifier initially do so to relieve an allergy or asthma condition and often think only in terms of particulate irritants like dust, pollen, and dander.

With a little research they discover the substantial negative health effects of the odors and chemicals they are exposed to in their homes and workplaces. It’s because of the ill health effects of chemical contaminants and the need to control them that better quality air purifiers include activated carbon air filters.

Activated carbon air filters can adsorb some of almost any vapor; have a large capacity for organic molecules, especially solvents; adsorb and retain a wide variety of chemicals at the same time; work well under a wide range of temperatures and humidity levels; are inert and safe to handle and use; and are readily available and affordable.

Activated carbon air filters can make the air healthier for people in general, but especially asthma sufferers, babies, children, the elderly, and are particularly helpful to people with Multiple Chemical Sensitivity (MCS).

How To Choose The Best Activated Carbon Air Filters

Numerous air cleaners promise you the benefits of purification with activated carbon. What do you really need to know to judge your familys needs accurately?

First, differing chemicals and odors may require activated carbon with differing properties. These properties result from the source of the activated carbon, the methods used to create it, and any added chemisorbers and catalysts. These catalysts and chemisorbers enhance the adsorption of specific pollutants.

This allows you to select the specific activated carbon air filter for your needs. However, few air purifier manufacturers offer you any opportunity to select a custom carbon blend.

What about the quantity of carbon? Is an air cleaner offering only a simple activated carbon filter pad with a few ounces of activated carbon sufficient? Should you look for an air purifier that includes an activated carbon bed weighing many pounds?

For an activated carbon filter to be effective, there needs to be a sufficient amount of activated carbon so that the air passing through the filter is able to deposit its pollutant molecules.Most air cleaners on the market today include a foam or fibrous pad onto which a few ounces of carbon have been applied. This is so they can claim a broader range of air cleaning capabilities, but in reality such small quantities of carbon are ineffective.An activated carbon filter needs a deep bed consisting of many pounds of activated carbon to provide sufficient dwell time for the air passing through it to achieve maximum removal of pollutants.

The activated carbon pads found on most filters are also usually part of a pre-filter design that is intended to prevent large particles from prematurely clogging a higher efficiency filter placed behind the pre-filter. Unfortunately this allows fine dust particles to clog the micro pores of the activated carbon and results in very rapid reduction in its effectiveness.When choosing an activated carbon filter it is important to find one that provides a large bed of many pounds of activated carbon. Additionally the activated carbon media needs to be protected from premature clogging by being placed behind a pre-filter.An optimal flow of air needs to be available to pass through it. A cylindrical shaped design is an ideal solution for allowing maximum contact with the air.

To capture any carbon dust that may be lost from the activated carbon filter a post filter should be placed after the activated carbon and in front of any other high efficiency filter such as HEPA.

It is best if the air filter’s activated carbon bed and HEPA filter can be replaced separately as the activated carbon filter will typically have a shorter life than the HEPA filter. They both should be relatively easy to access.

Finally, you should be aware that while activated carbon is excellent for removal of highly volatile organic compounds (VOCs), less volatile compounds like formaldehyde and inorganic gases respond best to chemisorbers that break down the pollutants by chemical reaction. Thus, you should look for an activated carbon filter that is impregnated with appropriate media to control the particular pollutants that concern you.

I have found that Allerair air purifiers, with over forty different activated carbon blends available for almost any general application can meet anyone’s needs with ease. Allerair can also provide highly customized blends for special purposes to labs, industry, military or anyone with needs beyond the usual residential, healthcare, or commercial uses.

If you’re going to buy an air purifier, it only makes sense to purchase one that can control practically anything.

Is A HEPA Filter Really Necessary? Should you choose a HEPA filter over other alternatives?

At first glance there may seem to be added expense in your initial purchase. You may feel that replacement filters will expensive and cumbersome. With so many air cleaners promising to be “silent” or have “no messy, expensive filters” you might feel that HEPA filter air purifiers are a second rate option. Is the marketing of well-heeled consumer product companies really doing justice to this mainstay of air purification?

I feel that many people are being misled by the disinformation of irresponsible marketing campaigns. That is one of the reasons for building this site. Multiple chemical sensitivity, allergy and asthma are problems I am personally familiar with. So finding effective air purification systems has been a priority in my life for the last fourteen years.

Ultimately I came to the conclusion that a HEPA air filtration system is the best solution available. I believe that you too will benefit from a HEPA air cleaner.

To explain why let’s start with the most basic questions you should ask when deciding on an air purifier.

Questions you should ask of any air purifier

• What will the air cleaner remove from the air? What will it not?
• How efficient is the air purifier? How effective is the technology it uses to clean the air?
• What size of air cleaner will I need? How many air changes per hour will it provide in that size room?
• How easy is it to change or clean the filter? How often is this maintenance necessary? What our the cost and availability of the filters?
• How much noisey is the sysyem, can I run it when I am asleep.?

With these questions in mind, how effectively does HEPA air filtration give the results you’ll be most satisfied with?

Evaluating HEPA air filtration

What will a HEPA filter remove from your home air? What will it not?

HEPA filters can also capture irritant particles like tobacco smoke. Usually some form of prefilter is used to trap larger dust particles that would prematurely clog the higher efficiency HEPA filter placed after it.

HEPA filters will not remove chemicals and odors. This is why they are often combined with activated carbon filters.

Of course, all filtering systems likewise claim to remove such particles. They likewise need to be supplemented in some way to remove odors and chemicals. The real advantage of HEPA air filtration is seen in its overall effectiveness versus these other air cleaners.

What is the efficiency rating of HEPA? How effective is the technology versus other air cleaning systems?

Only HEPA air filtration meets a standard recognized by government and industry. To receive the HEPA designation it must remove 99.97% of all particles as small as 0.3 micron in size.

While other filter media remove some particles at that size their efficiency varies and is often no greater than 50%. Even much larger particles like pollen may not be fully removed. The problem with non-HEPA filters is you have no way of knowing how effective they are.

Ion generators do not remove particles at all. Their method is to fill the air with charged particles that tend to attract other particles. These stick together and presumably settle out of the air more quickly. Some charged particles will stick to the walls and furnishings. This has been called the “black wall effect”. The EPA has expressed concern that these uncollected charged particles may even deposit within the lungs of exposed persons.

Ionic air cleaners that use collector plates are called electrostatic precipitators. Their efficiency at particle collection tends to be no greater than 80%, much less than HEPA air filtration. Studies have shown that the collection efficiency can be reduced to as little as 20% in as few as three days due to particle loading of the collector plates.

Some people claim that ozone generators clean the air by destroying the contaminants. Scientific studies have shown this to clearly not be the case. Ozone can react with pollutants but the partial breakdown byproducts that result can be more numerous and more dangerous than the original pollutants. Ozone generators’ efficiency at removing contaminants is essentially zero.

If you really want the most effective air cleaning available then HEPA air filtration is your best choice.

Will the air purifier clean the air in a room as large as you need? How many air changes per hour will it provide in that size room?

HEPA air filtration is the most effective means to clean large volumes of air rapidly.

Of course, these air purifiers come in a wide variety of sizes allowing you to choose according to your needs. Some Allerair air cleaners reportedly cover areas as large as 1800 sq. ft. However, that is at a reduced number of air changes per hour. Even so, the total capacity of these fan forced air cleaners is always far greater than other systems.

In ionic air cleaners that use no fan the speed of ionized air being pulled through the unit is quite low. This means a very much-reduced ability to clean large volumes of air.

Where ionic air cleaners have an added fan the air speed has to be kept low also. This is because a fast moving air stream would not permit the charged particles to be deflected onto the collector plates. Again, you don’t get the ability to clean large volumes of air quickly.

How easy to change the filter? How often is this maintenance necessary? Cost and availability of the filters?

One of the greatest scams in the air purifier market among non-HEPA air cleaners is to sell a cheap air purifier and then bilk the customer later with pricey regular filter changes. Sometimes the filters are hard to come by, either the store selling the air cleaner doesn’t carry the filters or is chronically out of stock.

The actual cost of a replacement HEPA filter may seem high compared to a non-HEPA filter. However, consider that replacement may be once every two, five, even eight years in the case of the Allerair AirMedic. This means the annual cost to have clean air is low by comparison.

With ionic air cleaners you avoid the cost of replacement filters but cannot avoid the necessity of constant maintenance cleaning of the collection system. Many owners have complained at how difficult it is to properly clean closely spaced collector assemblies. A collector grid that isn’t cleaned regularly doesn’t clean the air and can develop a residue on the plates that will not come off. This permanently reduces its ability to clean.

HEPA air filters are very easy to change. Manufacturers have made certain tools are never required and most can be completely replaced in less than five minutes.

All things considered, HEPA air filtration is simple, easy, low maintenance and low in long term cost while offering the best air cleaning possible.

How much noise does the filtration system make? Is it quiet enough to run while you sleep?

HEPA air filtration tends to be the noisiest because of the fan forcing air through the system. However, high quality HEPA air purifier manufacturers recognize this and do their best to keep noise levels as low as possible. All offer low speed settings that are quiet enough to sleep without disturbance.

If you choose the right size air purifier it will be able to give sufficient air changes per hour at a lower speed setting. This keeps noise low and gives you additional cleaning capacity at a higher setting in the event it is needed, like after a cooking mishap.

Ionic air cleaners may have an edge in the “silence is golden” department, but this comes at the expense of performance.

I encourage you to put greater value on air cleaning performance and choose HEPA air filtration.

If you would like to consider air purifiers from companies that keep your needs in mind and offer truly effective and reliable air purification IQAir, Allerair, Austin Air and BlueAir are among the best.

Is a filterless air purifier equal to the hype? Is a filterless air purifier right for you? Would you like to know more about the limitations of filterless purifiers before you make your final decision?

I understand that you sincerely want to make a good decision when it comes to your family’s health. Shouldn’t you have as complete an understanding of the facts as possible? The marketing behind filterless air cleaners can be very compelling. However, like all marketing, it can be very biased, presenting only the most favorable information for their products. Often, real and imagined “deficiencies” of competitors are exaggerated well beyond what is reasonable. This is certainly the case when it comes to “no filter” air purifiers. In one advertisement after another you find air cleaners based on varied technologies proclaiming “no filter replacement”.

Oh, how difficult it must be changing filters, since the filter free purifiers insist on how you need no tools.

Oh, how messy filters must be to replace, they imply as they show some poor woman gagging on dust.

Oh, how expensive filter replacement must be, with some vendors quoting costs in the thousands. But is a filterless air purifier really the ideal solution to your air quality problems?

What are your filterless air purifier choices and how do they work?

Allow me to introduce you to the primary technologies found in filterless air cleaners:

• Electrostatic precipitators(often called ionics by vendors)
• Ion generators (the true ionic cleaner)
• Ozone generators
• Photocatalytics
• Plasmacluster ionics

The electrostatic precipitator

The electrostatic precipitator charges particles in the air and then uses a series of collector plates with an opposite charge to attract the particles to the plates. It is possible for particles as small as 0.1 micron to be collected this way.

The ion generator

True ionizers simply emit ions into the air. These attach to airborne particles and cause them to aggregate into clumps until they fall to the floor or stick to walls, draperies, or furniture. While these filterless air purifiers help clear the air the dirt is not removed permanently.

The ozone generator

Ozone generators purposefully have ozone emissions that push the limits of what is considered acceptable for human exposure. The claim is that ozone destroys particles and gases and odors and that it is healthful to breathe. The scientific consensus is that such claims are completely false. This is the position the US Environmental Protection Agency and Federal Trade Commission take. Until the law is strengthened, these devices will continue to be marketed as air cleaners and continue to do harm.

The photocatalytics

Plasmacluster Ions

A new technology developed by Sharp. These ions are drawn to airborne contaminants like bacteria and viruses by their electrical charge. The ions surround the contaminant and form hydroxyl radicals that ultimately destroy the contaminant. This technology has been proven effective against biological pollutants like mold, pollen, viruses and bacteria as well as chemical and particulate contaminants. But this technology is also generally combined with filtration.

What are the top ten drawbacks of filterless air purifiers?

1. Low efficiency. Scientific evidence indicates that home ozone generators are all but zero percent capable of cleaning the air. The best models of electrostatic precipitators only achieve about 80% efficiency at particle removal. Ion generators have some effect but precise measurements are hard to come by, and besides, any particles they help settle out of the air are easily disturbed and reintroduced into the air. Photocatalytic and plasmacluster air cleaners work best on only the smallest of particles.
2. Rapid loss of efficiency. Loading of electrostatic precipitator collector plates with captured particles rapidly degrades efficiency at collecting further particles. Efficiency can be reduced to below 20% in as few as three days. CADR (Clean Air Delivery Rate) labels on air cleaners indicate that the stated performance refers to the first 72 hours of use. This is because the voluntary testing is limited to 72 hours, primarily due to the fact that manufacturers know their products cannot sustain high efficiency. Ozone generators are worthless to begin with. Ion generators can suffer from corrosion and contamination of electrode pins and wires, reducing their ability to generate ions. Similar contamination buildup on the semiconductor plate of photocatalytics can reduce effectiveness.
3. Constant maintenance. The rapid reduction in collection efficiency due to electrostatic precipitator plate loading requires regular maintenance cleaning. From twice a week to daily is recommended, depending on the environment. This sounds like a lot of work for the “benefit” of a “no maintenance”, “no filter replacement” filterless air purifier. Ion generators also need regular maintenance of their electrodes, cleaning them with an alcohol swab.
4. Reduction in efficiency over life of unit. Even with regular maintenance cleaning, collection efficiency will degrade due to deposits that simply cannot be removed. This is an even greater problem when cleaning is not regular. This degrading over the life of the unit can effect all filterless air cleaner technologies.
5. Short life. Corrosion of the ionizing wire or needlepoint ionizing pins, electrical failures of the high voltage systems, and other problems can lead to product failure. Hence, warranties of filter free air purifiers tend to be far shorter than the five to ten years available on better quality HEPA air purifiers.
6. Ozone production. Electrostatic precipitators and ozone generators produce ozone, a hazardous gas that damages the tissues of the airways causing increased sensitization to allergens, difficulty breathing for asthmatics, and possible severe respiratory distress. Photocatalytic and plasmacluster air cleaners are ozone free.
7. Limited area due to low airflow. The need for ionized particles to spend sufficient time in the air electrostatic precipitators to be charged and then deflected onto the collection plates means air speed must be low. This limits the amount of clean air that can be delivered by the units. Likewise other filterless air purifier systems also tend to demonstrate much lower clean air delivery than can be achieved by a good HEPA filter air purifier. Of course, clean air delivery for an ozone generator is essentially zero, especially since ozone is itself a pollutant.
8. No effect on gaseous contaminants. Chemical toxins, mold mycotoxins, volatile organic compounds, formaldehyde, the hundreds of chemicals in cigarette smoke all pass through an electrostatic precipitators unaffected. Ion generators likewise have no effect on chemical pollutants. Ozone generators, while marketed as being able to destroy these contaminants have consistently failed to do so in scientific studies. What is more, breakdown products of ozone oxidized contaminants have been shown to be more toxic than the original pollutants and more numerous. Photocatalytic and plasmacluster air purifiers do show excellent promise in handling chemical contaminants.
9. Black wall effect / Black lung. Ionized particles created with an ion generator will collect on walls, furniture, or any available surface. This includes the inside surface of your lungs. This effect has been given a name. It’s called the black wall effect. The EPA has noted the health hazard of negatively charged respirable particles adhering to your lung tissues. See: Possible effects of particle charging
10. Arbitrary pricing serves as no guide. Testing often shows that high priced filterless air purifiers may perform no better or even worse than cheaper models. Consumer Reports has periodically tested a number of the market leaders in this category and given them poor ratings due to inadequate performance and ozone production. Quality of materials and construction, durability, and effectiveness do not seem to play a consistent role in pricing. Rather, it seems the basis for price is simply what the market will bear and what their advertising budget can convince people to pay for the promise of clean air.

Are there filterless air purifier alternatives?

It’s very understandable to want an air purifier that is effective, reasonable in cost, low maintenance, and has low long term cost of ownership. That’s why a filterless air purifier appeals to so many.

The idea of “filter free” seems to solve maintenance and long term cost issues. Unfortunately, this isn’t really the case, and effectiveness tends to also be sacrificed. Plus, the initial cost of these air cleaners can often equal that of a good HEPA air cleaner.

There are better alternatives to “no filter” air purifiers that really can be reasonable in total cost and easy to live with. Allerair air purifiers and Austin Air air purifiers are two that stand out.

These two manufacturers both offer a variety of models that are reasonable in initial cost, use filters that last up to five years and are economical and easy to replace with no tools.

Should you consider an air ionizer? One of the most confusing terms in the field of air purification is the air ionizer. In one advertisement after another we find air cleaning devices with widely varied technologies claiming to ionize the air. So just exactly what are we talking about when we use the term “air ionizer”.

The one thing that all these air cleaning devices have in common is they are a form of electronic air purifier. Electronic air purifiers use a high voltage wiring system to create an electrical charge that results in particulates passing through becoming negatively charged.

But after that the similarity ends and a whole host of differences begin to show up. Some use collector plates and some don’t. Some have a fan and others don’t. Some use a charged media filter and others use various mechanical filters including HEPA type filtration. Some use the ionization potential to deliberately create ozone and some attempt to reduce ozone byproducts with catalysts. Finally, there are the hybrids that mix and match approaches, sometimes including as many as five different technologies.

It’s no wonder that comparing air ionizer air cleaners is confusing. How can you know what is effective? Are there any that should definitely be avoided?

The vast field of products renders it ridiculously difficult to evaluate air ionizers individually. However, it is possible to break down the basic technological approaches used and determine if any one or combination is worthwhile.

The primary technologies found in air ionizer devices are:

• The electrostatic precipitator
• The negative ion generator
• The ozone generator

Each of these receives a brief overview below.

The electrostatic precipitator

The electrostatic precipitator uses a series of collector plates with a charge opposite that of the ionized particles. This results in a powerful electrostatic attraction that pulls the particles to the plates like a magnet.

It is possible for particles as small as 0.1 micron to be collected this way. Since this is smaller than the 0.3 micron rating of HEPA filters you will sometimes see claims that these devices are better than HEPA. However, it must be pointed out that even the best electrostatic precipitators are only 80% efficient. Compare this to the 99.97% efficiency of a HEPA filter.

Apart from the poor initial collection efficiency is the additional flaw that the plates progressively lose efficiency as material is collected. Research shows that in as few as three days you can lose as much as 80% of the collection efficiency of clean plates. This means your electrostatic precipitator will only be attracting about 20% of the particles passing through it. Regular maintenance cleaning is an absolute necessity. At a minimum, the collection plates should be cleaned twice a week and every day would be best in order to achieve maximum efficiency.

On a final note, electrostatic precipitators will produce ozone in sufficient quantities to be an irritant to many people, especially those with pulmonary related illnesses like asthma.

The negative ion generator negative ionizer no collector and brief faults

The ozone generatorozone generator and faults

Eleven ways air ionizers underperform

1. Low efficiency. Even the best models only achieve 80% efficiency at particle removal. They are unable to clean the air to HEPA standards.
2. Rapid loss of efficiency. Loading of collector plates with captured particles rapidly degrades efficiency at collecting further particles. Efficiency can be reduced to below 20% in as few as three days.
3. Constant maintenance. The rapid reduction in collection efficiency due to plate loading requires regular maintenance cleaning. From twice a week to daily is recommended, depending on the environment.
4. Reduction in efficiency over life of unit. Even with regular maintenance cleaning, collection efficiency will degrade as constant bombardment from high energy ions corrodes the needlepoint ionizers or ionizing wire.
5. Short life. Corrosion of the ionizing wire or needlepoint ionizing pins by ion bombardment will result in failure of the air ionizer. Hence, short warranties.
6. Ozone production. All air ionizers produce ozone, a hazardous gas that damages the tissues of the airways causing increased sensitization to allergens, difficulty breathing for asthmatics, and possible severe respiratory distress.
7. Limited coverage area. Government regulations on ozone exposure levels effectively requires manufacturers to balance the ionization potential of their units against the level of ozone produced. This serves to limit the area an ionizer can effectively clean. This means that you must buy multiple units to achieve the same coverage area as a single HEPA purifier may be capable of handling.
8. Limited area, part II. Low air flow. The need for ionized particles to spend sufficient time in the air ionizer to be deflected onto the collection plates means air speed must be slow. Thus, air ionizers often use no fan or a low speed fan. Low air flow means low air volume handled by the unit and thus significant limitations on the size of the area that can be cleaned. Again, you must buy several units to achieve the coverage of a single HEPA air purifier.
9. No effect on gaseous contaminants. Chemical toxins, mold mycotoxins, volatile organic compounds, formaldehyde, the hundreds of chemicals in cigarette smoke all pass through an air ionizer unaffected.
10. Black wall effect / Black lung. Ionized particles not collected on plates in the electrostatic precipitator or by design with a negative ion generator will instead collect on walls, furniture, or any available surface. This includes the inside surface of your lungs. This effect has been given a name. It’s called the black wall effect. The health hazard of negatively charged respirable particles adhering to your lung tissues has been noted by the EPA. See: Possible effects of particle charging
11. Arbitrary pricing serves as no guide. Testing often shows that high priced models may perform no better or even worse than cheaper ones. Quality of materials and construction, durability, and effectiveness do not seem to play a consistent role in pricing. Rather, it seems the basis for price is simply what the market will bear for the promise of clean air. This situation is often pointed out by the sellers of air ionizers themselves.