Here are the 9 types of air cleaning technology most commonly used in whole-house air purifiers and portable units:
- Fibrous Media [e.g: HEPA]
- UV Light
- Photocatalytic Oxidation
- Electrostatic precipitators
- Adsorbent Media [e.g: Activated Charcoal
- Chemisorbant Media
The research supporting this article is from The United States, Environmental Protection Agency [EPA] from their 2018 report on residential air cleaning technology.
1. Fibrous media air filters
These filters work by filtering any harmful particles by trapping them into the fibrous fiber components. Several factors affect the efficiency of these filters like the thickness of the filter, filter porosity, and so on. When excessively loaded they tend to decrease their efficiency. This requires you to replace these filters as per the manufacturer’s recommendation. Moreover, there are different types of fibrous media filters.
First is flat air filters which are mostly used in residential furnaces and air conditioning systems and are regarded as high-efficiency filters. Secondly, HEPA filters remove the finest particles thus considered the best type of fibrous media filters. They trap all the airborne particles leaving your residential air particles so pure and clean. This method is considered to be the safest method compared to other methods. It is also notable that mechanical media filters get upgraded efficiency as loading gets on.
Other than these positives, it can be so expensive since it requires frequent replacements after a shorter use. Also, the pollutants disposed of may well cause secondary pollution.
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2. Ultraviolet Germicidal Irradiation
This type of technology works by reducing the number of airborne micro-organisms. They use ultraviolet lamps to kill and deactivate bacteria, viruses, and other harmful organisms in the air. Better still, these low-pressure lamps are well designed to penetrate through the outer structures of the micro-organisms and destroy them off. To achieve this, you must have a higher lighting power and longer exposure time.
There are two types of UVGI filters. One is designed for airstream disinfection while the other is made for surface disinfection. Both work to get rid of those harmful organisms that cause airborne diseases. However, in surface disinfection, they are installed in mostly handles devices to limit the growth of these micro-organisms. Also, surface disinfection is well known that destroy more of these airborne organisms compared to airstream disinfection because the latter has a shorter exposure time.
You can as well install them as portable air purifiers or HVAC systems depending on your needs. Though some mold and bacteria spores are resistant to UV radiation and therefore all you need to do is to expose them for a longer period and increase lighting power. This technology is ideal for inactivating microbes found on cooling coils and any other surfaces. Also, with high intensity, this method can be very effective.
For the disadvantages, with lamps that are uncoated, there is a high possibility that it will develop ozone. Secondly, it puts you at high risk of eye injury. It is inactive yet it doesn’t get rid of microbes. Lastly, it requires high electrical power.
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3. Intentional Ozone generators
This should never be used on occupied spaces. They are typically designed to control any weird odors nearby leaving the air around you as pure as possible. The electrical discharge and UV lamps work by emitting ozone that reacts with other chemical components to kill any biological pollutants. It is greatly advisable to use it in open spaces because ozone can cause lung irritation and its reactions can cause some harmful effects. Even if you maintain it below the public health recommendations, its chemical reactions produce corrosive and irritating effects that can be harmful to your health.
Most of these ozone generators sold as air purifiers use UV light or corona discharge to produce ozone which is dispersed by a fan into occupied space. The best thing about this technology is the fact that it neutralizes all kinds of indoor gases available. It reacts with most chemical components around and can therefore be harmful as well. Any volatile organic compounds and gases can be easily broken using this technology.
Also, its byproducts can damage your wiring, building materials, furnishes, and many other things in your house. This is why it is never recommended to use it in occupied spaces. Something else to note, this technology can lead to the degradation of home materials and also has greater ozone production rates.
These air cleaners work by using a high voltage discharge to ionize any harmful gases around. They break their chemical Bond and completely altering their structures. Using high voltage and high current, the thermal plasma air cleaners generate a high-temperature plasma flame to break down all the gases in your surroundings.
On the other hand, the non-thermal plasma air cleaners speed up the electrons to produce reactive radicals that can easily deactivate and kill and harmful micro-organisms. In addition, these air cleaners have high removal efficiency for some particles and gases to destroy any harmful airborne particles. However, it is well known to form some harmful products that cause health problems. These harmful byproducts include carbon monoxide, ozone, formaldehyde, and many more.
Also, plasma emitted to indoor air contains some harmful ozone and oxygen species that are harmful to human beings. You can as well combine air cleaner with other air cleaning technologies for better air purification results. Finally, plasma is well known for its high filtration efficiency using electrical arcs to keep your air clean at all times. Also, it does not destroy the particle pollutant as compared to gas pollutants.
Just like the above technologies, plasma also comes with a few disadvantages. First, the countless plasma variety generation creates confusion on how it works. Next is the fact that the byproducts are developed by several plasma technologies like chloroform, ozone, nitrogen oxide, particles, etc. What’s more, many studies have researched gaseous clearance with lesser having studied particle removal.
5. Photocatalytic Oxidation
This technology makes use of a high surface area medium that is coated with a catalyst to adsorb any pollutants in the air. When irradiated with UV light a reaction occurs where hydroxyl components are formed on the surface of the media. This reaction is positive since it converts any organic pollutants into water and carbon IV oxide. They convert any gaseous pollutants into the surrounding. However, they are very effective when it comes to converting indoor air. Also, these air cleaners are well known to produce harmful byproducts such as formaldehyde, carbon monoxide, and so on. When used with a UV-C lamp that lacks a coating, it produces harmful ozone.
Ideally, some of these air-cleaning devices will also use adsorbent media to adsorb the generated byproducts. Their efficiency greatly depends on the amount of contact, amount of catalyst, and amount of UV light present on the media surface. Without considering these factors, this air cleaning device may fail to deactivate all the pollutants and instead activate irritations. Through various studies, this method has been proven to remove low amounts of contaminants present in indoor residences.
6. Electrostatic precipitators
These air-cleaning devices have oppositely charged plates on the inside which trap incoming particles that are charged by a high voltage wire. They are highly efficient since they are well known to trap even the smallest airborne contaminants present in the air. With a single pass, it can deactivate up to 60 percent of the contaminants. Depending on the airflow rate, this percentage can increase up to 90 making it one of the best air cleaning technology. As the plates become heavily loaded, their efficiency decreases.
Additionally, particles have different compositions, therefore, affecting their deactivation. These particles also have varied electrical properties that will in turn affect the ability of the plates to hold a charge. Better still, they accumulate dust particles that are a nuisance to most households. Although they remove smaller particles they are not efficient in removing odors and gases.
They can as well increase ozone concentrations in the air making it harmful to human health. Ozone reacts with some chemicals to produce some harmful byproducts. They react with various indoor sources such as carpets, air fresheners, linoleum, polishes, paints, deodorizers, cleaning products, and many more. You can install them as portable devices or in HVAC systems.
Just like Electrostatic precipitators, ionizers use powered electronic processes to charge any contaminants. They use high voltage carbon or wire to charge air particles which in turn produces negative ions to attract any airborne molecules. The charged particles can attach themselves to different surfaces such as furniture or walls.
Additionally, you can install this unit on tabletops, ceilings, or portable air-cleaning units. Since ionizers do not make use of fans to move air particles past the cleaner, it is well known to have low CADRs for air particles. For soiled room surfaces, these ionizers deposit the particles in the floor or walls that can be easily redistributed by touching these surfaces. It is also known to collect dust particles most especially if you are leaving next to busy roads.
Although it removes smaller particles, it does not work best when it comes to odors and gases. Since it uses high voltage to create ionized fields, it can produce ozone as well. This ozone is produced as either a byproduct or a by design and can be harmful to your health. It can cause lung irritation posing as a health risk in enclosed surroundings. Also, this type can generate ozone plus it has low effectiveness since it uses low CARDs.
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8. Adsorbent Media
Adsorption is essentially a process that gets rid of toxic gases by making airflow via an absorbent medium like activated carbon. This medium can be designed to discriminately get rid of some types of molecules as it allows some to pass through. In this circumstance, absorbent medium catches VOCs and CO2 and allows friendlier molecules of air to pass through, such as nitrogen and oxygen.
When used in commercial vents, these cleaners purify the air that is in the building already as opposed to allowing a large quantity of air to adulterate contaminants. With such an approach, the needed air for ventilation from outside is reduced, thus lowering the associated cooling and heating energy loads. This media is suitable for efficient removal of gaseous pollutants plus there is no byproduct created as a result of the process.
The major disadvantage with this option is the fact that you’ll require to do occasional replacement because the power of the trapper becomes low over time. Also, the efficiency isn’t to the best level. What’s more, the adsorption process is reversible: by that, we mean that it can’t be permanently trapped, as such you won’t get long-lasting results.
9. Chemisorbant Media
Chemisorbant media is designed to offer an amplified oxidation potential. It shows a greater working strength for wide-spectrum pollutants in areas where the initiator is undefined: off-gassing waste products from surrounding and processes, general odor control, and outdoor air scrubbing.
Chemisorbant is known to remove formaldehyde (CH2O), nitric oxide (NO), sulfur dioxide (SO2), and hydrogen sulfide (H2S). Such media is created from a mixture of other binders and activated alumina together with permanganate of potash, thus offering maximum adsorption, oxidation, and absorption of an array of gaseous contaminants. The main target indoor air pollutants are gaseous substances. The advantage of this media is the fact that it is an irreversible process – all contaminants are permanently trapped.
The caveat with this process is the fact that you’ll need to do replacement more often since the capacity to trap pollutants diminishes over time. Also, the effectiveness of most consumer-class units isn’t known. Further, excessive pressure falls on sorbent media filters may impact HVAC systems negatively. Aside from that, varying removal efficiency for various gases at varying concentrations. Finally, the standard test ways are not popularly used.