When you finally decide to get an air purifier, you might find yourself faced with the daunting task of deciding which type you should get. Over my experience with air purifiers, I have come across quite a number of air purifier technologies and each of these technologies comes in different varieties. I have seen a lot of air purifiers and I am tempted to say I have seen them all and so in this post, I will show you every single type there probably is out here.
In short, what are the different types of air purifiers? There are about 17 distinct types of air purifiers on the market today. The five most common of these, include HEPA, Ionic, Photocatalytic Oxidation (PCO), Adsorbent and Revitalizer or Water Air Purifiers. Each of the 17 varieties can be designed as either portable mobile air purifiers or fixed room air purifiers.
Its important to define what an air purifier is to better understand the different types that are out there. An air purifier is a device or product that is specifically designed to improve air quality by getting rid of pollutants in the air.
When I examine all the different types of air purifiers I have come across, I find some release particles into the air to react with and neutralize or destroy air contaminant, while some suck or draw air within themselves and either trap, adsorb or destroy contaminants contained in the air they draw in.
These different ways each air purifier deals with air contaminants can be classified into two categories of air purifiers namely active and passive air purifiers.
The active air purifiers are active in the sense that they release particles to chase after and neutralize floating particles. On the other hand, passive air purifiers are classified as passive because they wait for the air to be exposed to their cleaning unit or media before they can get rid of contaminants in this air thereof.
The different types of air purifiers can be further classified into filter and filterless air purifiers. Of the 17 types of Air Purifiers that exist as at the time of writing this post (Jan 2019) the active air purifiers include,
- Ionic air purifiers
- Spray air purifiers and
- Ozone air purifiers
The passive air purifiers include,
- UV light
- Air scrubbers
- Charged Media
- Other types of filter
- Air-to-Air Exchangers
- Air Curtains and
- Thermodynamic Sterilization
For each of these, I give you a full description of how they work and what they are able to remove from the air. Thereafter I talk about whole house air purifiers and personal air purifiers which are the two main secondary forms that some of these air purifiers take besides the standard room air purifiers.
Lastly, I talk about plants which in my opinion really do not qualify as a type of air purifier but I have seen some people mention plants when listing the different types of air purifiers so I thought I might as well clarify how they purify the air though they are not essentially a type of air purifier.
To kick start the list, let's I will start with HEPA air purifiers. Below is a navigation table for you to get around quickly as this post is quite long due to the level of detail i provide.
1. HEPA Air Purifiers
I believe HEPA air purifiers are by far the most popular and common type of air purifier out there. HEPA stands for High Efficient Particulate Air filter and air purifiers that contain this kind of air filter are called HEPA air purifiers.
HEPA air purifier filters are fiber-like material with very tiny holes placed strategically within a device to act as a sieve and hold back air pollutants that are bigger than these holes.
When in action HEPA air purifiers work by sucking air within themselves and through their filter and then blowing the sucked air out the device thereafter. As the air passes through the filter pollutant particles are trapped through a mechanism of interception and impaction and the air comes out of the purifier fresher than it was when it entered.
The more air passes through the purifier the cleaner it gets. HEPA filters are designed to trap pollutant air particulates that are as small as 0.1 microns. These are particles that are too small for the human eye to see. They include stuff like ultra-fine dust and dust mite allergens.
To keep a HEPA air purifier performing at its best performance you have to change filters often or as instructed by your devices user manual. HEPA filters can last anywhere from a month to 4 years depending on their design and usage.
HEPA air purifiers are very effective with mold, mildew, dust and other ultra-fine to large particles but unfortunately, they can't get rid of gas and odor molecules as these fall under 0.1 microns and are too small. To get the best of HEPA air purifiers always go for true HEPA devices rather than other types of HEPA.
You will often find devices labeled HEPA-type and these are just not as effective as true HEPA for particulates. I would stick to a HEPA air purifier if I am not trying to get rid of bad smells toxic gas or Volatile Organic Compounds and my main concern was airborne particulate matter like dust, pollen or soot from traffic pollution.
2. Other Types of Filter Air Purifiers
Besides purifiers with HEPA air filters, you also get air purifiers made of polyester pleated filters, washable filters, and fiberglass filters. These filters act as air purifiers either by making up part of a device that sucks air out of a room through its cleaning core or simply by acting as a barrier preventing airborne pollutants from outdoors from entering into your home or between rooms in your home.
These other filter media may not be as effective as HEPA filters contained within the core of an air purifier device that sucks air but they actually work out to be more cost effective depending on what you are trying to filter out of your air. For instance, HEPA air purifiers don't do well with moist air. So if you are using one when vaping you will find your filter wears out faster and you have to replace it often due to moisture.
This is one instance where other types of filter air purifiers besides HEPA purifiers come in and play an important role. Besides being used on their own they can also be added to other types of air purifiers including HEPA purifiers to serve as prefilters and shield other purification technologies contained in a device from moisture.
The other types of filters are also used on many purifiers as prefilters for bigger air particles and allow the main filters or air cleaning unit to last longer and only deal with much finer particles. To add on, you also get bigger filters for bigger air pollutants like flying insects (yes insects are pollutants). A good example of insect filters you can put on doors and windows is the Magic Mesh filter which will let air into your home while keeping bugs out.
Due to various limitations of HEPA filters, the other types of air filters are mostly used as standalone filters on air vents, in air ducts, and under windows as window air filters. Some of these filters come combined with baking powder or activated carbon to filter odors and gases out from your home as such molecules are too small for them on their own.
3. UV Light Air Purifiers
The next type of air purifiers are Ultraviolet light air purifiers. These use ultraviolet light radiation to destroy air contaminants. They draw air in within a compartment of devices that contains the UV light and air contaminants get destroyed as they are exposed to the light.
The problem with UV light air purifiers, however, is that they only work for microorganisms. They do well with viruses, bacteria and germs but are useless for particulates. Almost always it is better to get a UV air purifier that comes as part of a HEPA air purifier or some other kind of filter air purifier depending on what you are trying to clear out from your air.
If you get a UV air purifier, be sure to check on the lamps or bulbs often and replace them as instructed in your devices user manual. Also be careful with UV because it can emit small quantities of ozone which can be harmful to people in your home who have respiratory conditions if inhaled.
4. Photocatalytic Oxidation (PCO) Air Purifiers
Like UV purifiers PCO purifiers are filterless. They however use broad-spectrum UV light in a reaction chamber to cause a reaction with water moisture and a thin sheet of a metal catalyst such as titanium dioxide that creates super-oxides and hydroxyl radicals that burn air contaminants. In this reaction, PCO air purifiers destroy air pollutants that get exposed and absorbed on the surface of the thin metal catalyst film of the air purifiers reaction chamber.
All this happens as the air purifier circulates air in and out through its reaction chamber core using an internal fan. PCO air purifiers will incinerate every air contaminant, from gases to particulates, VOCs and microorganisms as small as 0.001 microns. 100 times smaller than what HEPA air purifiers can get rid of.
It used to be that PCO air purifiers produce ozone but you can now find some that do not and only produce water and carbon dioxide as by-products. PCO air purifiers are also low maintenance and you only need to replace your reaction chamber about every 2-3 years and wipe the device as you would other appliances in your home to keep it clean.
For those of us from the 80s and 90s replacing the reaction chamber is as easy as placing a cassette in a radio or VCR (if you remember how to do that). For PCO air purifiers I swear by the Airocide air purifier.
5. Photo Electrochemical Oxidation (PECO) Air Purifiers
PECO air purifiers work just like PCO air purifiers and are just an advanced version of PCO. Instead of a thin film of titanium, PECO air purifiers have a filter membrane coated with some nanoparticles that cause a more powerful and faster oxidation reaction than PCO air purifiers when exposed to broad-spectrum UV light.
Tests show that PECO air purifiers are able to destroy every single kind of air contaminant just like PCO purifiers and they destroy contaminants more than 50% faster than any PCO air purifier over any given time period. The challenge with PECO purifiers though is that you have to replace their filters every year and this could happen more often in a year depending on how polluted your indoor air is.
If you don't mind frequent filter replacements and all you care about is the best air quality then perhaps the PECO air purifiers could just be for you. That said the only PECO air purifier I am aware of at the moment is the Molekule air purifier.
It's damn expensive and all the real user reviews I have seen about it are not encouraging so I don't have any ambitions of trying it. I also don't recommend it and I would avoid it until a better device is available, and peoples general experience with this device improve as the technology becomes more widespread.
6. Adsorbent Air Purifiers
Adsorbents are materials that naturally absorbs gaseous pollutants and moisture in the air. Some good examples that are used for air purification include volcanic rock minerals, activated carbon, soda or baking powder.
The most common I have seen used in an electricity-powered air purifier that has a filter that contains activated carbon. Like all adsorbents activated carbon does a great job at absorbing gases and odors which other air filters and some air purifiers simply can't do.
Activated carbon is thereby commonly combined with HEPA or electrostatic air purifiers to give them the added benefit of absorbing and removing gases and odor from the air.
Other adsorbents air purifiers are either just containers or bags containing the adsorbent and are used purely for getting rid of odors, gases, and moisture. Some great examples of this you can check out are the Bad Air Sponge or bamboo charcoal bags like the MOSO air purifier bag.
7. Spray Air Purifiers
A very cost effective alternative air purifier to mechanical air purifiers, especially if it's for short term use is to an air-purifying spray or air sanitizer like Ozium. Ozium contains some cleaning agents like trimethylene and propylene glycol that attack microorganisms and neutralize gases and odors in the air.
For a good reason, Ozium has a reputation as a secret weapon for a lot of weed smokers. You should keep Ozium for emergency situations where you need to get rid of smells quickly in your home like when visitors are coming and someone dropped a stink bomb just before they arrived.
You can also use it as a substitute for air freshener in a smelly loo as is does more than just mask smells and actually destroys odor molecules.
8. Revitalizer/Water Air Purifiers
Water air purifiers do not work like your typical mechanical air purifier. They use water as a filtration system and literally wash air pollutants out of the air. What happens is that they suck air into their cleaning compartment using a fan like all other air purifiers do and then they pass this air through water that's being bubbled around and stirred up by some kind of vibrating rod.
The water in the device then absorbs some pollutants and thereafter releases the air back into your home in the form of water vapor or mist just like a humidifier. In fact part of the revitalizer uses the exact same technology humidifiers use to create the mist they release into the air.
What’s more, you can add some scents and cleaning agents to your water which make your home’s air smell better by reacting with gases and eliminating odors.
Water air purifiers can remove, particulate contaminants like dust and pollen and also odors, from the air and using an antibacterial solution can also get rid of bacteria in the air. They are also cost-effective in terms of maintenance as you only need water for them to get rid of contaminants and purify your air.
However, they do increase humidity in your home and can create a conducive environment for mold and dust mite if you are not careful. Their ability to filter out gases and VOCs is also questionable.
9. Air Scrubbers
Air scrubbers are heavy duty air purifiers which are usually used for industrial and commercial purposes. They come in two forms, wet scrubbers, and dry scrubbers. Wet scrubbers clean the air in a similar way as air revitalizers do but more intensively.
Air is drawn into the air purifier and exposed to a scrubbing liquid in a water tank section of the purifier. This liquid then washes corrosive air pollutants, heavy particulates, and smelly gases and the rest of the air is moved through another filter and an activated carbon bed to get rid of VOCs and any remaining contaminants that the cleaning liquid failed to get rid of.
The dry scrubber does not contain any liquid or compartment to wash air. It works just like an ordinary activated carbon HEPA air purifier but cleans air more intensively using faster fans and air recirculation rates and much bigger filters. Air scrubbers are normally used by construction workers to improve air quality in a building once a job is complete or prevent air pollution between rooms during renovations.
They are also used in factories to prevent pollution from various manufacturing processes. You can get smaller industrial versions for use in your home but it better to hire one or to hire a professional cleaning service if you ever need to use one. Air scrubbers can come in handy if you need to get rid mold or you want to improve the air quality in your basement or crawl space, especially after flood damage.
10. Ionic Air Purifiers
Ionic air purifiers are also known as negative ion generators or ionizers. They work to remove air contaminants by using an electrical charge to produce negative ions which are then released in the air. These ions then react with positively charged pollutants in the air and neutralize them causing them to fall to the ground as they become too heavy to stay suspended in the air once neutralized.
The negative ions balance the electrical charge in your home resulting in clean air. Ionizers are great at dealing with germs, bacteria, and viruses and also do well with pollen, dust and other particulates in the air. They are however limited when it comes to dealing with gases and odors. Ionic air purifiers can only remove particles of 10 microns and more.
Compared to other types of air purifiers ionizers usually take much longer to improve air quality. Furthermore, when the metal rods in the air purifier that produce negative ions become dirty by attracting positively charged contaminants to themselves ionizers quickly become ineffective in producing ions.
Moreover, over time, they result in a build-up of thin films of neutralized particles on surfaces and walls around your house. With time you will see your ceilings and walls also starting to lose color if you use your ionizer long enough.
Lastly, most ionizers produce ozone which is a harmful irritant for humans and animals. Though the quantities they produce are small, if you have anyone with a weak immune system or respiratory problems in your household, even small amounts of ozone can make them sick.
11. Electrostatic Precipitator Air Purifiers
Like ionic air purifiers, electrostatic air purifiers also use an electrical charge to get rid of air pollutants. They, however, use an electric charge to create negatively charged metal plates within their purification unit which attract positively charged air contaminants out of the air.
The contaminants collect in the air purifier and you have to clean it often because as the metal plates become saturated they become ineffective in attracting particulates.
Like ionic air purifiers electrostatic precipitators also produce ozone but at least they do not create a mess for you to clean up on surfaces around your home. You also don't need to worry about discoloration of walls and furniture as the device does not emit the negative ions that cause this in the air around your home.
12. Ozone Generators
Despite its harmful effects on humans, ozone is a strong oxidizer and cleaning agent and does quite a good job at cleaning the air. It's also the only type of air purifier that can clean air pollutants when they are not airborne and they are settled on surfaces.
Ozone generators clean the air by releasing ozone into the air in your room. As the ozone spreads in and around the air in your room, because it's such an unstable substance it chemically reacts with air pollutants around your room turning them into water molecules, and carbon dioxide but sometimes also other toxic substances.
Ozone has its advantages especially when it comes to dealing with pollutants like dust mite, strong permanent odors, and mold on walls but you have to know how to use it. If you mess around, this stuff can easily kill small pets, like cats, birds, rodents, and reptiles. In small quantities, ozone can cause you chest pains, and make breathing difficult. In large quantities, it causes eye and throat irritations and finally lung damage.
If you really have to use an ozone generator, I strongly suggest calling a professional air cleaning service. If they are good, they will advise you to make sure you, your family and your pets are not at home when they are doing the cleaning with ozone, until at least an hour after they are done.
Professional cleaning services can also do a deep clean of your car with ozone to make it smell brand new again. I can’t stress enough on dangers ozone so stay safe and play by the rules here.
13. Charged Media Air Purifier
This type of air purifier works by using both the mechanisms of filtration and electrostatic air charge to clean your air. A charged media air purifiers consist of an electrically charged thin wire grid operating in conjunction with a filter pad or mat. Most charged media air purifiers come with a fiberglass or cellulose filter pad or similar material through which air is blown.
When your air purifier is on, electricity flows through the wire grid, and an intense electrostatic field is created. Next, air pollutants are drawn into the device by a fan and through this field are polarized and caught by the filter pads just as tiny metal particles catch on to magnets.
Once your filter pad is filled with pollutants, you have to remove it and replace it with a clean one. Through this process, charged media air purifiers can remove particulates sizes of as small as 0.01 microns. Accordingly, just like HEPA air purifiers, they do well with particulates but under perform in filtering odor-causing gases. To filter our odors, you can get a charged media air purifier that comes with an activated carbon filter.
14. BioTech Air Purifiers
Biotechnology air purifiers are probably the newest kid on the block when it comes to air purifiers. They clean the air by using three factors, namely, convection, molecular charge attraction, and natural oxidation. In biotech air purifiers, convection and fans are used to draw large particulate matter of over 0.5 microns like dust and dander into the air purifiers cleaning section, which is called a bioreactor.
Next smaller ultra-fine air pollutants like Hazardous air pollutants (HAPs) and VOCs are drawn into the cleaning unit of the air purifier by a process of molecular attraction. Molecular attraction happens when the air around the air purifiers’ bioreactor which is electrically charged and rendered neutral by "grounding", is used to attract 90% of the particulate contaminants in the air that do not respond to ventilation.
Once the various types of air contaminants are drawn into the bioreactor, activated by a mix of water, oxygen, enzymes, and contaminants an accelerated process of natural oxidation takes place and this digests and the air contaminants breaking them down into water, carbon dioxide and base elements and resulting in clean air being released from the air purifier.
The only biotech based air purifiers I have seen on the market so far are the U-Earth Aircel air purifiers.
15. Air-to-Air Exchangers And Energy Recovery Ventilation
If you have ever asked yourself how to remove the moisture and pollutants in the air while retaining the heated or cooled air in your home? Than an air-to-air heat exchanger is for you. This is quite a complex air purifier and a large device that ensure good air quality and temperatures in your home with minimal waste of energy.
Air exchangers transfer the thermal energy of your indoor air to incoming fresh air, allowing moisture and pollutants to be vented out of your home while retaining the heat. An air-to-air heat exchanger can remove excess humidity and flush out odors and pollutants generated indoors, all with your windows and doors closed.
This type of air purifier comes in very handy if you have air ducts or an HVAC in your home and you are serious about minimizing your heating and cooling energy bill while maintaining the highest air quality in your home. For a deeper explanation of how air-to-air exchangers work check out this article.
16. Air Curtains and Doors
Air curtains and doors don't actually clean air but prevent pollutants from getting in and out of a room by separating a room from other rooms or outdoor air using a strong stream of air blowing downwards from the top of your door to the bottom. It is kind of like an air shield.
The strong stream of air pushing downwards from the top air actually prevents, odors, flying insects and other forms of pollution from moving across spaces even though the door or window between these spaces is wide open.
Air doors also help save energy by reducing heat transfer in and out of a building. You can get one for your home to keep pollution out while keeping your doors and windows open but normally these are used in restaurants, shop entrances and in office kitchens and canteens.
17. Thermodynamic Sterilization (TSS) Air Purifiers
TSS air purifiers use heat sterilization in a ceramic core with micro capillaries. Their ceramic core heats up t o 200 °C (392 °F) and incinerates pollutants. TSS purifier manufacturers claim that this technology can get rid of 99.9% of microorganisms.
TSS purifiers do not filter and trap or remove particles like filter based air purifiers but rather rely on air convection for air to pass through their core and once they clean the air it is immediately cooled using heat transfer plates and released back into your house. TSS purifiers have no known harmful by-products and can reduce the concentration of ozone in your atmosphere.
18. Whole House Air Purifiers
Now that you have a good grasp of the different air purifier technologies we can look at the different types of secondary uses these technologies are applied in. The first of these is whole house air purifiers.
Whole house air purifiers are air purifiers that are normally installed in your air duct or at the inlet of your HVAC system to provide clean air and improve air quality across your entire home. They are large filter based air cleaners.
There are a variety of models out there but they are mostly filter based and they use filters ranging from activated carbon HEPA filters to charged media fiberglass air filters. I discuss whole house air purifiers in more detail here.
19. Personal Air Purifiers
Personal air purifiers are more portable types of purifiers that you can take around with you everywhere you go. The technologies these use vary as widely as the number of different types of air purification technologies does.
Personal air purifiers use all sorts of purification technologies ranging from filters to ionizers to biotech air purifiers. Personal air purifiers include masks, table and desktop air purifiers, travel air purifiers and car purifiers among others. If you are interested in personal air purifiers you can check out my extensive post on different types of personal air purifiers.
20. Plant Air Purifiers
Lastly, on my list of types of air purifiers, we have plant air purifiers. While plants don't have the same air purification strength as you electrical air purifier? Research from NASA has proven they can absorb toxins in the air and naturally and gradually improve your indoor air quality.
Now not all plants will remove air pollutants and some plants will perform better than others for different types of air contaminants. One thing that's for sure though is that plants will not help you with odors, and particulate matter like dust, pollen or pet dander. They are better for gases and VOCs which include substances like formaldehyde, carbon monoxide, and benzene.
Also if you go for plants to improve your air quality, be careful to get plants that are not toxic or poisonous especially if you have pets and kids in your home. Some popular plants for improving air quality include the Spider plant, Dracaenas, and bamboo palms. For more information check out my extensive post on plants that clean the air.
Now that you know about the different types of air purifiers, have a look my specific guide on which brand air purifier to go for if you want the best air quality in your home.