filter vs filterless air purifiers

Filterless vs Filter Air Purifier – Everything You Need To Know

filter vs filterless air purifiers

If you are confused or just want more detailed information before choosing between a filterless or filter air purifier, you have come to the right place. I had exactly the same question when I was deciding on which air purifier to get and in this post, I share all the information that helped me make a good decision about this.

In summary, how do filterless and filter air purifiers compare? When looking at filter vs filterless air purifiers, neither is better than the other.  In as much as filterless air purifiers can generally cover a greater room area than filter purifiers, the decision between the two largely depends on the scenario in which air contaminants need to be eliminated. 

So, without taking too much of your time, I will start by showing and explaining to you about the different types of filterless air purifiers and filter air purifiers. Next I will show you the different scenarios where filterless purifiers will serve you better than filter air purifiers and vice versa. This should enable you to confidently determine whether a filter or no filter air purifier will work for your situation.

The Basics of Filterless Air Purifiers

As you might have seen, filterless air purifiers come in different shapes and sizes. You can get portable ones to use on the go or ones for indoor use.  The main types of filterless air purifiers include ionic air purifiers, photocatalytic oxidation (PCO) air purifiers, ozone air purifiers and ultraviolet light (UV) air purifiers. Out of these, the main ones you are likely to come across are the Ionic and PCO purifiers and I focus on these two here. I won’t waste time discussing every single one of them as I have talked about them a lot in my other blog posts.

Ionic Air Purifiers

There are two popular types of ionic air purifiers and these are called electrostatic precipitators and ionizers. Electrostatic precipitators work by electrically charging metal plates and wire pins placed within the purifier device to create an electrostatic airfield packed with ions that clean the air of contaminants as the air passes through the device.

Also as air is sucked into the air purifier using a fan, the metal plates carrying an electrical charge inside the device attract air contaminants from the air once they react with the ions emitted by the wires.  This way the contaminants do not escape back into the air from the system.

Ionizers or negative ion generators work similarly to the electrostatic precipitators but they are an open system without charged plates to trap contaminants. Just like the wires in the electrostatic air purifier, they only emit negative ions and these are emitted into the air to clump on to positively charged contaminant particles in your homes air. Once clumped up the negative ions make the airborne contaminant particles too heavy to float in the air and eventually the particles settle and stick to surfaces around your home. Ionic air purifiers are able to reduce air contaminants like allergens, dust and bacteria.

PCO Air Purifiers

Unlike ionizers, PCO purifiers clean the air by reflecting and concentrating an intense light on a metal surface which in turn oxidizes toxins in the air that are sucked into the device using a fan. PCO technology was invented by NASA to provide clean air for astronauts in space. The process PCO air purifiers use to clean air is called photocatalysis. It is defined as the acceleration of a photoreaction in the presence of a catalyst.

Photocatalysis uses broad-spectrum UV light which reacts with a thin film of titanium dioxide that, in the presence of water, creates hydroxyl radicals and super-oxide ions that "burn"  harmful air particulates, volatile organic compounds (VOCs) and microorganisms absorbed on the catalyst's surface. Because of the use of UV, many people confuse PCO purifiers with UV purifiers but they are different in that PCO uses additional wavelengths of UV which accelerate the decomposition of air contaminants.

If you are confused by all this, then just know that PCO technology is as good as it gets when it comes to filterless air purifiers. They are able to destroy particles as small as 0.001 microns and this includes pretty much all types of air contaminants including odor causing chemicals while Ultraviolet air purifiers only deal germs and bacteria.

The Basics Of Filter Air Purifiers

In my opinion, filter-based air purifiers are quite straightforward in the way the work when compared to the filterless type. They all have some kind of fan that sucks air into their core, through some kind of material that prevents contaminants from passing through and traps them within the air purifier and then out comes clean filtered air from the purifier. The main types of filter based purifiers on my radar, include HEPA air purifiers, activated carbon air purifiers, biotech air purifiers and Electret air purifiers.

Electret Filter Air Purifiers

If you get an electret air purifier you will see that they use the same principle as ionic air purifiers in the that the attract particles using ions. However they fit under filter air purifiers category as the material creating the charge within the device is a porous synthetic fiber which essentially does not allow contaminants to pass through just like normal air filters do.

Activate Carbon Air Purifiers

Activated carbon air purifiers work by absorption. They are very good at absorbing gases, and VOCs on a molecular basis and do well with odors but you will find they fail dismally when it comes to filtering out larger particles such as pollen and dust.

HEPA Air Purifiers

When you come across HEPA air purifiers, you will eventually see they are categorized as HEPA-Type and true HEPA air purifiers. HEPA-Type purifiers are not as efficient and are actually dumbed down versions of the original HEPA purifier.

So what happened was, when too many HEPA-Type air purifiers started getting on the market, the guys producing the real deal were not happy that they were competing with a substandard product and they ended up creating a standard called true HEPA to distinguish themselves from the dumbed-down bunch.

So if you are serious about getting your air clean using HEPA air purifiers, make sure you go for a true HEPA air purifier. HEPA air purifiers clean air by trapping contaminants in a paper-like filter material that's packed in the device in a zig-zag accordion-like manner.  This provides a large surface area for air to be pushed through by a suction fan and allows for an optimal number of pollutants to be trapped. HEPA air purifiers make the air in a room cleaner and cleaner the more times the same air passes through the device.

HEPA air purifiers can remove pollutant particle sizes as small as 0.1 microns from you air but normally they are designed to deal with larger particles of 0.3 microns. They are good with most pollutants and particulates but they struggle to remove odors, chemicals or gasses.

Biotech Air Purifiers

Finally, in the filter air purifier category, we have biotech air purifiers. You will rarely come across these types of air purifiers as not much development has been done for this technology in the past 30 years or so. Biotech air purifiers work by using microorganisms to remove air pollution. Simply put, either with a fan or through convection, they suck air into their filtration core which contains microorganism that digest and turn air pollutants into water, base elements and carbon dioxide.

The system works by microorganisms oxidizing dangerous pollutants in a filter system known as a bioreactor. This technology allows for the capture and destruction of all the contaminants in the air with no limitations on their type or size and the result is cleaner air without the problem of waste disposal.

Biotech air purifiers can remove ultrafine particulate matter, VOCs, odors, hazardous air pollutants (HAPs), and much more but such devices are a rare and expensive and the only one I know available to consumers is provided by U-Earth and the process of getting one from them is tedious.

Should You Get A Filterless Or Filter Air Purifier?

Now that you know the difference and understand how the different filter and filterless air purifiers work we can get into the real reason you are here. Which one is better for you? Well, I found 8 key situational factors that will help you confidently determine this.

The main factors to consider when considering Filter vs Filterless purifiers include,

  1. What contaminants you want to remove from the air in your house 
  2. Your room size and location of your air purifier
  3. How often you are willing to maintain the device
  4. Noise level
  5. Energy consumption
  6. Your tolerance to by-products of air purification,
  7. Your need for style and design
  8. The price

What contaminants you want to remove from the air in your house

This is probably the most important make or break factor when choosing between filter and no filter air purifiers. If you have read carefully through my explanations on the basics of filter and filterless air purifiers you will find that some purifiers are only good at removing certain air pollutants.

You could be trying to remove pet dander, dust or traffic pollution from your air, or trying to address smoke and odors or simply airborne germs and bacteria. If your challenge is specifically contaminants like pet dander, pollen, or dust then a filter air purifier and more particularly, a true HEPA purifier would do the job for you.

If you also want to get rid of odors beyond particulates, you can also consider a true HEPA purifier but it has to be combined with an activated carbon filter. HEPA air purifiers are recommended for getting rid of air pollutants that cause allergies and asthma and they are accordingly used in hospitals and aeroplanes.

Ionic air purifiers are also used in hospitals as they deal well with viruses and bacteria. Unlike HEPA purifiers, they can also remove particulate matter but they are just not as good as HEPA purifiers in dealing with pollen and dust and their effectiveness in removing pollutants quickly wears off as contaminants attach to their metal plates. They are also poor at dealing with odors.

Now, if your worry is removing every single pollutant you possibly can from your indoor air then the best approach is to get a PCO or Biotech air purifier. PCO purifiers will remove all contaminants in the air of up to 0.001 microns (very very small)  while Biotech purifiers can reach 0.003 microns. This is stark, compared to 0.3 microns by ionic and 0.1 by HEPA purifiers. However, the catch is that these devices come in at considerably higher prices.

So taking account of what the various filter and filterless purifiers remove, I would suggest going for a HEPA purifier if your problem is mainly pet dander, pollen, dust, traffic pollution and you don’t really care about odors. If you are concerned about bacteria and influenza, then you can consider an ionic air purifier. Finally, if you want totally clean air and an all-round solution, only then should you go for a PCO air purifier. I would avoid a biotech purifier as its a rare device and it is not as readily available.

My final thoughts when it comes to removing contaminants are to go with a true HEPA purifier combined with a carbon activated filter. This will give you greater long-term performance than an ionic purifier. But if you  are not on a budget, definitely go for a good PCO air purifier. So in the case of removing air contaminants, filter (HEPA) air purifiers are better than filterless air purifiers for reasonably priced devices and when money is not a factor then filterless (i.e PCO)  technology is the way to go. I discuss what things air purifiers can get rid of from the air extensively in this post here, if you would like to know more.

Your Room Size and Location of Your Purifier

Room coverage is where ionic air purifiers do a much better job than true HEPA purifiers.  This is largely due to the mechanical nature of filter air purifiers. Ionic air purifiers can cover rooms of up to 3500 sq ft effectively while true HEPA purifiers start to lose their effectiveness at around 1000 sq ft. As for PCO purifiers, I have seen devices that claim to do any room size in a large estate type home, so room size is not a problem for PCO technology in a home or most office settings.  

So in the case of room size, go with a filter air purifier if the space you want to cover is less than 1000 sq ft but any larger then you would rather go filterless. With this in mind, if you are getting an air purifier for your desk at work or in your home office, then a true HEPA purifier (filtered) is your best bet.

However, if you are on the move in your car, rather go for an ionic or PCO air purifier as you are constantly reintroducing new air into your car as you open and close your doors and windows and this can see you spending a fortune on filters if you use a filter based air purifier. That said, if you go the ionic route, make sure your ionic purifier has some kind of dust collecting unit, to avoid the neutralized contaminants settling on surfaces around your car.

How Often you are Willing to Maintain the Device

This can really be a make or break for a lot of people. If you go the filter air purifier route, be ready to change your filters often. This means you have to be financially prepared to replace filters and you also have to make sure you get a device that you can easily find replacement parts for. That said, some filters are washable and can be reused but the fact remains that you have to take out a filter and put it back into your device quite often.

With filterless air purifiers, if you go the ionic route, you constantly have to wash the wires and metal plates for them to remain effective. This means you don’t pay anything for maintenance, however you still spend a lot of time maintaining your device.

On the other hand, if you go the PCO route, your device can work for more than 3 years without maintenance. Then when it comes to maintaining your device, all you need to do is replace a bulb. For me, this is a small price to pay compared to constant cleaning or yearly replacement of parts. That said, my verdict on maintenance is that if you don’t mind the hustle of replacing parts go the filter route.

Noise Level

When it comes to noise, filter air purifiers are much nosier than filterless air purifiers. This is because filter air purifiers use fans to pull and push air through their filter. If you put the quietest filter and filterless air purifier side by side, the filterless purifier will win hands down.

That said, some filterless air purfiers, especially PCO type purifiers actually have fans and will have a quiet humming noise. So if silence is what you are after, go for a fan-less ionic purifier that uses convection and electrostatic attraction to trap air contaminants.   

Energy Consumption

When it comes to energy consumption, filterless air purifiers perform better than filter air purifiers. The most energy efficient purifiers are UV and PCO air purifiers. But please make sure that if you are basing your decision on energy consumption levels that you do not sacrifice the performance of the device in removing air contaminants. This is generally a negligible factor for home air purifiers but if you concerned about energy, in the long term I think you will save the most with PCO air purifiers without losing out on performance.

Your Tolerance To By-products Of Air Purification

All air purifiers produce by-products but the question is whether they release them in the air or not. Filter air purifiers collect the by-products of their purification  process on their filter. The only time they become dangerous is during filter replacement as any false move could reintroduce the the trapped contaminants back in the air. The exception here is with Biotech filters, which actually destroy the contaminants.

As for no filter air purifiers, they release their by-products into the air. The worst are ionic air purifiers. They release ozone into the air, which can flare up all kinds of respiratory problems especially for people with preexisting conditions like asthma. Ionic air purifiers without collection units also leave thin layers of dust on surfaces as the contaminants they neutralize are just left to settle anywhere and have to be cleaned afterwards.

The situation is better with PCO air purifiers. Most PCO air purifiers will emit ozone to some extent but there are devices that don’t emit any at all. So when it comes to by-products, PCO purifiers are your safest bet.

In view of all the different by-products produced, my take is to avoid ionic air purifiers if you, your pets or anyone in your family is sensitive to ozone or has any allergy issues. Rather go the filter route as you have more control over the by-products or look for a PCO device that emits no ozone.

Your Need For Style And Design

When it comes to style and design, your options are more limited for filterless air purifiers, most especially ionic purifiers. You will mostly come across thin, vertical corner units or small, compact square units. They usually look like something out of a space and can only be placed on the ground or on a table top. Its a rare find if you see a mountable one. That said, I have seen more style with PCO purifiers but they are also limited in variety, as there are not that many companies manufacturing them.

On the other hand, filter air purifiers come in all shapes, sizes and colors. You can more easily find a product that matches your decor and place devices practically anywhere inside your home or business as some devices are mountable. So if on top of health benefits, you care about style, you are sure to find something more suitable with filter air purifiers.

The Price

Finally, though I think the price in itself is not exactly a determining factor, the performance you get for your money from the different devices is a deal breaker for me. Now, all the filterless and filter technologies I have mentioned, have prices varying from as low as US$50 - US$2000 for a mobile home unit. But from my observation, you start to get the most effective devices in the US$300 - US$1000 range.

PCO purifiers are upwards of US$600 brand new while HEPA and Ionic purifiers are spread across the range. So in my opinion, if you are going to go for a device that's priced over US$600, then go for a PCO purifier. If your room size is within 1000 sq ft, then go for a good HEPA purifier under US$600 and only when you have a larger room or you need a device for your car and you have less than US$600, should you go for an ionic air purifier.

The most important thing here is to get the most value for your money and from my observation, the rule of thumb I have given you above should keep you within the most optimal value you will get for your money between no filter and filter air purifiers.

Final Thoughts

This was a long post and well done if you managed to get through it all. You now have a good understanding of the nuances between filterless and filter air purifiers. However, if you find yourself still confused or did not manage to get through everything here is the most important thing to know when looking at no filter vs filter air purifiers:

There are various technologies under the filter and no filter purifier categories and it is not as simple as saying one is better than the other. In view of this, for a number of reasons, PCO air purifiers are the best filterless technology while true HEPA purifiers are the best filter technology . When the two are compared,  PCO purifiers generally perform better and you can safely conclude that filterless air purifiers are better than filter air purifiers.

Through careful observation, this is the conclusion I have arrived at in my experience with air purifiers but if you beg to differ please do share thoughts in the comments below and I am open to debate. Also, feel free to ask me any questions if you are confused about anything regarding air purifiers.

About the Author


Jean is a research economist by profession and he runs Fresh Air Genie. He is enthusiastic about maintaining good air quality at home and on the go and he shares his knowledge about this here at Fresh Air Genie.


    1. Author

      Hello Chris. The Airsoap is an ultraviolet light device. This is great for germs/bacteria/viruses and other organic pollutants as it literally burns them. However, they are not so good for all particulate matter and other gases and odors. You almost always need a combination of filtration systems to clean your air well. If it’s organic particulates you are worried about, the Airsoap is a great air purifier.

  1. Thank you! This was very well written and of information that is easy to understand. You helped me a lot……thanks again

  2. Hello Jean-Baptiste

    What do you think about: Airfree P3000 Filterless Air Purifier – Air free Home Air Purifier Requires No Filter, Fan, or Humidifier.
    Thank you,

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