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Filter vs. Filterless Air Purifiers

Air Purifier Filters on the Floor

Air Purifier Filters on the Floor

T here are multiple types of air purifiers to pick from depending on the specific pollutants the systems target, the technologies they use, and so on. Classification is made even according to the presence or absence of filter media, and this is the topic we cover here. In the following, we will look into filter-free air purifiers and systems that rely on filter media in their operation, how both types work, and their pros and cons, helping you become informed on what differentiates them to more easily decide what system complies best with your expectations.

Filterless UV Air Purifier Plugged In Power Outlet

Filterless UV Air Purifier Plugged In Power Outlet

Filterless Air Purifiers

What is a filterless air purifier?
An air purification system that cleans the air by removing allergens and particles that linger in it, all without relying on physical filter media but rather different technologies that serve the same purpose as filters do.

There are two main types of filterless systems to pick from, more precisely ionic purifiers and PCO purifiers, each coming in different shapes and sizes and complying with different needs when it comes to area coverage.

Ionic Air Purifiers

Ionic systems are divided into two categories, specifically ionizers and electrostatic precipitators.

  • Electrostatic precipitator: Use electrically charged metal plates and wire pins to make an electrostatic airfield filled with ions that clean the air as it passes through the system. The metal plates are electrically charged so that they attract the pollutants, ensuring they won’t escape back into the air but rather get trapped inside.
  • Ionizer: Known under the name of negative ion generator, its operation is similar to that of an electrostatic precipitator, the main difference standing in the fact that it won’t trap the contaminants inside. The system actually emits negative ions into the air, which will clump onto the contaminants that are positively charged, causing the particles to become too heavy to float into the air and inevitably drop and stick to surfaces beneath them.


  • Negative ions released into the air can have a beneficial impact on your disposition, making you feel happier and helping you relax.
  • There are no replacements to make as time passes as no filter media is utilized.
  • Do not draw much power to run, which translates to inexpensive operation.
  • The ions that are released flaunt germicidal capabilities, sanitizing the air.


  • Emits ozone by-products into the air, which makes its operation dangerous for asthma sufferers.
  • As the charged particles drop on surfaces, they can get a dusty appearance.

Photocatalytic Oxidation Air Purifiers

Their operation makes PCO technology systems able to destroy particles down to 0.001 microns in size, which means that any air pollutant, contaminant, or microorganisms the system encounters won’t escape.

PCO systems use the process of photocatalysis to work, which is an acceleration of photoreaction when a catalyst is present. The process uses UV light of a broad spectrum that reacts with titanium oxide, creating hydroxyl radicals and ions and basically burn microorganisms, air particulates, and VOCs, obliterating them from the air.


  • Transform the polluting particles and destroy them rather than restoring to trapping them.
  • Eliminates particles as small as 0.01 micrometers present in the air, which makes it more effective than any other air purification system when it comes to tackling ultra-fine particulates.
  • Ability to eliminate toxic gas pollutants from the air, including the likes of benzene and toluene.
  • Able to provide a feat most air filtering systems cannot – destroys nitrous oxide and carbon monoxide.


  • Can produce ozone, a toxic air pollutant. Check the rating to see how much it produces – in case values are large, avoid that specific model.
  • Take a longer amount of time to properly clean the air in the room as opposed to other air purifiers.
Air Purifier Filters on the Floor

Air Purifier Filters on the Floor

Filter Air Purifiers

What is a filter air purifier?
An air purification system that relies on the use of one or multiple filtration media to rid the air indoors of polluting particles and microorganisms that plague it.

These systems are classified according to the main or sole media used in their operation, and the general types you will encounter include HEPA, activated carbon, and electret systems.

HEPA Air Purifiers

Hands down, the most efficient type of air purifier is the one that uses a True HEPA filter in its operation as filters which comply with this high standard are tested and proven to eliminate a minimum of 99.97% of airborne particles down to 0.3, sometimes even 0.1 micrometers in size from the air. Due to their operation, HEPA filters provide the most trustworthy performance when it comes to the removal of asthma and allergy-triggering particles, so if you or a household member suffer from the aforementioned health issues, it’s best to seek out a system that uses this filtration media.

Warning: Beware that there are manufacturers who seek to trick customers into believing the filter media used by their products is up to HEPA standards by using the HEPA-Type rating. While efficient in the removal of contaminants as well, these filters are not up to the aforementioned standards. What you must seek is for the filter to be rated as True HEPA to make sure your money goes toward a system that provides almost complete removal of air polluting particles.


  • Among filter-based air filtration systems, HEPA is the most efficient as its reduction rate is upward of 99.97%.
  • Replacement is required quite rarely as opposed to other filtering media (depending on the model, only once every 2-3 years).
  • Those that are rated as washable or permanent imply that you can clean the HEPA media and reuse it without it dropping in efficiency when it comes to airborne pollutant trapping.
  • Most effective type of system for allergen removal, being recommended by specialists for individuals who suffer from asthma and allergies.
  • Effective trapping of mold spores, when paired with a dehumidification system ensuring that mold growth won’t ever become an issue in your home.


  • Unable to trap odors and gases on its own, needs to be paired with active carbon media to fulfill this task.
  • Even though replacement of the media is required considerably less often, the filters are costlier as opposed to competitors.

Activated Carbon Air Purifiers

The operating method used is absorption, which makes activated carbon filter systems particularly efficient at absorbing and removing odors, gases, and volatile organic compounds from the air. One downside, however, is their inability to tackle larger-size particles like pollen and dust, which is why the filters are mostly used in combination with HEPA media in air purification systems to ensure thorough air cleaning.


  • Highest efficiency when it comes to the reduction of unwanted odors from the air, regardless if the source for the smells is gaseous or chemical in nature.
  • Best at capturing smoke particles from the air, regardless if it is a wildfire or tobacco smoke.
  • Filter media is generally inexpensive to replace, so upkeep costs should not pose an issue.
  • Do not emit by-products, which makes them completely safe to use 24/7, even in nurseries or bedrooms.


  • Cannot trap allergens like dust from the air. It is preferable to pair the system with a HEPA filter if you want to achieve this feat and have air that is completely free of allergy-triggering pollutants.
  • Does not remove microorganisms from the air, so it lacks germicidal capabilities.
  • Works better as an add-on rather than a standalone because of the filter media’s limitations.

Electret Filter Air Purifiers

Likely the most intriguing system of them all, the electret purifier works similarly to an ionic air purifier in the sense that it uses ions to attract the particles that linger in the air. Nonetheless, they do not fall under the filter-free category as a porous synthetic fiber material is used to create the charge in the system, trapping contaminants as they pass through just like any filter media does.


  • Quite effective in the removal of PM2.5 polluting particles from the air.
  • Absorbs particles using electrostatic force to improve filtering efficiency.
  • Airflow rate is quite high in these systems, which adds to their air cleaning speed.


  • Not a commonly used technology is residential air purification systems.
  • Air filtration efficiency has been discovered to decrease considerably (even up to 60%) over the years. Not a technology you can rely on in the long run.

Filter vs Filterless Air Cleaners - Side-by-Side Comparison

Filter System
Filter-Free System
Contaminants removed
Suited if you seek to combat odors, VOCs, allergens, dust, pet dander, smoke, and microorganisms.
Performant when it comes to the removal of bacteria and viruses.
Room size
Generally, the top area coverage provided by HEPA systems is 1,000 sq. ft.
With ionic air purifiers, are coverage can be as large as 3,500 sq. ft.
Energy consumption
Likely draw more power in their operation.
PCO systems consume a small amount of power to run.
Routine maintenance is required as filter media needs to be washed or replaced periodically.
Maintenance is generally required only once every few years.
The fans in their construction make them noisier.
Considerably more silent, producing a humming sound when they run.
Tolerance of by-products
By-products produced are trapped by the filters so that they are not released into the air.
By-products are released into the air during operation. Ionic systems produce ozone that can be harmful to people suffering from asthma.


In the end, it all boils down to what type of system best suits your needs – filter or filterless. Both come with their own set of advantages and drawbacks, there’s no denying it, and while filter air purifiers do a significantly better job at removing allergens from the air, ridding it of odors, and so on, filterless systems are much more effective when it comes to air sanitization, obliterating microorganisms and pathogens. All technologies and filter media are efficient up to a point and under specific circumstances, so it’s up to you to determine what you need and choose the air purification system accordingly.

Markus Mackay
Markus Mackay
Our resident expert in all things AC-related, Markus is a never-ending source of knowledge regarding how these systems work. What makes him so savvy in this field is his direct experience that he acquired while working in sales. The connections he made during that period also came in handy here as Markus knows a lot of experts in this field. With each article uploaded, he makes sure to gather the expertise of his more experienced ex-peers as well, making sure to provide readers with reliable reviews and articles.
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