How to choose the best air purifier

Choosing an air purifier for your home, flat, office, or other professional space may seem like a daunting task. There are many factors to keep in mind whilst making your choice, and with a market flooded with products and choices, it may be overwhelming. Don’t worry: we’re here to help! Read on to learn about what Eoleaf recommends as the best air filtration technologies.

Eoleaf's AEROPRO 40 air purifier surrounded by houseplants

What are the best air filtration technologies?

An air purifier is nothing without its filtration technologies. These vary significantly from device to device – some offer just one or two, and some offer multiple. The quality and variety of an air purifier’s filtration technologies will determine how well your indoor air will be filtered.

The following list includes all of the technologies offered by Eoleaf air purifiers (a whopping 8!) for the home or office. What makes each one important?


A pre-filter is a filter’s first line of defence. It traps larger air pollutants than one micron in size. This helps prolong a filter’s lifespan. When too many large airborne pollutants clog up a filter, it makes your unit work harder than it needs to, which has a longer-term impact on your device’s longevity, especially the motor.

A pre-filter captures:

Natural bamboo fibre

Bamboo contains a complex microstructure which gives it excellent particle filtration properties. It focuses mainly on medium-sized particles (particles that fall between the coarse particle category or the fine particle category).

Lysozyme and silver ion coating

Lysozyme and silver ions also both have antibacterial properties. Lysozyme serves an important role in the immune system, protecting the body against invaders like bacteria, viruses, and fungi1. Silver has antimicrobial properties and prevents bacterial infection2. Furthermore, its use does not lead to bacterial resistance.

Medical-grade H13 HEPA filter

A medical-grade HEPA-certified filter is widely considered the technology that obtains the highest-quality filtration available in the air purification market. By definition, high-efficiency particulate air (HEPA) is a designation given to filters that capture 99.97% of particles with a diameter greater than or equal to 0.3 microns in a single pass. Typically, these filters are made of water-resistant polypropylene fibres and have a 12-month lifespan, after which they require a filter change.

A bird's eye view of Eoleaf's AEROPRO 150 air purifier replacement filter

Why 0.3 microns? Particles with a diameter of 0.3 microns are considered to be the most difficult to filter, also known as ‘MPPS’ or ‘the most penetrating particle size’3. It is the worst case scenario. As a result, an air purifier equipped with a HEPA-certified filter is able to filter particles that are both larger and smaller than 0.3 microns even more efficiently. Our devices here at Eoleaf are able to capture ultrafine particles down to a size of 0.01 microns.

HEPA-certified filters are classified by filtration rate. The classes and their filtration rates are as follows:

  • H10
    • Filters 85% of pollutants from a room 
    • Allows 15,000 particles of 0.1 micron per litre of air to pass through
  • H11
    • Filters 99% of pollutants from a room 
    • Allows 10,000 particles of 0.1 micron per litre of air to pass through
  • H12
    • Filters 99.5% of pollutants from a room 
    • Allows 500 particles of 0.1 micron per litre of air to pass through
  • H13 (as used in Eoleaf products) 
    • Filters 99.95% of pollutants from a room 
    • Allows 50 particles of 0.1 micron per litre of air to pass through
  • H14
    • Filters 99.995% of pollutants from a room 
    • Allows 5 particles of 0.1 micron per litre of air to pass through

You may be wondering: if there is a HEPA filter with a higher filtration capacity (H14 filters), why not use those in our air purifiers? H14 filters do have a slightly higher filtration rate, but due to their incredibly small mesh, they slow down the flow of air into the air purification unit. H13 and H14 filters are both given the designation of ‘medical-grade’ or ‘hospital grade’ and are regularly found in hospitals and other medical institutions.

A HEPA filter captures:

  • Germs (bacteria and viruses)
  • Allergens (pollen, even fine pollen particles that have been fractured; dust; dust mites; mould and mould spores; pet dander)
  • Fine particles including PM10, PM2.5, and PM0.1

HEPA filters do have their limits which is why it is so important to purchase a device with complementary filtration technologies. HEPA filters do not filter chemical pollution like VOCs or ozone, but activated carbon filters and photocatalysis do! Read on below.

Activated carbon filter

Activated carbon filters (activated carbon is also referred to as activated charcoal) have been used for filtration for centuries. The first recorded usage of activated carbon filters is traced back to 1500 BC when the ancient Egyptians used it for combatting odours caused by infection in medical settings. Since then, it has been used by 16th century sailors to store drinking water in barrels, in gas masks to protect soldiers from inhalation of deadly gases during World War I, and, finally, for water and air filtration applications during World War II4. You can now find activated carbon filters in both home and professional settings: in water and air filters, aquariums, cigarette filters, and more.

Activated carbon filters use a process called ‘adsorption’ where carbon molecules attract pollution particles (organic, chemical, and gaseous). These pollution particles then stick to the outside of the carbon molecules. When carbon is activated, it increases its surface area, and this creates more space where pollution particles can stick.

An activated carbon filter captures:

How the adsorption process works in activated carbon


Photocatalysis, or photocatalytic oxidation, is a popular depollution technology that removes contaminants from both air and water. It does not filter pollutants; rather, it degrades and destroys them. It works as a simple reduction-oxidation (redox) reaction: a semiconductor, usually titanium oxide (TiO2), is activated by a catalyst, light (ultraviolet light rays). Once the semiconductor is activated, airborne pollutants, especially chemical pollution, are degraded and decomposed.

In an Eoleaf air purifier, when the UV lamps used for UVC sterilisation technology emit UV rays, those rays strike and activate the multi-layer filter which contains TiO2. The reaction generates free radicals which have depolluting capabilities. The free radicals are then very effective at destroying air pollutants.

Photocatalysis removes:

  • Chemical pollutants like volatile organic compounds (VOCs)
  • Other toxic gases and gaseous pollutants

Ultraviolet (UVC) sterilisation

Ultraviolet sterilisation is an extremely effective sterilisation method against germs of all kinds (both bacteria and viruses like COVID-19). UV light is broken down into three types, distinguished by wavelength:

  • UVA rays have the longest wavelength (315 to 400 nm) with the most potential to penetrate and cause damage to the middle layer of the skin (the dermis); exposure to this type is most likely to lead to skin cancer
  • UVB rays have a wavelength shorter than UVA rays (280 to 315 nm); they are usually unable to penetrate deeper than the outer layer of the skin (the epidermis)
  • UVC rays have the shortest wavelength (100 to 280 nm) and the highest energy potential of all UV rays, giving them the best capacity to destroy and inactivate pathogens (bacteria and viruses); since they are a low-penetrating form of UV light, they are most commonly used in air purifiers due to the limited danger they pose to humans

UVC sterilisation technologies use UVC light with a 254 nm wavelength. This wavelength has proven to be the safest, most effective wavelength in reducing pathogen transmission. It is a widely-used technology in hospital settings, pharmacies, and elsewhere in the medical sector. It does not lead to bacterial resistance, and it works on all germs regardless of size or shape. UVC rays emitted at 254 nm produces zero or very minimal ozone5.

UVC sterilisation removes:

  • Bacteria
  • Viruses including MRSA, SARS, and COVID-19
  • Microbes

Ionisation (negative ions)

Eoleaf’s devices serve as both air purifiers and ionisers. Like photocatalysis, ionisation does not filter air pollutants; an ioniser diffuses negative ions into the ambient air. Negative ions are negatively-charged, making them highly reactive and an effective depollution method. Pollution particles are positively-charged. When negative ions attach themselves to pollution particles, it will either cause the pollutants to disintegrate or weigh them down, causing them to fall down to the ground. This protects you from inhaling them. Many people with allergies benefit from the presence of an ioniser in their indoor space since negative ions bind to pollen particles and other allergens.

Ionisation removes:

  • Particulate matter (PM) generated by fine particle pollution, smoke, dust, and pollen
  • Preliminary studies are showing promising results in negative ions’ abilities to fight harmful bacteria and viruses, especially the flu virus6

Eoleaf's AEROPRO 100's replacement filter with leaves

What to consider when choosing the best air purifier?

Room size/floor area

All air purifiers are designed to filter the air of a maximum room size/floor area. Be sure to choose a device that is properly sized to your space! Eoleaf’s devices are designed for the following room sizes:

  • AEROPRO 40: filters the air in rooms up to 40 m2 (430 square feet)
  • AEROPRO 100: filters the air in rooms up to 80 m2 (860 square feet)
  • AEROPRO 150: filters the air in rooms up to 120 m2 (860 square feet)
  • Pure CAR: filters the air in rooms up to 13 m2 (1290 square feet)

Cost, lifespan, and stock of replacement filters

When choosing an air purifier, it is important to consider the three parts involved in an air purifier’s budget:

  • The initial cost of the device – this can vary significantly (£200 to £1000) depending upon the technologies and options offered
  • Maintenance costs – all air purifiers require filter changes as part of their regular maintenance, but higher-quality devices will require them less often (Eoleaf devices only requires annual filter changes)
  • Costs associated with energy usage – this varies depending upon your usage of the device, but it is important to invest in an energy-efficient air purifier (see below)

When choosing the right air purifier model for you, be sure to choose one that guarantees your device’s longevity. Companies that offer long warranties are confident in their products! Eoleaf air purifiers are built to last and are covered under warranty for three years. The same goes for Eoleaf’s air purifier replacement filters: as mentioned above, their high-quality design means that they only need to be changed once a year. Our devices are equipped with a convenient filter change indicator to let you know when it is time for a filter change, making maintenance easy.

Another thing to keep in mind is stock of air purifier replacement filters. Eoleaf’s filters are all in stock. Our replacement filter pricing is as follows:

  • Replacement filter for our AEROPRO 40 model: £114.99
  • Replacement filter for our AEROPRO 100 model: £129.99
  • Replacement filter for our AEROPRO 150 model: £169.99
    • Replacement pre-filter for our AEROPRO 150 model: £29.00
  • Replacement filter for our Pure CAR model: £33.99

Air Changes per Hour (ACH) and Clean Air Delivery Rate (CADR)

Air Changes per Hour, or ACH, is how many times per hour an air purifier renews a room’s entire volume of air with purified air. The Centre for Disease Control (CDC) recommends a minimum ACH value of 5, meaning that a device replaces the air 5 times per hour.

Clean Air Delivery Rate, or CADR, is a bit different. It refers to the airflow of the air purification device. This refers to the volume of filtered air that an air purifier can deliver in your space. Air purifiers may differ with some having just one CADR number and others having multiple CADR numbers for specific pollutants (dust, smoke, pollen, etc.). The higher the CADR number, the faster a device filters out pollutants.

Find Eoleaf’s CADR numbers below:

  • AEROPRO 40: 420 m3/hr
  • AEROPRO 100: 570 m3/hr
  • AEROPRO 150: 670 m3/hr
  • Pure CAR: 45 m3/hr

Energy consumption

Invest in an air purifier that consumes minimal energy. Both your energy bills and carbon footprint will thank you! An energy-efficient device should not cost more than £5 to £10 per month in energy costs, even when left running 24/7.

An energy-efficient air purifier comes equipped with display dimming, programmable timers, and smart scheduling. These are all great ways to reduce energy usage. Eoleaf’s devices all offer these features, and you can even control your Eoleaf air purifier all from your smartphone. Using the Tuya Smart smartphone app, you can choose when your device increases its fan speed, when it turns on the ionisation feature, when it switches into Automatic mode, and more. Find this smart feature and more with Eoleaf devices including:

  • Handheld remote control
  • Gesture control
  • Voice commands via Alexa, Siri, or Google Assistant

A hand using gesture controls over Eoleaf's AEROPRO 100 air purifier

Noise level

You should be able to harness all of the benefits that come with an air purifier without having to deal with distracting noise. It should not disturb you whilst you sleep, work, or study. In professional spaces, it should never disturb your customers or patients. A quiet air purifier is one that is near-silent on its lowest fan speed and never exceeds 70 dB (noises above this level contribute to hearing loss when sustained), even at its highest fan speed level. 70 dB equates to typical office noise.

Even when set on its fastest fan speed (speed 5), Eoleaf air purifiers never exceed 70 dB. Our devices also have a night-time setting or ‘Night mode’. This sets our air purifiers at their lowest fan speed and dims the indicator lights, allowing you to enjoy a disturbance-free sleep.

Your needs

Before you consider any of the above features of your prospective air purifier, the first question should be: what are your needs?

If you answered ‘yes’ to any of the previous questions, purchasing an air purifier may be exactly what you need to achieve a better quality of life.

The Eoleaf difference

There are many reasons why you might consider purchasing an air purifier but one thing remains consistent: you want to protect your health and the health of those around you. Remember: indoor air is 2 to 5 times more polluted than outdoor air!

Protecting your health from indoor air pollution and poor indoor air quality is what we strive to do here at Eoleaf. Our air purification experts are here any time to help you in your goal to breathe clean air indoors. We also encourage you to refer to our Buying Guide for even more information of what to consider before purchasing an air purifier.

Eoleaf's AEROPRO 150 air purifier in a bright room

Frequently asked questions (FAQs)

What's the best air purifier to buy?

Seek out an air purifier that comes with more than one purification technology to combat all types of air pollution and improve indoor air quality. Always ensure that HEPA filters are certified and not ‘HEPA-type’.

Where is the best place to put an air purifier?

Avoid placing your air purifier where its inlets or outlets will be obstructed. Do not place it in a corner or behind furniture. Ideally, it should be in the centre of a room where there is optimal air flow.

What is the best air purifier for mould in 2023?

Try Eoleaf’s AEROPRO 100 air purifier. It is designed to filter the air in spaces of most sizes. With its powerful, medical-grade H13 HEPA filter (along with its 7 other purification technologies), this HEPA air purifier will remove airborne mould spores before they have the chance to spread to other places in your home or at work.

Which type of air purifier is best for your home?

An air purifier that purifies all types of indoor air pollution in order to improve indoor air quality (IAQ) is best. This includes biological pollution (allergens like dust and dust mites, pollen, germs, pet hair and dander, and mould), chemical pollution (VOCs including carcinogenic VOCs like formaldehyde and benzene; ozone; and other toxic gases), and fine particle pollution (PM10, PM2.5, and PM0.1).

What to avoid when buying an air purifier?

Avoid 2-in-1 or 3-in-1 devices or units that claim to cool or heat the air and purify simultaneously. Even if it is a HEPA air purifier, air purifier filter fibres are sensitive to drastic changes in temperature, and cooling/heating functions will reduce their ability to filter the air.



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2 Sim W, Barnard RT, Blaskovich MAT, Ziora ZM. Antimicrobial Silver in Medicinal and Consumer Applications: A Patent Review of the Past Decade (20072017). Antibiotics (Basel). 2018 Oct 26;7(4):93. doi: 10.3390/antibiotics7040093. PMID: 30373130; PMCID: PMC6315945.

3 Environmental Protection Agency. (2023, March 13). What is a HEPA filter? . EPA.

4 Historic journey of activated carbon and breakthroughs . Camfil. (2020, April 7). Retrieved March 3, 2023, from

5 Beck, S. E., Rodriguez, R. A., Hawkins, M. A., Hargy, T. M., Larason, T. C., & Linden, K. G. (2015). Comparison of UV-induced inactivation and RNA damage in MS2 phage across the germicidal UV spectrum. Applied and Environmental Microbiology, 82(5), 1468–1474. doi:10.1128/aem.02773-15

6 Hagbom M, Nordgren J, Nybom R, Hedlund KO, Wigzell H, Svensson L. (2015, June). Ionizing air affects influenza virus infectivity and prevents airborne-transmission. Retrieved from

Eoleaf's range of air purifiers

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