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Air Filtration vs Air Purification April 27, 2020


What is the difference between air filtration and air purification? They are the same thing, right?

Nope! It is perfectly understandable to confuse the two, but filtration and purification are two different processes with different efficacy for different pollutants.


Air Filtration

Air filtration is a mechanical process by which air filters remove particulate matter (dust, mites, pollens, toxin etc.) from the air by trapping, arresting or intercepting particles as the air passes through the filter.


Air Filter Classifications:


HEPA filter

HEPA (High Efficiency Particulate Air Filters)

High Efficiency Particulate Air filters are the most sophisticated air filter technology available. They were first designed in WW2 to stop radiation exiting laboratories, and this same technology is still the most advanced air filtration available. What sets these filters apart is their effectiveness. They are all rated 17 or more in terms of filtration efficiency and to be certified as a true HEPA filter, they must trap 99.97% of particulates 0.3 microns or larger.


ISO 16890 (Particulate Matter | PM)

This is the international standard for air filters and divides air filters into four groups. It puts the focus on the classes of particulate matter size (PM) as the distinguishing test criteria. The prerequisite for a filter to be rated at in one of the groups, is that it must demonstrate efficiency of 50% or greater at this PM size. The four size groups:

  • ISO ePM1: ePM1 min ≥ 50% [viruses, nanoparticles, exhaust gasses]
  • ISO ePM2,5: ePM2,5 min ≥ 50% [bacteria, fungal and mould spores, pollen, toner dust]
  • ISO ePM10: ePM10 ≥ 50% [pollen, desert dust]
  • ISO Coarse: ePM10 ≤ 50% [sand, hair]

ISO16890 means filter efficiencies are determined based on particulate matter size classes PM1, PM2.5 and PM10 (also called ePM1, ePM2,5 and ePM10), which are also used as evaluation parameters by the WHO (World Health Organization) and other authorities. Based on these parameters it makes it simple for users to select the right air filter based on their requirements. Source: (AFPRO, 2020)

“It makes the comparison between your outside air quality and the indoor air quality you require. Then it tests the ability of a filter to arrest PM across a range of sizes to help you choose the correct filter grade.” Read an Indoor Air Quality experts unpacking of the ISO16890 standard here.


Air Purification

This is the process of sanitising air by neutralising airborne toxins (gases, bacteria, viruses, fungi, toxic pathogens). Rather than trap particles with a mechanical process like air filters, air purifiers emit something (UV, Ions, Electrostatic etc. depending on the type of purifier) to ‘kill, neutralise, transform or otherwise render airborne toxins harmless.’ (CleanAir Solutions, 2020)


Types of Air Purifiers:


Ultraviolet purification replicates the Suns natural purifying rays. The UV rays incur cellular or genetic damage to the pollutants – inactivating or destroying them. They can kill/neutralise airborne toxins, pathogens, viral and fungal matter, mildew, mould spores, pollen, dust mites and odour.


Photocatalytic oxidation

There is evidence to support that this is the most effective air purification technology, due to its ability to destroy particles as small as 0.001 microns (to put this into perspective, HEPA filters can only filter particles as small as 0.3 microns). This process destroys all microbes, VOC’s, CACs, viruses and its efficacy has been proven against most other air pollutants.


Photocatalytic Oxidation purification process


Activated carbon

Activated carbon is highly effective in trapping gases and chemicals in the air, such as VOC’s, smoke and odour. Activated carbon is super porous material (1 gram of activated carbon can have an internal surface area of 100m2 [Ohio EPA]), and traps gases through adsorption. Activated carbon cannot remove fine particles like mould, dust or pollen from the air so typically is only one element of an air purifier and is combined with pre-filtration and final stage HEPA filtration.



These purifiers use electrostatic attraction (electrically charged particles) to remove fine particles (dust, smoke) from the air. This charge causes the particles to be attracted and trapped by a series of flat collector plates that have the opposite charge. The process is similar to Ionisers but is in a controlled chamber. These purifiers to require frequent cleaning of the collector plates, as the efficiency of these reduce dramatically as they fill up.

Ionizers & Ozone generators

Whilst both processes utilise slightly different molecules both work in a similar way. When the charged Ions or Ozone molecules come into contact with normal particulate matter in the air, it gives it a charge and causes it to stick to a surface to neutralise the charge. However, these methods have been proven largely ineffective, as they do not eliminate the particles, and the particulate matter can very easily return to the air, contaminating it once again.

Ozone generators have also been widely condemned by health professionals due to the potential health related side effects.


Filtrations vs Purification

Filtration is the process of trapping particulate matter, whereas purification is the elimination of toxins from the air.

However, to get the purest, cleanest air, both processes should be utilised together. The air filters trap airborne particles, whilst the air purifiers kill all the airborne toxins, pathogens and viruses – leaving only clean, pure, fresh, oxygenated air. Filtration prior to purification also enhances the efficacy of the purifier, as it removes the larger particles from the air, allowing the purification chamber to be most effective.


Please note: both processes require careful research before being implemented into a HVAC system. If the wrong filters, or cheap knock offs, are used it can be about as effective as using Grandma’s knitting for filtration. Similarly, if cheap air purifiers are used (there are so many available on the market!) it is about as worthwhile as using your vacuum cleaner to neutralise pathogens and toxins in the air!

SO, if you are looking to invest in CLEAN AIR, make sure you purchase certified, quality equipment.

If you ever wish for consultation on your HVAC or assistance with your Indoor Air Quality, feel free to reach out. Our IAQ experts are always willing to help.


Denver Prestidge, business development manager

About the Author:

Denver Prestidge is a fresh Industrial Hygiene and Air Quality apprentice for Presco Environmental.

Focused on sourcing and developing innovative, industry leading products for New Zealand’s food producers, Denver is always looking for ways to challenge and improve the status quo.

If you would like to get in touch with Denver, feel free to reach out at any time – denver@presco.co.nz


Hepa filter image retrieved from afprofilters.com.

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