How does an air purifier work? An air purifier draws contaminated indoor air into the unit, where filters or treatment technologies capture, remove or break down pollutants such as PM2.5, pet dander, pollen, mould spores and odours. The treated air is then released back into the room, creating a […]
An air purifier draws contaminated indoor air into the unit, where filters or treatment technologies capture, remove or break down pollutants such as PM2.5, pet dander, pollen, mould spores and odours. The treated air is then released back into the room, creating a continuous air circulation cycle that helps improve indoor air quality.
Traditional purifiers rely mainly on filtration, while advanced systems may combine HEPA filtration with active technologies such as Vapour Phase Oxidation (VPO) to address airborne contaminants and certain pollutants on surrounding surfaces.
If you’ve ever sat in your living room on a sunny afternoon and noticed tiny particles of dust floating through the beam of light coming through the window, you’re not imagining it.
In fact,the air inside your home contains far more than visible household dust. It can also contain pet dander, dust mite allergens, mould spores, pollen, volatile organic compounds (VOCs), formaldehyde and other airborne irritants. However, Even with regular vacuuming, mopping and cleaning, some of the smallest particles can remain suspended in indoor air and circulate through the breathing zone.
This is one reason many people are turning to air purifiers as part of their indoor air quality strategy.
But how does an air purifier actually work?
Does that box simply pull air in and push it back out through a filter? Can it really help reduce the pollutants found inside a home? And how do you know whether a particular air purifier is suitable for your room?
This guide explains the science behind air purification, the technologies used in modern air purifiers, and the key factors to consider when choosing an air purifier for an Australian home.
An air purifier improves indoor air quality by continuously circulating and treating the air within a room.
Specifically, the unit uses a fan to create a pressure difference that draws contaminated indoor air into the system. The air then passes through one or more filtration or treatment stages designed to capture particles, remove pollutants or break down certain contaminants. Finally, treated air is released back into the room, where it mixes with the surrounding air and helps reduce pollutant concentrations over repeated circulation cycles.
This process can be understood as a continuous air circulation and dilution cycle.
Indoor pollutants are not limited to the dust we can see. Homes can also contain a mixture of allergens, irritants, gases and microorganisms that may remain airborne or accumulate on surfaces.
In fact, these pollutants can be difficult to identify because many are invisible. Depending on the pollutant and the technology being used, an air purifier may help capture airborne particles, reduce certain pollutants or provide additional treatment of the indoor environment.
Most air purification systems can be understood through three basic stages: Air Intake, Treatment & Filtration, and Clean Air Delivery.
The internal motor and fan create airflow that draws surrounding room air into the air purifier.
The incoming air may first pass through a pre-filter, which captures larger particles such as hair, visible dust and other debris. As a result, this helps prevent larger contaminants from reaching and prematurely loading the finer filtration stages.
Once larger particles have been removed, the air moves through the main treatment system.
In a conventional air purifier, this stage typically relies on a dense filter media designed to capture fine airborne particles. A HEPA filter, for example, is designed to capture very small particulate matter as air passes through the filter.
Furthermore, more advanced air purification systems may combine particle filtration with additional treatment technologies. Depending on the system, this can include technologies designed to address gases, odours or other contaminants that conventional particle filtration alone may not fully address.
One example is Vapour Phase Oxidation (VPO), an active air treatment technology designed to distribute a treatment agent through the environment rather than relying solely on contaminated air reaching a passive filter.
After treatment, the air is pushed back into the room through the air outlet.
The resulting airflow mixes with the surrounding room air, creating continuous circulation. As the process repeats, more of the room’s air passes through the purification system.
This is why factors such as CADR, airflow rate, room volume and Air Changes per Hour (ACH) are important when assessing how effectively an air purifier can treat a particular space.
Traditional air purifiers primarily work by bringing contaminants to the filter.
Although this is highly useful for airborne particles, but filtration has a fundamental limitation: the pollutant generally needs to enter the airflow and physically reach the filter before it can be captured.
This is where active treatment technologies take a different approach.
Rather than relying exclusively on airflow to bring contaminants to a filter, an active treatment system can introduce a treatment process into the surrounding environment.
Vapour Phase Oxidation (VPO) is one example. It uses a controlled vapour-phase treatment to interact with selected contaminants in the air and environment. When combined with particle filtration, this creates a dual approach: filtration for airborne particles and active treatment for pollutants that may not be effectively addressed by filtration alone.
The exact capabilities depend on the technology, concentration, operating conditions and specific air purifier design.
Air purification depends not only on the filter inside the machine, but also on how effectively air moves throughout the room.
A conventional air purifier relies on its fan to draw surrounding air towards the intake. As the distance from the unit increases, airflow can become less direct, particularly in rooms with furniture, walls, corners and other obstacles.
Consequently, areas with limited air movement are sometimes described as dead air zones.
For example, air around corners, underneath furniture or behind large objects may circulate more slowly than air immediately surrounding the purifier. Pollutants deposited on carpets, upholstery, curtains or bedding may also remain on those surfaces rather than being immediately drawn into the air purifier.
This is an important distinction when evaluating air purification technology:
A filter can only capture airborne contaminants that actually reach the filter.
Good room placement, appropriate airflow and sufficient circulation remain important factors in achieving effective air purification.
For this reason, simply choosing a purifier with a high headline filtration efficiency does not necessarily tell the whole story. Room size, CADR, airflow distribution, operating speed, ACH and the type of pollutants you want to address all matter when selecting an air purifier.
The key difference between these technologies is how they interact with indoor pollutants.
Conventional filtration systems such as Mechanical HEPA and Activated Carbon primarily rely on contaminated air being drawn into the air purifier, where particles or gases are captured by the filter media.
By contrast, Vapour Phase Oxidation (VPO) is an Active Environmental System that uses a controlled vapour-phase treatment to interact with selected contaminants in the air and surrounding environment.
Understanding this difference is important when choosing an air purifier because no single technology is designed to address every type of indoor pollutant in exactly the same way.
Let’s look at how the major air purification technologies work and where each one fits within a modern indoor air quality system.
However, HEPA filtration also captures microorganisms within the filter media, but capture does not necessarily mean immediate inactivation or destruction. If odours, VOCs or certain microorganisms are a key concern, additional technologies such as Activated Carbon or Active Air Treatment may be used alongside HEPA filtration.
Carbon also has a finite adsorption capacity. As adsorption sites become occupied, its ability to capture additional compounds can decrease. Regular filter replacement is therefore important and should be based on the manufacturer’s recommendations and the conditions in which the purifier operates.
Some ionisation and plasma technologies may also produce ozone (O₃) as a by-product, depending on their design and operating conditions.
For people looking for an air purifier for enclosed indoor spaces, ozone-free operation or independently verified low-ozone performance can therefore be an important consideration when comparing technologies.
How it works: Vapour Phase Oxidation (VPO) is an Active Air Treatment approach that does not rely solely on drawing contaminated air through a passive filter. Instead, a controlled vapour-phase treatment is dispersed through the indoor environment, allowing it to interact with selected contaminants in the air and on accessible surfaces.
An Active Treatment system can work alongside HEPA filtration to address different categories of indoor pollutants.
HEPA filtration focuses on airborne particles such as:
An active treatment process may provide an additional mechanism for addressing odours and certain chemical compounds, including selected VOCs, depending on the technology and operating conditions.
This creates a more comprehensive approach than relying on particle filtration alone.
A conventional filter can only capture contaminants that are carried into the unit by airflow.
In contrast, a vapour-phase treatment is distributed from the system into the surrounding environment. This means the treatment process is not limited exclusively to air that passes directly through the filter.
Depending on the technology, operating conditions and exposure time, this may allow treatment to interact with selected contaminants present in areas such as carpets, upholstered furniture, bedding and other accessible indoor surfaces.
Activated Carbon primarily works through adsorption, holding certain gas molecules on the surface of the carbon.
Oxidation-based treatment works differently. Selected compounds can undergo a chemical reaction that changes their molecular structure.
The effectiveness of this process depends on factors including the type and concentration of the contaminant, treatment concentration, contact time, airflow and system design.
As a result, VPO should be viewed as a complementary treatment mechanism rather than a universal replacement for mechanical filtration.
For residential applications, controlling treatment levels and managing potential by-products are important considerations.
The EnviroGuard PRO™ X combines Active Vapour Technology with HEPA-13 filtration to provide two complementary treatment mechanisms within one system.
Its active vapour system is designed without using ozone as the primary oxidising agent, while the HEPA-13 filtration stage provides mechanical filtration of airborne particles.
| Feature / Capability | Mechanical True HEPA | Activated Carbon | Ioniser / Plasma |
Complete System Vapour Phase Oxidation (Environmental System) |
|---|---|---|---|---|
| Primary mechanism | Passive mechanical filtration | Passive adsorption | Active particle charging | Active environmental treatment |
| Dust / pet hair / pet dander / pollen |
Effective particle capture
|
Not applicable
|
Depends on system design
|
Used alongside HEPA filtration
|
| Dust mite allergens / mould spores |
Captures airborne particles
|
Not applicable
|
Depends on system design
|
Used alongside filtration and active treatment
|
| Odours and VOCs |
Limited
|
Adsorbs certain compounds
|
Not the primary function
|
Can react with selected compounds
|
| Airborne bacteria & microorganisms |
Can capture particles (but capture does not mean inactivation)
|
Not the primary function
|
Depends on technology and design
|
Active treatment may interact with selected contaminants
|
| Treatment of accessible surfaces |
Primarily limited to air passing through the unit
|
Primarily limited to air passing through the carbon media
|
Depends on system design
|
Vapour-phase treatment can extend into the surrounding environment
|
| Contaminants away from the unit | Dependent on room airflow and circulation | Dependent on room airflow and circulation | Dependent on ion distribution | Designed for distribution throughout the treated environment |
| Multi-pollutant approach | Primarily particles | Primarily gases and odours | Primarily particles | Combines active treatment with mechanical filtration |
| Pollutant accumulation in media | Yes — particles accumulate on the filter | Yes — selected compounds are adsorbed by carbon | Depends on system | Active treatment can chemically transform selected compounds |
| Ozone considerations | Not the primary mechanism | Not the primary mechanism | Depends on system design | EnviroGuard PRO™ X does not use ozone as its primary oxidising agent |
| Role in EnviroGuard PRO™ X | HEPA-13 filtration | Carbon filtration | Active Vapour Technology + Environmental Treatment |
There is no single filtration technology that performs every function equally well.
Therefore, when comparing air purifiers, consider the type of pollutants you want to address:
Australia’s environment presents a unique set of Indoor Air Quality (IAQ) challenges. Specifically, these conditions can mean that a conventional filter-based air purifier may not address every type of airborne pollutant that can affect the indoor environment of Australian homes and the people and pets living in them.
For a healthier indoor environment, choosing an air purifier in Australia means considering three important environmental factors:
Bushfire smoke contains more than fine PM2.5 particles, which can be captured by HEPA filtration. In addition, it can also contain gaseous pollutants and volatile organic compounds (VOCs), including compounds such as benzene and formaldehyde, generated during the combustion of vegetation and other materials. Addressing these pollutants may require additional gas-phase treatment alongside particle filtration.
(Read more: How to Manage Indoor Air Quality During a Bushfire)
In coastal states such as New South Wales and Queensland, periods of high humidity and wet weather can create conditions that support mould growth in poorly ventilated areas, including around walls and other damp surfaces. A conventional air purifier can capture airborne mould spores that pass through the unit, while technologies such as Vapour Phase Oxidation are designed to disperse an active vapour throughout the environment and provide treatment beyond the immediate filter airflow path.
(Explore the issue in more detail: Air Purifiers for Mould Spores in the Home)
Seasonal pollen is a significant consideration for people affected by hay fever and pollen allergies across Australia. In particular, Ryegrass Pollen is an important seasonal allergen in parts of Victoria and other southern regions. When choosing an air purifier for allergy management, factors such as a sufficiently high Air Changes per Hour (ACH) and recognised programmes or certifications such as Sensitive Choice may be relevant considerations for people looking to reduce airborne allergen exposure.
(Learn more: How to Manage Indoor Air Quality for Allergies and Hay Fever)
Choosing the right air purifier size should not be based solely on the “Maximum Room Size” stated on the product packaging. Instead, you should calculate the required Clean Air Delivery Rate (CADR) based on the actual volume of the room. For a typical home, an air exchange rate of at least 2 to 3 Air Changes per Hour (ACH) is generally recommended. Homes with pets or people with allergies may require a higher air circulation rate of around 4 to 5 ACH to help keep up with the continuous release of pet dander, fur and other airborne allergens.
| Room Area | Volume | Suitable Room Type | Typical Home (2.5 ACH) |
Pets / Allergies High Allergen Load (4.8 ACH) |
|---|---|---|---|---|
| 15 m² | 39 m³ | Small bedroom, home office | 98 m³/h (58 CFM) | 187 m³/h (110 CFM) |
| 25 m² | 65 m³ | Large bedroom, studio apartment | 163 m³/h (96 CFM) | 312 m³/h (184 CFM) |
| 35 m² | 91 m³ | Medium-sized living room, one-bedroom apartment | 228 m³/h (134 CFM) | 437 m³/h (257 CFM) |
| 50 m² | 130 m³ | Open-plan living area, combined living and kitchen space | 325 m³/h (191 CFM) | 624 m³/h (367 CFM) |
If your home has a large open-plan layout, such as a living area connected to a cat litter area or a dog's sleeping space, relying on a single large air purifier may not always provide even air circulation across every zone. An air purifier used alongside Vapour Phase Oxidation can provide an additional approach to environmental treatment, as the active vapour is designed to disperse through the environment rather than relying solely on the fan's airflow to draw contaminants towards a filter.
Choose an air purifier based on the pollutants you need to manage — not a single specification.
Check CADR/ACH, pollutant-specific technology, ozone emissions, real-world noise and 3–5 year ownership costs before comparing products.
HEPA captures particles; Activated Carbon adsorbs certain gases and odours; active treatment technologies such as Vapour Phase Oxidation provide an additional mechanism for addressing certain contaminants.
Upgrade to the innovative EnviroGuard PRO™ X today for only $790 (Was $1,590). Claim your $800 saving now and breathe cleaner, healthier air tomorrow.
¹ Tested in independent Australian laboratories under controlled conditions using airborne mould spores, bacteria and allergen particulates (0.3μm–10μm).
² Based on third-party testing results confirming 99.9% reduction in airborne mould spores and pet dander when using EnviroGuard Pro X with Purox™ Gel over 24 hours.
³ Independent testing by ICAS Testing Technology Service (Shanghai) Co., Ltd. demonstrated 99.99% reduction in airborne Staphylococcus Albus bacteria within 30 minutes in a 20m² test chamber, in accordance with Technical Standard for Disinfection GB 27948-2020.
⁴ Surface efficacy testing conducted by Eurofins BioPharma Product Testing — Sydney (Eurofins ams Laboratories Pty Ltd, TGA-licensed under MI-2021-LI-08995-1). Reductions over 8 hours: 99.99% Pseudomonas Aeruginosa, 99.9% Escherichia Coli, 90% Candida Albicans Yeast.
⁵ "10x faster than conventional filtration" comparison based on EnviroGuard Pro X achieving log 4 (99.99%) airborne bacterial reduction in 30 minutes, compared with log 1 (90%) pathogen reduction in 20 minutes reported for hospital HEPA systems operating at 12 air changes per hour (Fernstrom A, Goldblatt M. Aerobiology and its role in the transmission of infectious diseases. J Pathog. 2013;2013:493960).
⁶ Performance varies based on room size, airflow configuration, fan speed setting, environmental conditions and usage patterns.
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