Improving Indoor Air Quality in New Zealand

If you’re dealing with mould in your home, it’s natural to look for solutions that improve the air you breathe. Many people search for an air purifier for mould hoping it will fix the problem entirely. The reality is more nuanced. Air purifiers can help reduce airborne mould spores, which may improve comfort and air quality. However, they don’t stop mould from growing. That’s because mould is caused by moisture, not dirty air alone. This article explains: How air purifiers help with mould Why HEPA filtration and high CADR matter What air purifiers can’t do How to set realistic expectations for mould control Quick Summary: Air Purifiers for Mould Mould growth is caused by excess moisture, not poor air circulation alone Air purifiers do not reduce humidity or remove mould from surfaces A properly sized air purifier can help by capturing airborne mould spores HEPA filtration + high CADR are the two most important features Long-term mould control still requires dehumidification and ventilation Table of contents 1. What mould is - and why it affects indoor air quality 2. What actually causes mould growth (important context) 3. How air purifiers help with mould 4. Why HEPA filtration and high CADR matter for mould 5. What air purifiers can't do (setting expectations) 6. The role of dehumidification and ventilation 7. Air purifier & dehumidifier combo units 8. Where an air purifier fits in a mould management plan 1. What mould is - and why it affects indoor air quality Mould is a type of fungus that thrives in damp, poorly ventilated environments. It spreads by releasing microscopic spores into the air, which can remain airborne for long periods. Common places mould appears in NZ homes include: Bathrooms and laundries Bedrooms with poor ventilation Wardrobes Behind furniture or curtains When inhaled, mould spores can irritate the airways and may worsen symptoms for people with asthma, allergies, or respiratory sensitivities. 2. What actually causes mould growth (important context) Mould is a moisture problem first. Mould growth is driven by: High indoor humidity Condensation on cold surfaces Poor ventilation Leaks or water damage Until moisture is controlled, mould will continue to return - regardless of how clean the air is. 3. How air purifiers help with mould Air purifiers don’t stop mould from growing, but they can still help in certain ways. What air purifiers can do: Capture airborne mould spores Reduce the spread of spores to other rooms Improve overall indoor air quality Help reduce exposure after mould has been cleaned Reduce symptoms in those with mould sensitivities This can be especially helpful: After visible mould has been removed During damp seasons when spores are more common In bedrooms or living areas where people spend long periods How this works (simple explanation) Air purifiers pull air through a filter. If that filter is a HEPA filter, it will physically trap mould spores as the air passes through. This doesn’t remove mould already growing on walls or ceilings. But it can help reduce what’s floating in the air, which is often what causes symptoms. 4. Why HEPA filtration and high CADR matter for mould Not all air purifiers are equally effective at dealing with mould spores.  Two things matter most: 1. HEPA Filtration HEPA filters are designed to physically capture fine particles, including mould spores. This is essential, without HEPA filtration, spores may simply pass straight through the purifier. 2. High CADR (Clean Air Delivery Rate) CADR tells you how much clean air a purifier can deliver per hour. This matters for mould because: Spores are constantly being released into the air Activity in the home keeps particles airborne The purifier needs to clean the air repeatedly, not just once A purifier with HEPA filtration but low CADR may technically capture spores, but not fast enough to make a meaningful difference. Important to know: For mould, HEPA filtration + sufficient CADR work together. A strong filter without enough airflow (CADR), or airflow without proper filtration, won’t deliver reliable results. Smart Air SA600: Quickly & Quietly capture airborne mould spores Key features: Runs as quiet as 16 dB on low, suitable for bedroom usage Scales up to cover living areas up to around 65 m² Reaches 51 dB at full power when maximum airflow is needed Uses true HEPA filtration for dust, pollen and PM2.5 No ionisers or ozone-producing technologies Shop Smart Air SA600 5. What air purifiers can't do (setting expectations) Air purifiers do not: Reduce indoor humidity Dry out damp rooms Stop condensation Kill mould growing on walls or ceilings If moisture remains, mould will continue to grow. Even if the air is filtered. 6. The role of dehumidification and ventilation To properly manage mould, the priority should be: Reducing indoor humidity Improving ventilation Supporting air quality with an air purifier Common approaches include: Using a dehumidifier in damp rooms Ventilating bathrooms and kitchens Opening windows when conditions allow Addressing insulation or heating issues Once moisture is under control, air purifiers can help keep airborne mould spores lower. But they’re not a replacement for moisture management. 7. Air purifier & dehumidifier combo units You’ll also see products marketed as air purifier + dehumidifier combo units. While these can save space, they usually involve compromises. In practice: The dehumidifier side is often underpowered for anything beyond a small room The air purifier side typically has low airflow, making it far less effective than a standalone unit Performance falls short for larger bedrooms or living areas Because of this, combo units are generally only suitable for very small spaces, and even then with limited expectations. For most homes, we recommend using separate, purpose-built units. A dehumidifier to control moisture, and an air purifier to help reduce airborne particles like mould spores. If you’re curious about how these combo units compare in more detail, we’ve covered them in a separate article.👉 Read our guide to air purifier and dehumidifier combo units 8. Where an air purifier fits in a mould management plan Air purifiers work best: After visible mould has been cleaned Alongside dehumidification or ventilation In rooms where people spend the most time They’re best viewed as a supporting tool, not a standalone fix. Wrap-up: the honest takeaway on air purifiers for mould: Mould problems are ultimately moisture problems. An air purifier won’t stop mould from growing, but a properly sized HEPA air purifier with high CADR can help reduce airborne mould spores and improve overall air quality. For best results: Control humidity first Improve ventilation Use an air purifier to reduce airborne exposure Air purifiers that help with airborne mould spores These HEPA air purifiers are designed to deliver strong airflow and capture fine airborne particles, including mould spores, while running quietly enough for everyday use in NZ homes. See Product See Product See Product Do air purifiers remove mould? No. Air purifiers don’t remove mould growing on surfaces, but they can help reduce airborne mould spores. Can an air purifier prevent mould from coming back? Not on its own. Preventing mould requires controlling moisture through ventilation or dehumidification. Is a dehumidifier better than an air purifier for mould? They serve different purposes. Dehumidifiers address the cause of mould (moisture), while air purifiers help reduce airborne spores. Can air purifiers help with mould-related allergies? They may help by reducing exposure to airborne spores, which can improve comfort for some people. Relevant Articles: The Best Air Purifiers in New Zealand: 2025 Comparison Read more Are Air Purifier & Dehumidifier Combo Units Effective? Read more The Best Air Purifiers for Asthma in New Zealand Read more

Asthma is one of the most common reasons people look into air purifiers. Whether it’s for themselves, their children, or other family members. While air purifiers aren’t a treatment for asthma, they can play a useful supporting role by reducing airborne triggers like dust, pollen, smoke, and fine particles that can worsen symptoms. This guide explains: How air purifiers can help with asthma What features actually matter Which types of purifiers tend to work best in NZ homes Quick Summary: Air Purifiers & Asthma Improving indoor air quality can help reduce exposure to common asthma triggers Typical indoor triggers include dust mites, pollen, pet dander, mould spores and fine particles Air purifiers work by continuously filtering airborne particles and recirculating cleaner air For asthma, HEPA filtration and sufficient CADR matter far more than extra features Effective air cleaning is usually much simpler than marketing makes it sound Ionisers and “active” tech often adds unnecessary risk and complexity Table of contents 1. Can air purifiers help with asthma 2. What actually matters in an air purifier for asthma 3. HEPA filtration and asthma 4. Sizing a purifier properly (room size → CADR) 5. Ionisers and why they're a concern for asthma 1. Can air purifiers help with asthma Asthma symptoms are often triggered or worsened by airborne irritants, including: Dust and dust-mite debris Pollen Pet dander Smoke and fine particulate matter (PM2.5) Air purifiers help by reducing the concentration of these particles in indoor air. This can make the home environment more comfortable, especially in rooms where people spend long periods of time. However, it’s important to keep expectations realistic: Air purifiers don’t replace medication or medical advice They work best as part of a broader asthma management approach Consistent use matters more than short bursts 2. What actually matters in an air purifier for asthma When choosing an air purifier for asthma, the fundamentals matter far more than advanced features or marketing claims. What to look for HEPA filtration to physically capture fine particles and irritants Enough cleaning power for your room size Quiet operation, so the purifier can run for long periods A simple, proven design without added technologies These factors determine whether a purifier can realistically keep indoor air cleaner throughout the day and night. Understanding CADR You’ll often see air purifiers described using a term called CADR, which stands for Clean Air Delivery Rate. In simple terms, CADR tells you: How much clean air a purifier can deliver per hour For asthma, CADR matters because airborne triggers are constantly being stirred back into the air as people move around the home. A purifier needs to clean the air repeatedly, not just once. A unit with too little CADR may technically filter the air, but not fast enough to make a noticeable difference. Why CADR matters for asthma: Allergens and irritants don’t stay settled. Walking, cleaning, opening doors, or sitting on furniture all reintroduce particles into the air. For asthma, it’s usually better to have: A purifier that cleans the air multiple times per hour Rather than one that cleans slowly but looks impressive on paper 3. HEPA filtration and asthma HEPA filters work by physically trapping particles as air passes through the filter. This includes dust, pollen, pet dander and fine particulate matter (PM2.5), which are common asthma triggers. You may see different grades mentioned (H11, H12, H13). Higher grades filter slightly finer particles, but in homes the combination of  HEPA filtration and sufficient CADR is what delivers the biggest benefit. A well-designed purifier with slightly lower HEPA grade but strong airflow (CADR) will always outperform a higher-grade filter paired with weak airflow. 4. Sizing a purifier properly (room size → CADR) One of the most common points of confusion when choosing an air purifier is sizing. Many purifiers advertise large room sizes, but those claims can be misleading. A more reliable way to size a purifier is to look at CADR, which stands for Clean Air Delivery Rate. This tells you how much clean air a purifier can deliver per hour. In simple terms, it reflects how quickly the purifier can reduce airborne particles in a room. Quick rule of thumb : Multiply your room size (m²) by 7.5 to estimate the minimum CADR you should aim for. For example: 20 m² room → 150 CADR 40 m² room → 300 CADR For people with asthma, higher air change rates can be especially helpful during flare-ups, smoky days, or pollen season. Why noise matters as much as sizing Asthma-friendly air cleaning usually means running a purifier for long periods, not just occasionally on high speed. This is where noise becomes important. Some purifiers quote very low noise levels only on their lowest setting - where airflow (and CADR) may be minimal. Others deliver useful airflow but are too loud to run consistently. In practice, the goal is a purifier that: Has enough CADR for the room Can be run on a lower, quieter speed while still cleaning the air effectively Many people deliberately choose a purifier that’s more powerful than they require, so it doesn’t need to run at full power to be effective. Smart Air SA600: A practical example for asthma-friendly air cleaning Designed to deliver meaningful airflow at low noise levels, while still having enough power for larger living spaces. Why it works well for asthma: Runs as quiet as 16 dB on low, suitable for bedroom usage Scales up to cover living areas up to around 65 m² Reaches 51 dB at full power when maximum airflow is needed Uses true HEPA filtration for dust, pollen and PM2.5 No ionisers or ozone-producing technologies Shop Smart Air SA600 5. Ionisers and why they're a concern for asthma Some air purifiers include ionisers, sometimes labelled as negative ion, plasma, or air sanitisation technologies. These features are often marketed as an upgrade - but they deserve extra caution, especially for people with asthma or allergies. Important: Some ionisation technologies can produce ozone as a by-product. Ozone is a known respiratory irritant and is generally something people with asthma should try to avoid. How ionisers actually work Ionisers don’t capture particles in the same way a filter does. Instead, they electrically charge particles in the air so they clump together or settle onto nearby surfaces. In practice, this means: Particle levels can drop faster in lab tests But particles aren’t always removed from the room They may end up on floors, furniture, or walls instead of in a filter For people managing asthma or allergies, this isn’t ideal, particularly when simpler, proven options exist. Why this matters for asthma For asthma-friendly air cleaning, the goal is to purify what you breathe in, not introduce new substances into the air. Because of this: Ionisers don’t replace proper filtration Any potential ozone by-product is an added concern The benefits are often unclear compared to HEPA-only designs You’ll also see ionisation features marketed under different names, and a number of models sold in New Zealand include them by default, even if they’re not clearly labelled as ionisers. Our general advice It’s best to avoid ioniser-based air purifiers altogether. If a purifier already includes one, we recommend ensuring the feature is switched off and relying on HEPA filtration alone. Learn more about ionisers and air purifiers The takeaway for asthma sufferers : Air purifiers can’t treat asthma, but they can help reduce airborne triggers indoors. The most effective options are those that are properly sized, quiet enough to run consistently, and focused on proven filtration rather than added technologies. Air purifiers designed to support asthma-friendly homes These HEPA air purifiers are designed to reduce airborne irritants like dust, pollen and smoke in real NZ homes. Quiet enough for bedrooms, powerful enough for living spaces. See Product See Product Do air purifiers help with asthma? They can help by reducing airborne triggers like dust, pollen and smoke, which may improve comfort for some people. Can air purifiers replace asthma medication? No. Air purifiers are a supporting measure and should not replace medical treatment or advice. How long should I run an air purifier for asthma? For best results, many people run purifiers continuously or for long periods, especially in bedrooms overnight. Are ionisers safe for asthma? Many people with asthma prefer to avoid ionisers, as some technologies can produce ozone or other by-products. Is one purifier enough for the whole house? Usually not. Targeting the rooms you spend the most time in is more effective. Relevant Articles: The Best Air Purifiers in New Zealand: 2025 Comparison Read more Ionisers Explained: Why We Don’t Use Them (and Why Some Brands Do) Read more Best Air Purifiers for Allergies (NZ Guide) Read more

Many people search for an air purifier for viruses after hearing claims about COVID, bacteria, or “air sanitising” technologies. The question is usually simple: do air purifiers actually help and if so, what kind works? The short answer is yes, a properly chosen HEPA air purifier can help reduce airborne particles that may carry viruses and bacteria. But it’s not a silver bullet, and not all purifier features contribute equally. In this guide we’ll cover: How air purifiers help with viruses and bacteria Why HEPA filtration and CADR matter most Common marketing claims to be cautious of How to size and use a purifier effectively Quick Summary: Air Purifiers for Viruses A HEPA purifier can help reduce airborne aerosols that may contain viruses and bacteria HEPA filters capture ultra-fine particles, including those smaller than 0.3 microns CADR (Clean Air Delivery Rate) determines how quickly air is cleaned Air cleaning helps most when used with ventilation + other layers (it’s not a standalone solution) Be cautious with “sanitising” add-ons like ionisation, ozone, plasma, and weak UV Table of contents 1. Do air purifiers help with viruses and bacteria? 2. HEPA filtration: clearing up a common misconception 3. CADR, room size, and air changes per hour (ACH) 4. How many air changes should you aim for? 5. Using an air purifier effectively 6. “Sanitising” add-ons: what to be cautious of 7. What air purifiers can't do 1. Do air purifiers help with viruses and bacteria? Viruses and bacteria don’t usually float around on their own. In indoor environments, they’re typically carried in respiratory aerosols. These are tiny particles released when people breathe, talk, cough, or sneeze. Air purifiers help by removing these airborne particles from the air, lowering the overall concentration that people are exposed to. The US EPA recognises portable air cleaners with HEPA filters as one way to help reduce airborne contaminants indoors, including in the context of COVID-19 - particularly when used alongside other measures like ventilation 2. HEPA filtration: clearing up a common misconception One of the most common misunderstandings about HEPA filters comes from how they’re described. You’ll often see HEPA filters defined as being 99.97% efficient at 0.3 microns, and some people interpret this to mean HEPA is less effective at capturing smaller particles. This includes viruses, which are often smaller - COVID for example is ~0.1 microns. In reality, this isn’t how HEPA filtration works. Why 0.3 microns is quoted According to the EPA, 0.3 microns is used because it’s the most difficult particle size for a HEPA filter to capture. That's known as the most penetrating particle size. Particles larger than this are easier to trap. Importantly, particles smaller than this are also captured even more effectively, due to diffusion. This is where ultra-fine particles move erratically and collide with filter fibres What this means in practice HEPA filters are effective at capturing ultra-fine and nanoscale particles Particles smaller than 0.3 microns are not “too small” for HEPA This applies to all genuine HEPA filters, not just specific brands Some purifier companies market their products as uniquely capable of capturing viruses or nanoparticles, implying other HEPA filters can’t. That’s marketing spin. Capturing ultra-fine particles is a core property of HEPA filtration itself, not a special add-on. The real differentiator isn’t whether a purifier can capture these particles, it’s how much air passes through the filter, which brings us to CADR. 3. CADR, room size, and air changes per hour (ACH) CADR (Clean Air Delivery Rate) tells you how much clean air a purifier can deliver per hour. In practical terms, it determines how often the air in a room can be cleaned, which depends on the size of the space. As the graphic above shows, the same purifier can achieve very different results in different rooms. In a smaller room, it may clean the air several times per hour. In a larger space, that same unit will clean the air less frequently. This is why relying only on “recommended room size” can be misleading. A more useful way to think about performance is air changes per hour (ACH). That's how many times the entire volume of air in a space is effectively filtered each hour. 4. How many air changes should you aim for? Ventilation guidance often references around 4 air changes per hour (ACH) in total as a reasonable baseline for reducing airborne risk. Most indoor spaces already achieve some air exchange through drafts, open doors, or mechanical ventilation. Because of this, we typically recommend aiming for at least ~3 ACH from air purification alone, with higher rates providing faster removal of airborne particles. This approach allows air purifiers to meaningfully reduce virus concentrations without needing to run constantly at full power. Higher air change rates can be especially helpful in: Busy or shared spaces Poorly ventilated rooms Periods of higher illness risk Why CADR matters more than "room size" labels HEPA determines what gets captured. CADR determines how quickly and how often the air is cleaned. Two purifiers with the same HEPA filter can perform very differently if one moves significantly more air than the other. This is why CADR is the most important number to compare when choosing an air purifier for viruses or bacteria. 5. Using an air purifier effectively Run the purifier while the room is occupied, not just occasionally Place it where air can circulate freely, rather than tucked into a corner or behind furniture In shared or higher-risk situations, positioning it closer to where people are breathing can help Use air purification alongside ventilation where possible Air purifiers are most effective when treated as part of a layered approach, rather than a standalone solution. A simple, proven approach for viruses and bacteria Key features: HEPA filtration for airborne aerosols High CADR for repeated air cleaning Quiet enough for continuous use No ionisers, ozone, or “sanitising” gimmicks Shop Smart Air SA600 6. “Sanitising” add-ons: what to be cautious of This is where purifiers for viruses marketing often gets confusing! Ionisers, plasma, and ozone-producing technologies Some purifiers use ionisation, plasma, or similar technologies that intentionally emit substances into the air. The EPA cautions that some of these technologies can generate ozone, which is a respiratory irritant. Even at relatively low levels, ozone can cause coughing, throat irritation, and chest discomfort. This is an emerging technology, and little research is available that evaluates it outside of lab conditions. As typical of newer technologies, the evidence for safety and effectiveness is less documented than for more established ones, such as filtration. Bipolar ionization has the potential to generate ozone and other potentially harmful by-products EPA: Air Cleaners, HVAC Filters, and Coronavirus (COVID-19) UV and germicidal technologies (GUV) Ultraviolet germicidal technologies can be effective when properly designed. The CDC and NIOSH discuss GUV as a useful tool in certain settings when exposure time, intensity, and placement are carefully engineered. However, inside most consumer air purifiers: Air moves through the unit very quickly UV exposure time is extremely short The system is often included to increase the price UV lights can also generate ozone In these cases, UV contributes far less than the HEPA filter itself. HEPA filtration already captures the airborne particles that may carry viruses, making UV unnecessary for most home and office use. “Active” and “sanitising” purification claims Some air purifiers are marketed using terms like “active purification”, “sanitising technology”, or “NASA-inspired” air treatment. These systems often advertise very large coverage areas, sometimes far exceeding what’s typical for conventional HEPA air purifiers. The difficulty with these products is transparency. Many don’t publish CADR figures, which are the standard way of comparing air purifier performance. CADR reflects how much clean air a unit actually delivers, making it possible to estimate air changes per hour and compare different models fairly. Instead, these systems often rely on proprietary technologies that are difficult to independently verify and in some cases are proven to be very exaggerated. Office Air Purifiers If you’re looking at air purifiers for shared office spaces, we’ve covered this in more detail in our guide to air purifiers for offices, including sizing, placement, and how to think about airflow in larger rooms. Office Air Purifiers Guide 7. What air purifiers can't do Air purifiers help with airborne particles. They don’t: Clean viruses off surfaces Replace ventilation Eliminate risk entirely They’re best understood as risk-reduction tools, not guarantees. Wrap-up: the honest takeaway: A properly sized HEPA air purifier with sufficient CADR can help reduce airborne particles that carry viruses and bacteria, including COVID-related aerosols. The most effective approach focuses on: Proven HEPA filtration Enough airflow to clean the air repeatedly Simple, continuous operation Using air cleaning alongside ventilation HEPA air purifiers for viruses and everyday indoor air These air purifiers focus on the fundamentals, HEPA filtration and strong airflow without ionisers, ozone, or unnecessary complexity. See Product See Product See Product Do air purifiers kill COVID-19? They’re better thought of as removing virus-carrying aerosols from the air, rather than killing viruses outright. What’s the best air purifier for viruses? One with HEPA filtration and enough CADR to deliver multiple air changes per hour in your space. Are ionisers safe to use for virus control? The EPA advises caution, as some ionising technologies can generate ozone and lack strong real-world evidence. Is UV worth it in a home air purifier? UV can work when properly engineered, but in most consumer purifiers it adds little compared to HEPA filtration. Relevant Articles: The Best Air Purifiers in New Zealand: 2025 Comparison Read more Boost Productivity | Top NZ Office Air Purifiers Read more Ionisers Explained | Why We Don’t Use Them (and Why Some Brands Do) Read more