The Best Air Purifiers for Asthma in New Zealand
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
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
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.
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.
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.
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