Condensation on the windows every July morning, hay fever every spring, and smoke haze drifting over the suburbs most summers — Australian homes give an air purifier plenty to do. The catch is that an undersized or badly filtered unit mostly just moves air around, so the specs you check before buying matter more than the brand on the box.
This guide covers the numbers worth reading — CADR, filter grades, replacement costs and night-time noise — then runs through the purifiers we currently have in stock, from a $56.00 compact combo unit to a full-sized Coway.
How to choose an air purifier
Start with CADR, not the room-size claim
CADR (clean air delivery rate) tells you how many cubic metres of air a purifier cleans per hour, and it is the single most useful number on a spec sheet. Room-size claims are often calculated on one air change per hour, which is fine for a lightly used space but nowhere near enough during a pollen surge or a smoke event, where you want four to five changes per hour.
A quick rule for standard 2.4 m ceilings: multiply the room's floor area in square metres by 12 to get the CADR in m³/h you need for roughly five air changes per hour. A 20 m² bedroom needs about 240 m³/h; a 40 m² open-plan living area needs closer to 480 m³/h. If a listing only quotes a room size, halve it for a realistic working figure.
HEPA H13 beats washable filters where it counts
A true HEPA H13 filter captures 99.95% of particles at the hardest-to-catch size, around 0.3 microns. That covers pollen, dust-mite debris, pet dander, mould spores and the fine particulates in bushfire smoke. Washable "HEPA-style" filters sound economical, but their capture rates sit well below genuine HEPA and drop further with each wash.
The best setups use both: a washable pre-filter to catch hair and lint (which extends the life of the expensive filter behind it), a replaceable H13 HEPA layer for fine particles, and an activated carbon layer for odours and VOCs. The 4- and 5-stage Kogan units below are built this way.
Winter mould and condensation: fix the moisture too
A purifier captures mould spores floating in the air, which reduces the musty smell and the allergy load. What it can't do is stop mould growing, because growth is driven by moisture — cold single-glazed windows, unvented bathrooms, clothes drying inside through winter. If a room stays damp, pair filtration with dehumidifying, either as two machines or a 2-in-1 unit, and aim to keep indoor humidity below about 60%. For the damp back bedrooms common in older Sydney and Melbourne houses, the combo units in our picks are the more sensible buy.
Allergies and bushfire smoke
The PM2.5 particles in bushfire smoke are precisely what HEPA filtration is designed for. During a smoke event, close the house up, run the purifier on high in the room you're occupying, and let the CADR do the work — this is where buying a size up pays for itself. The smoky smell is a gas rather than a particle, so a unit with an activated carbon stage handles it far better than HEPA alone. For hay fever, leave the purifier on auto mode year-round rather than switching it on after symptoms start; it takes time to bring a room's particle count down.
Budget for filters, not just the purchase price
H13 filters typically need replacing every 6 to 12 months depending on run time and how dirty your air gets. From current stock, a Kogan SmarterHome Air Purifier H13 HEPA Filter is $64.00, and the larger Replacement H13 HEPA Filter for the Kogan SmarterHome Air Purifier 5 Pro is $104.00. Over three years of steady use, filters can cost as much as the machine did, so check the replacement price before you commit. Vacuuming the pre-filter monthly stretches every HEPA filter noticeably further.
Noise: check the low-speed figure
Purifier listings tend to quote either the quietest or the loudest speed, so read carefully. For a bedroom, the number that matters is sleep or low mode — under about 30 dB is quiet enough for most sleepers, while 50 dB and up is conversation-level and hard to ignore at 2 am. This is another argument for buying more capacity than the room strictly needs: a bigger unit can idle along on its lowest, quietest speed overnight and still keep up.
Our picks from current stock
Bedrooms and small rooms
- Kogan SmarterHome Air Purifier — $121.60 (was $158.08). A compact unit with a genuine H13 HEPA filter at a modest price. Suits a bedroom or study, and a sensible first purifier for hay fever sufferers who want quiet overnight running without a big outlay.
- Kogan SmarterHome 5-Stage Air Purifier 3S & Replacement Filter — $129.20 (was $167.96). Five filtration stages plus a spare filter in the box, so the first year or two of running costs are already covered. Suits set-and-forget buyers who don't want to think about consumables for a while.
Living rooms and medium spaces
- Kogan SmarterHome Air Purifier 3 Pro — $194.56 (was $252.93). The step-up model for a lounge or combined kitchen-living space. Suits households with pets or dusty conditions that need more airflow than a bedroom unit can deliver, with replacement filters at a reasonable $80.00.
Large and open-plan areas
- Kogan SmarterHome Air Purifier 5 Pro with H13 HEPA Filter — $270.56 (was $351.73). Kogan's biggest purifier here, built for open-plan areas where smaller units run flat out and still fall behind. Suits allergy households wanting one machine to cover the main living zone.
- Coway Airmega 200M Air Purifier — $421.04 (was $547.35, a saving of over $547.35). Coway is one of the most established names in air purification, and the 200M pairs HEPA filtration with a carbon deodorising layer. Suits buyers who want a proven brand for smoke season and are happy to pay for it.
Damp rooms and winter condensation
- Kogan SmarterHome 2-in-1 Dehumidifier and Air Purifier with HEPA 13 Filter — $56.00 (was $72.80). A small-footprint combo that pulls moisture from the air while filtering it. Suits wardrobes, ensuites, caravans and small bedrooms where winter condensation is the main complaint.
- Devanti Dehumidifier 2L Air Purifier White — $90.98 (was $141.99, close to half price). A 2-litre tank means fewer trips to empty it than most compact combos. Suits laundries and damp spare rooms that need steady moisture removal with filtration as a bonus.
Quick comparison
| Product | Best for | Price |
|---|---|---|
| Kogan SmarterHome 2-in-1 Dehumidifier and Air Purifier | Small damp spaces on a budget | $56.00 |
| Devanti Dehumidifier 2L Air Purifier White | Laundries and damp spare rooms | $88.98 |
| Kogan SmarterHome Air Purifier | Bedrooms, first purifier | $121.60 |
| Kogan SmarterHome 5-Stage 3S + spare filter | Set-and-forget small rooms | $129.20 |
| Kogan SmarterHome Air Purifier 3 Pro | Living rooms, pet households | $224.96 |
| Kogan SmarterHome Air Purifier 5 Pro | Open-plan living areas | $270.56 |
| Coway Airmega 200M | Premium pick, smoke season | $405.84 |
Air purifier questions, answered
Will an air purifier get rid of mould?
It will capture airborne mould spores, which helps with the smell and with allergy symptoms, but it won't kill mould already growing on a wall or ceiling. Clean existing mould off surfaces, reduce the moisture source, and use the purifier (or a dehumidifier-purifier combo) to keep spore counts down afterwards.
What should I look for if bushfire smoke is my main concern?
Two things: a genuine HEPA filter (H13 rather than "HEPA-type") for the PM2.5 particles, and an activated carbon stage for the smell. Size the unit generously — during a heavy smoke day you want the highest CADR you can afford running in the room you spend the most time in.
How often do HEPA filters need replacing?
Most manufacturers suggest 6 to 12 months. Run time, pets, and events like smoke days all shorten that. Many units have a filter indicator, but a visual check works too — if the white filter media has gone grey or brown, replace it. Budget $52.50 to $104.00 per filter across the Kogan range in stock.
Is it safe to run an air purifier all night?
Yes — overnight running in a closed bedroom is arguably when a purifier earns its keep, especially for allergy sufferers. Use sleep or low mode, check the unit's low-speed noise figure sits around 30 dB or below, and pick a model with a display-off option if you're sensitive to standby lights.
The short version
Match CADR to your room using the floor-area-times-12 rule, insist on real H13 HEPA if allergies or smoke are the reason you're buying, and price the replacement filters before you choose. If winter damp is the actual problem, put your money into a dehumidifier combo instead of a bigger purifier. Everything above ships from our Sydney warehouse, and you can browse the full range alongside 25,000+ other products in the complete Auzzi Store catalogue.
Prices correct at publication and may change. Stock levels update daily.