Fix the source first
- Source. Stop the pollution where it starts. A rangehood beats a purifier.
- Ventilate. Let fresh air in when the outdoor air is good.
- Filter. A purifier catches what's left.
Common sources
Gas cooktops Purifier: partly
Gas gives off nitrogen dioxide, which purifiers can't remove. Research links about 12% of childhood asthma in Australia to gas cooking. Fix: a rangehood that vents outside, switched on before you start. Use the back burners.
Wood heaters Purifier: yes
Smoke escapes every time you reload. Fix: burn only dry wood, keep the fire hot rather than damped down overnight, and have the flue cleaned each year.
Mould and damp Purifier: partly
Common in bathrooms, laundries and wardrobes on outside walls. One in four Australian homes has a damp problem. Fix: repair leaks, run exhaust fans, and keep humidity under 60%.
New furniture, paint and sprays Purifier: partly
They release chemicals such as formaldehyde, mostly when new. Fix: air new furniture out for a few days, use low-VOC paint, and skip air fresheners.
Candles, incense and cooking Purifier: yes
Some of the biggest indoor particle spikes. Fix: rangehood on, and fewer candles in bedrooms.
Dust mites and pets Purifier: partly
Fix: wash bedding weekly at 60°C, use a HEPA vacuum, and keep pets out of bedrooms if anyone's allergic.
Stale air Purifier: no
A closed bedroom can pass 1,500 ppm of carbon dioxide overnight, against about 420 outdoors. Fix: open the window a crack or leave the door ajar.
What a purifier can fix
| Problem | HEPA | Carbon | Best fix |
|---|---|---|---|
| Smoke particles | Yes | Smell | Close up, purifier on |
| Pollen, pet dander | Yes | No | Purifier and cleaning |
| Mould spores | Yes | No | Fix the damp |
| Gas (nitrogen dioxide) | No | Barely | Rangehood or induction |
| VOCs, formaldehyde | No | Some | Ventilation |
| Carbon dioxide | No | No | Fresh air |
| Humidity | No | No | Exhaust fans, dehumidifier |
Airing the house
- Open up when the outdoor reading is good. Check the live reading on hazy days.
- On summer afternoons, let the sea breeze through.
- Evaporative coolers ventilate well on clean days. Turn them off when it's smoky.
- Check your bathroom fan vents outside, not into the roof space.
Cheap ways to measure
- PM2.5 monitor: shows cooking and candle spikes, and whether the purifier is keeping up.
- CO2 monitor: buy one with an NDIR sensor. Cheaper “eCO2” ones only guess.
- Humidity gauge: above 60% for long spells means mould risk.
Renting?
- Report leaks, mould and broken fans in writing.
- No proper rangehood? Use the back burners, open a window, or cook on a plug-in induction hotplate.
Sources
- Knibbs L.D. et al. (2018). Damp housing, gas stoves, and childhood asthma in Australia. Medical Journal of Australia.
- National Asthma Council: Gas stoves and asthma in children.
- US EPA: Guide to air cleaners in the home.
- Mortality burden of wood heater smoke in Australia (2024). Science of the Total Environment.
General information, not medical or building advice.