Air Quality
Indoor Air Is Often More Polluted Than Outdoor Air
We spend up to 90% of our time indoors — but most of us have never thought about what we’re breathing. Here’s what’s actually in the air in your home, and what to do about it.
Why This Matters More Than Most People Realise
The air outside in most Australian cities is reasonably clean. But outdoor air can move and disperse. Indoor air sits still, recirculates, and builds up.
Modern homes are built more airtight than ever — which is great for energy efficiency, but it traps what’s already inside. Cooking fumes, cleaning product residue, off-gassing from furniture and carpet, mould, dust mite waste, pet dander — these all accumulate in an enclosed space.
Add bushfire season, and Australians face an air quality challenge that most other countries don’t have to think about.
The 3 Types of Indoor Air Pollutants
Indoor pollutants split into three categories. Understanding which type you’re dealing with tells you which solution actually works.
Dust, pollen, mould spores, pet dander, smoke particles, dust mite waste. These are physical particles floating in the air. HEPA filtration captures them.
Volatile organic compounds from cleaning products, new furniture, paint, cooking fumes, and air fresheners. These are gases, not particles — HEPA doesn’t capture them. Activated carbon does.
Bacteria, viruses, mould spores. A True HEPA filter (H13 grade) captures these. This category matters most in households with young children, elderly people, or anyone with respiratory conditions.
“Most people buy a purifier for particles but their biggest problem is VOCs — especially in a recently renovated or newly furnished home. Getting both HEPA and carbon filtration isn’t a nice-to-have, it’s the baseline.”
What HEPA Actually Means (And What It Doesn’t)
HEPA is probably the most misunderstood term in the air purifier market. Here’s what it actually means:
True HEPA H13 — the standard that matters
A True HEPA H13 filter captures 99.95% of particles at 0.3 microns. For reference, a human hair is about 70 microns wide. These filters are capturing things that are completely invisible to the naked eye.
- H11/H12 filters — marketed as HEPA but have lower capture rates. Not sufficient for health purposes.
- H13 filters — the standard used in hospital-grade filtration. This is what you want.
- “HEPA-like” or “HEPA-style” — these aren’t HEPA. They’re marketing terms with no defined standard.
The carbon layer in a good purifier works alongside the HEPA filter — it adsorbs gases and VOCs that the HEPA layer physically can’t capture. If your purifier doesn’t have both, it’s handling one category of pollutant and letting the other pass through.
How To Size A Purifier For Your Room
Getting the right size is more important than getting the most expensive model. An undersized purifier running constantly is less effective than a correctly sized one on its auto setting.
The number to focus on is CADR — Clean Air Delivery Rate. It measures how quickly a purifier cleans a room, expressed in m³/h.
| Room | Typical Size | CADR You Need |
|---|---|---|
| Bedroom | 12–18 m² | 150–250 m³/h |
| Living room | 25–40 m² | 300–450 m³/h |
| Open plan | 50+ m² | 500+ m³/h (or two units) |
“For Australian households during bushfire season, size up. Aim for a unit that turns over the room’s air volume at least 4–5 times per hour rather than the standard 2–3.”
Bushfire Season Tip
During bushfire season, PM2.5 levels inside can spike 10–20× above normal — even with windows closed. If you’re in a high-risk area, size up to a unit rated for a room twice your actual size.
Run it on high for the first 30 minutes when smoke is visible outdoors, then drop to medium for continuous overnight protection.
Not sure which purifier to choose?
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3 Steps To Cleaner Air At Home
Start with the bedroom
You spend 7–9 hours in your bedroom every night — it’s the room where clean air has the most cumulative impact. A mid-range purifier with H13 HEPA + carbon filtration, correctly sized for the room, is the highest-leverage purchase you can make.
Reduce the source before you filter it
An air purifier treats the symptom. Switching to fragrance-free cleaning products, choosing low-VOC paint and furniture, and keeping humidity below 60% to prevent mould — these reduce the problem at the source, which is always better than filtering after the fact.
Have a bushfire season plan
When AQI is in the hazardous range, keep windows and doors shut and run your purifier on its highest setting. Replace your HEPA filter after a major smoke event — capacity drops significantly after sustained heavy particulate load.
Top Pick — Bedrooms & Living Rooms
Breville the Smart Air Connect
H13 HEPA + activated carbon. Real-time AQI display. Tested through Australian bushfire seasons. Covers rooms up to 40m² and handles both PM2.5 smoke particles and VOC gases.
See on Amazon → Compare all purifiers →All Air Quality Articles
HEPA ratings, CADR benchmarks, and Australian bushfire season tested.
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