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TL;DR — Buy for the room, not the house. One oversized purifier in the bedroom beats three small ones scattered around.
Most air purifier disappointment comes from one mistake: buying a unit rated for a large room and expecting it to clean an entire floor.
Sizing: the only number that matters
CADR (Clean Air Delivery Rate) tells you how much clean air a unit delivers per minute. A rough rule for allergy sufferers:
Required CADR (m³/h) ≈ room area (m²) × ceiling height (m) × 5
That "× 5" assumes you want five air changes per hour, which is what allergy guidance generally recommends. A 20 m² bedroom with 2.5 m ceilings needs about 250 m³/h of CADR.
| Room | Area | Recommended CADR | Typical noise on high |
|---|---|---|---|
| Bedroom | 15–20 m² | 200–250 m³/h | Under 45 dB |
| Living room | 30–40 m² | 450–600 m³/h | 50–58 dB |
| Home office | 10–12 m² | 150–180 m³/h | Under 40 dB |
Picks below are compiled from manufacturer CADR ratings and filter prices — no lab testing on our side.
1. Best for bedrooms — Levoit Core 300S
The default answer for a bedroom: quiet enough to sleep next to, proper HEPA filtration, and a display that dims fully at night.
- CADR: ≈ 187 m³/h (manufacturer figure)
- Noise on low: ≈ 24 dB (effectively silent)
- Filter: H13 HEPA + activated carbon, replace roughly yearly (≈ $30)
- Typical price: ≈ $100
2. Best for medium rooms — Coway Airmega AP-1512HH Mighty
A long-time reference model: strong CADR for its size, an air-quality indicator that is actually calibrated, and eco mode that idles when the air is clean.
- CADR: ≈ 420 m³/h (manufacturer figure)
- Filter: HEPA + odour carbon, replace yearly (≈ $50)
- Typical price: ≈ $170
3. Best value for large rooms — Winix 5500-2
Big-room CADR at a mid-room price, with a washable pre-filter that catches pet hair before it reaches the HEPA layer.
- CADR: ≈ 390 m³/h (manufacturer figure)
- Filter: true HEPA + washable carbon sheet, replace yearly (≈ $60)
- Typical price: ≈ $160
4. Best for very large rooms — Levoit Core 600S
Open-plan living rooms need this class: high CADR without jet-engine noise on medium settings, plus app scheduling so it ramps up before you get home.
- CADR: ≈ 600 m³/h (manufacturer figure)
- Filter: H13 HEPA + carbon, replace yearly (≈ $60)
- Typical price: ≈ $300
What actually helps allergy symptoms
- True HEPA (H13 or H14) — "HEPA-like" and "HEPA-type" filters are not the same thing
- Run it continuously on low rather than in bursts on high
- Replace filters on schedule — a saturated filter stops capturing particles
- Keep windows closed on high-pollen days; purifiers cannot keep up with an open window
- Bedroom first — you spend eight hours breathing that air
Features you can skip
- Ionisers (limited benefit, some produce ozone)
- "Smart" air quality scores that are not calibrated
- UV-C lights — residence time in most units is too short to matter
Editorial note. This guide is compiled from official product documentation and practical buying checklists, not hands-on testing. Verify specifications and current pricing with the manufacturer before you buy. See our affiliate disclosure for how we fund this work.
