What Is CADR? UK Guide to Air Purifier Performance in m³/h
Updated: October 2026 · Prices checked 17 Oct 2026
CFM to m³/h Conversion Table for 12 UK Hero Models
This table is the primary reference for UK buyers reading US product listings. All figures are at rated (maximum) fan speed. Source is noted for each model — "converted from AHAM CFM" means the m³/h figure was calculated from the AHAM-published CFM rating using the 1.699 conversion factor. "Manufacturer (m³/h)" means the brand publishes m³/h directly.
| Model | Smoke CADR (m³/h) | Dust CADR (m³/h) | Pollen CADR (m³/h) | Source | Room (3 ACH) |
|---|---|---|---|---|---|
| Levoit Core 200S | 161 | 166 | 165 | Converted from AHAM CFM | 8 m² |
| Levoit Core 300S | 240 | 246 | 246 | Converted from AHAM CFM | 12 m² |
| Levoit Core 400S | 372 | 375 | 374 | Converted from AHAM CFM | 25 m² |
| Coway Airmega Mighty | 418 | 418 | 408 | Converted from AHAM CFM | 27 m² |
| Coway Airmega 150 | 277 | 277 | 277 | Converted from AHAM CFM | 18 m² |
| Blueair Blue Max 3250i | 239 | 239 | 239 | Manufacturer (m³/h) | 33 m² |
| Blueair Blue Pure 211i Max | 697 | 697 | 697 | Conv. AHAM 410 CFM × 1.699 | 97 m² |
| Blueair Blue Pure Mini Max | 130 | 130 | 130 | Manufacturer (m³/h) | 9 m² |
| Shark NeverChange5 HP072UK | 340 | 340 | 340 | Converted from AHAM CFM | 22 m² |
| Philips 3200 AC3220 | 350 | 350 | 350 | Manufacturer (m³/h) | 24 m² |
| Philips 2200 AC2220 | 420 | 420 | 420 | Manufacturer (m³/h) | 58 m² |
| Philips 600 AC0651 | 190 | 190 | 190 | Manufacturer (m³/h) | 13 m² |
Room-Size Table at 2, 3, and 5 ACH for Typical UK Rooms
The formula behind the CADR calculator: CADR required = room volume (m³) × air changes per hour (ACH). The table below shows the required CADR for common UK room types at three ACH targets — 2 ACH (basic), 3 ACH (standard), and 5 ACH (allergy-grade).
| Room type | Floor area | Ceiling height | Volume (m³) | 2 ACH (m³/h) | 3 ACH (m³/h) | 5 ACH (m³/h) |
|---|---|---|---|---|---|---|
| Box room / small single | 8 m² | 2.4 m | 19.2 m³ | 38 | 58 | 96 |
| Double bedroom (modern) | 13 m² | 2.4 m | 31.2 m³ | 62 | 94 | 156 |
| Double bedroom (Victorian) | 13 m² | 2.7 m | 35.1 m³ | 70 | 105 | 176 |
| Living room (terraced house) | 18 m² | 2.4 m | 43.2 m³ | 86 | 130 | 216 |
| Open-plan kitchen / living | 30 m² | 2.4 m | 72.0 m³ | 144 | 216 | 360 |
To calculate for your specific room, use the room size tool — enter floor area and ceiling height, choose your ACH target.
What CADR Measures — and What It Doesn't
CADR measures the volume of air — cleaned of a specific pollutant type — that a purifier delivers per hour at its rated (maximum) fan speed. The AHAM test protocol measures three pollutant types separately: tobacco smoke (fine particles), household dust (medium particles), and pollen (large particles).
What CADR does not measure:
- Performance at reduced fan speeds. CADR is always at maximum. A machine running at sleep speed may deliver 30–60% of its rated CADR — but no manufacturer in the current UK market publishes this figure.
- Gas and VOC removal. CADR measures particles. Carbon filter effectiveness for volatile organic compounds, smoke odour, and cooking smells is not captured by CADR at all.
- Long-term filter performance. CADR is measured on a new filter. Performance degrades as the filter loads with particles over time.
- Virus or bacteria capture. CADR does not address biological contaminants. Some high-efficiency filters capture particles of the relevant size, but this is not what CADR certifies.
EN 1822 vs AHAM vs Manufacturer CADR: Which to Trust
AHAM CADR (US standard)
Measured at rated speed, three pollutant types (smoke, dust, pollen). Conducted by AHAM-accredited third-party labs. Most US-origin models (Levoit, Coway, Shark) publish AHAM CADR. The most widely available, independently verified CADR standard for the models in this comparison.
Trust level: High — third-party verified
Manufacturer CADR (m³/h direct)
Some brands (Blueair, Philips) publish m³/h figures directly without AHAM certification. These may use different test protocols — test conditions, particle sizes, and room sizes can differ from the AHAM standard. Always note the source when citing manufacturer figures.
Trust level: Medium — self-certified; check test protocol details
EN 1822 — HEPA filter grade
EN 1822 is the European standard for high-efficiency particulate air (HEPA) filter grading — it grades the filter at H10 through H14, based on particle capture efficiency at 0.3 µm. EN 1822 grades the filter, not the purifier's room-cleaning rate. A purifier with EN 1822 H13 certification has a tested filter; it does not have a tested CADR. The two measurements serve entirely different questions.
Trust level: High for filter efficiency — not a CADR substitute
Why US CFM Figures Mislead UK Buyers
The US retail market uses cubic feet per minute (CFM) as the standard CADR unit. UK Amazon listings for US-origin models (Levoit, Coway, Shark) frequently show both the US CFM figure and — sometimes — an m³/h conversion. The problem: the m³/h conversion is not always present, and when room-size claims are made using CFM-derived calculations, the conversions are occasionally inconsistent.
The specific misleading pattern: US room-size claims are often based on 1 ACH (one air change per hour) — a standard set for the US market by AHAM. UK guidance and EU recommendations use 2–3 ACH as the minimum for effective air cleaning. A model marketed as "suitable for 46 m²" in the US (1 ACH claim) covers roughly 15 m² at 3 ACH with the same ceiling height. This is the most common source of confusion when UK buyers read US product descriptions.
The conversion is straightforward: multiply US CFM by 1.699 to get m³/h. Then apply your ACH target using the room-size table above or the room sizing calculator.
For running cost comparisons across UK models, see our air purifier running cost guide. For the best-performing models across all categories, see the best air purifier UK guide.