Expert Guide
Understanding CADR: The Complete UK Guide
Understanding CADR: The Complete UK Guide
What Actually Is CADR?
CADR stands for **Clean Air Delivery Rate**. It is the industry-standard metric (developed by AHAM in the US) that measures exactly how much filtered air a purifier can pump into a room per minute. Think of it as the "horsepower" rating of an air purifier. The higher the number, the faster it cleans. However, in the UK market, manufacturers often throw around different metrics—some use m³/h (cubic metres per hour), while others use CFM (cubic feet per minute). This can make direct comparisons confusing.
The "Two-Thirds" Rule for UK Rooms
A common mistake buyers make is trusting the "Recommended Room Size" written on the box. These figures are often based on running the machine at maximum speed (which is loud) or assuming only one air change per hour (which is useless). **The Golden Rule:** To get the CADR you actually need, take your room size in square metres (m²) and multiply it by 10 to get the minimum m³/h CADR for decent performance. For example: - **Small Bedroom (10m²):** Needs ~100+ m³/h CADR - **Master Bedroom (20m²):** Needs ~200+ m³/h CADR - **Open Plan Lounge (40m²):** Needs ~400+ m³/h CADR
CADR Reference Chart
Use this quick reference to check if a device is strong enough for your specific room.
| Room Type | Typical UK Size | Min CADR (m³/h) | Ideal CADR (m³/h) |
|---|---|---|---|
| Box Room / Office | 8-12 m² | 80 | 150+ |
| Double Bedroom | 12-18 m² | 120 | 250+ |
| Living Room | 20-30 m² | 200 | 350+ |
| Open Plan Floor | 40+ m² | 400 | 600+ |
Smoke vs. Dust vs. Pollen
You might notice three different CADR numbers on a spec sheet. This is because different particles behave differently: 1. **Smoke (Smallest):** The hardest to filter. This is usually the lowest number and the most important one to look at for health protection. 2. **Dust (Medium):** A good general indicator of fan power. 3. **Pollen (Largest):** Fastest to remove. If you only suffer from hay fever, you can rely on this number, but we recommend sticking to the Smoke rating to be safe.
The "Noise vs. Power" Trap
Here is the catch: CADR is measured at **maximum fan speed**. A cheap purifier might boast a high CADR of 300, but it might sound like a jet engine (60dB+) to achieve it. You probably won't run it at that speed while watching TV or sleeping. **Our Advice:** Look for a "High Efficiency" model (like the Coway Airmega or Levoit Core S-series) that maintains a decent solid airflow even on medium/quiet settings. Often, buying a larger unit and running it on low is quieter and more effective than running a small unit on high.
High-CADR Pick for Large Rooms
Levoit Core 400S Smart True HEPA Air Purifier
If you need serious power for a large UK lounge or open-plan kitchen, the Levoit Core 400S offers an exceptional CADR of 400 m³/h without costing a fortune.
Coverage
83 m²
Running Cost
£49 / yr
Summary
Don't get hung up on buying the highest number possible if it breaks your budget. For a standard British bedroom, a CADR of 150-200 m³/h is perfect. For a main living space, aim for 350+ m³/h. Always check the noise levels, and remember: fresh air shouldn't sound like a runway.
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