How to Select Air Purifiers: CADR Calculation by Room Size

2026-11-13 15:16:16

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“ When picking an air purifier, CADR (Clean Air Delivery Rate) is the core indicator, showing how fast the unit removes particles, smoke and pollen. A higher CADR means faster cleaning. ”

When picking an air purifier, CADR (Clean Air Delivery Rate) is the core indicator, showing how fast the unit removes particles, smoke and pollen. A higher CADR means faster cleaning.

Here is the easy rule: We use ACH (air changes per hour), meaning how many times the machine renews all air in the room every hour. For daily use, 4–5 air changes per hour works well. To get your required CADR, calculate room volume first: Room Area × Ceiling Height × ACH

Take a standard ceiling height of 2.5m as an example: If your room is 20 m²: 20 × 2.5 × 4 = 200 m³/h CADR needed.

Note: CADR should not be the sole consideration. It is also necessary to evaluate filters working life(CCM), noise level, energy efficiency, and authentic third-party test reports. For newly renovated residences, priority should be given to formaldehyde CADR. Choose a purifier with CADR equal to or higher than this value. Pick a higher CADR if you have pets or heavy pollution.