A common mistake is choosing a purifier that’s too small for the room it’s in. To work properly, a purifier needs to move enough air through its filter to keep up with the room’s volume. That’s where two key numbers come in: CADR (Clean Air Delivery Rate) and ACH (Air Changes per Hour).

• CADR tells you how much clean air a device delivers per minute. Higher CADR = faster and more effective filtration.
• ACH tells you how often a device can filter all the air in a room. For health needs, you want at least 4 to 6 air changes per hour.

To get the right match, check the room’s square footage and ceiling height, then compare it to the purifier’s specifications. Many manufacturers include a recommended room size based on CADR testing. As a general rule, aim for a unit that can deliver a CADR equal to two-thirds of your room’s square footage (e.g., for a 300 sq ft room, a CADR of 200+ is ideal).

Properly sizing your unit ensures you’re getting the full benefit of the technology—and not just moving air around without meaningful cleaning.