CADR vs Room Size: How to Size an Air Purifier
Understand CADR, room volume, and air changes per hour before choosing an air purifier.
CADR is about clean air per minute
CADR stands for clean air delivery rate. A higher CADR means the purifier can move and filter more air each minute, which matters as rooms get larger or ceilings get taller.
Air changes per hour set the target
Air changes per hour describes how many times the room's air is filtered in an hour. Bedrooms and offices often feel reasonable around 4 to 5 ACH, while smoke, pets, or allergy situations may justify a higher target.
Round up for quieter operation
A purifier that barely meets the target may need to run on high. Rounding up can let the unit work on a lower, quieter speed while still cleaning the room effectively.