Air and cooling
Air purifier CADR and room size guide
Use clean air delivery rate, filter type, noise and replacement costs to compare air purifiers.
Updated 3 September 2026 · Independent general buying information
01
Use CADR as the starting point
Clean air delivery rate measures the volume of filtered air delivered over time. A higher CADR can clean the same room faster or serve a larger room, but manufacturer room-size claims may use different assumptions.
- Compare CADR in the same unit
- Measure the actual room
- Account for ceiling height
02
Check the complete filter system
A particle filter targets airborne particles. Activated carbon can help with some gases and odours. Check whether the replacement combines both layers and how often each part needs attention.
03
Noise matters at the speed you will use
Sleep-mode noise can be low because the fan is moving less air. Compare noise and CADR at useful operating speeds if the purifier will run in a bedroom or study.
04
Include replacement filters
The purchase price is only part of the cost. Check filter availability in Australia, the recommended replacement interval and the current replacement price before choosing a model.
Common questions
Frequently asked questions
What CADR do I need?
It depends on room volume and the air-change rate you want. Compare products using the same CADR unit and account for ceiling height.
Is a manufacturer's room-size claim enough?
No. Brands can use different assumptions. CADR and actual room volume provide a more consistent starting point.
Does activated carbon remove all odours and gases?
No. Carbon type, quantity, airflow and saturation affect performance, and it has finite capacity.