What is CFM (airflow)?
In one line: CFM is cubic feet per minute — how much air a purifier's fan moves. It's closely related to CADR (clean-air delivery rate), and it's why airflow matters as much as the filter: a great filter with weak airflow cleans a room slowly.
What it measures
CFM is the raw volume of air the fan pushes through the unit each minute. More CFM means more air passes through the filters in a given time — and therefore a room's air is turned over faster. (Metric equivalents are m³/h or m³/min; 1 CFM ≈ 1.7 m³/h.)
CFM vs CADR
They're linked but not identical. CFM is total airflow; CADR is airflow times filter efficiency — i.e. the volume of genuinely clean air delivered. A unit can have high CFM but mediocre CADR if the filter lets particles through, or if the headline CFM is measured with no filter fitted. CADR is the more honest single number for comparing purifiers; treat CFM as the airflow behind it. This is the same reason a high-airflow MERV-13 can out-clean a low-airflow HEPA.
Why airflow matters
Cleaning a room is airflow × efficiency × time. You need enough CFM to achieve a good air-change rate for the room's size — otherwise even a perfect filter can't keep up. When comparing units, look at CADR for your room volume first, and check whether quoted airflow is on the highest (loudest) speed.
Next step
Match airflow to your room — see units and their ratings in the CleanAirKits store.
FAQ
Is higher CFM better on an air purifier? More airflow cleans faster, but only if paired with a good filter — that's what CADR captures. Compare CADR for your room, not CFM alone.
What CFM do I need? Enough to give your room a good air-change rate — easiest to judge via CADR sized to the room's floor area/volume.