Calculate metric CADR from real room volume and target ACH, then test a candidate purifier, high-ceiling context and multiple-unit plan without product bias.
What CADR does my room need, and will one air purifier reach the target ACH?
Multiply room volume by the target air changes per hour to get required CADR in m³/h. Divide the candidate's combined CADR by room volume to check achieved ACH, then round the unit count up—not the room claim down.
Method
The result keeps three different concepts separate: your volume-based target, the candidate's achieved ACH, and AHAM's certified room-area context based on an 8-foot (2.4 m) ceiling.
Important limitation
This is general particle-filtration equipment sizing, not medical, infection-risk, gas/VOC or whole-home ventilation advice. CADR is commonly measured at the highest speed and real mixing, doors and filter loading can reduce performance.
How to use the result safely
Treat this as a transparent planning ledger. Recheck every measured value, keep a margin for real installation conditions, and stop before spending when the exact first-party rule is missing.
