What is CADR?
Clean Air Delivery Rate (CADR) is a measure of how much particle-reduced air an air cleaner delivers. It combines airflow and particle-removal effectiveness into a single clean-air flow quantity.
Typical units: cfm in U.S. consumer specifications; m³/h can also be used after unit conversion.
Smoke CADR is pollutant-specific
Air cleaners may publish separate CADR values for smoke, dust and pollen. For wildfire-smoke planning, use the smoke/tobacco-smoke CADR when that is the comparable published metric.
EPA room-sizing rule
For an 8-ft ceiling, EPA wildfire-smoke guidance recommends a tobacco-smoke CADR of at least 2/3 of room area in square feet. EPA also notes that higher ceilings require a larger device. EPA research cites a stronger AHAM planning screen of CADR approximately equal to room area.
CADR and equivalent ACH
Equivalent clean-air ACH = CADR × 60 / Room Volume when CADR is in cfm and room volume is in ft³.
Worked example
A 120 ft² room with an 8-ft ceiling has a volume of 960 ft³. An 80 cfm smoke CADR corresponds to 5 equivalent clean-air ACH: 80 × 60 / 960 = 5.
Do not size by marketing room area alone
Published room-size claims can be based on different ACH assumptions. CADR plus actual room volume makes the engineering basis explicit.
Related concepts and tools
Air Changes per Hour · PM2.5 · Building Infiltration · Wildfire Smoke Air Purifier Size Calculator · Air Purifier Buying Guide
Technical references
US EPA — Preparing for Smoke and Heat
US EPA — Air Cleaner CADR Research
Tecnobosque Reference Concept · reviewed September 2026. Compare like-for-like smoke CADR values and preserve the room-volume assumptions behind sizing.