What CADR means
AHAM's Clean Air Delivery Rate has separate scores for tobacco smoke, pollen and dust. A higher CADR means the unit cleans the air faster. For pollen allergies, look at the pollen CADR as well as the smoke figure.
The two-thirds rule
AHAM's rule of thumb: the CADR of your air cleaner should be at least two-thirds of the room's area in square feet. A 10 by 12 ft room (120 sq ft) needs a smoke CADR of at least 80.
For wildfire smoke, AHAM recommends a smoke CADR equal to the room's area. If your ceilings are higher than 8 feet, choose a unit rated for a larger room.
Work out your number with the air purifier size calculator.
Look for the AHAM Verifide mark
The mark, usually on the side or back of the box, shows the CADR was independently tested. A bigger CADR than you need simply cleans the air more often.
Quick sizing table (8 ft ceilings)
| Room | Area | Minimum CADR (2/3 rule) | Wildfire smoke CADR |
|---|---|---|---|
| 10 x 10 ft | 100 sq ft | 67 | 100 |
| 10 x 12 ft | 120 sq ft | 80 | 120 |
| 12 x 12 ft | 144 sq ft | 96 | 144 |
| 12 x 14 ft | 168 sq ft | 112 | 168 |
| 14 x 16 ft | 224 sq ft | 150 | 224 |
| 16 x 20 ft | 320 sq ft | 214 | 320 |
| 20 x 20 ft | 400 sq ft | 267 | 400 |
Other tips
- Run it in the room where you spend the most time, often the bedroom.
- AHAM Verifide replacement filters are tested to match the original maker's filter.
- Keep doors and windows closed while it runs so it isn't working against outside air.
Source: AHAM Verifide, "Air Filtration Standards" (last modified Nov 11, 2025).
