Air Purifiers · Guide
What is CADR?
CADR (Clean Air Delivery Rate) measures how much clean air a purifier produces per minute. Unlike almost any other number on a purifier's box, it isn't just handed to you by the manufacturer — it's independently verified by AHAM (the Association of Home Appliance Manufacturers), which makes it one of the few performance figures you can genuinely compare between brands.
What it does measure
- Volume of clean air delivered per minute (in CFM, cubic feet per minute)
- Independently verified by AHAM through a standardized test protocol (AHAM AC-1)
- Comparable between manufacturers, unlike most figures on the box
- Verified separately for smoke, dust and pollen — these can differ
What it doesn't measure
- Odors or gases — that's down to the carbon filter, not CADR
- Running cost or filter replacement frequency
- Noise level at the speed needed to reach that CADR
- Whether the machine itself is correctly sized for your room
The real CADR of the 4 purifiers in our ranking
- Levoit Core 400S — 260 CFM, AHAM-verified. Covers around 403 sq ft — a normal bedroom or living room.
- Coway Airmega AP-1512HH — 233 CFM. Limited to around 361 sq ft — a bedroom, not an open living-room-and-kitchen.
- Coway Airmega 400 — 350 CFM. The only one of the four genuinely sized for over 1,000 sq ft.
- Honeywell HPA300 — the only one of the four with a specifically documented smoke CADR: 300 CFM, the highest on the list under $250 — what matters during a wildfire event.
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Frequently asked questions
Does a higher CADR always mean better air quality?
Only if the machine is correctly sized for your room. Beyond the EPA guideline (a CADR of at least two-thirds of your floor area), a higher CADR than you need doesn't improve anything — it just clears the air faster than necessary, in exchange for more noise and higher running cost. The Coway Airmega 400 (350 CADR) is a waste of money in a small bedroom; the same machine is the only sensible choice in a large open-plan space.
Is CADR the same for smoke, dust and pollen?
AHAM verifies CADR separately for three particle types — smoke, dust and pollen — and they often differ from each other. In our data, only the Honeywell HPA300 documents a specific smoke CADR figure (300 CFM); the other three purifiers in our ranking report a single combined CADR figure rather than breaking it out by particle type.
Why trust CADR over a "covers up to X sq ft" claim?
Because AHAM is an independent body that verifies CADR through a standardized test protocol (AHAM AC-1), so the number is genuinely comparable between manufacturers. "Covers up to X sq ft" is a figure each brand calculates its own way, with no outside verification — it's marketing copy, not a lab result.
How do I work out the CADR I need for my room?
The EPA guideline is a CADR of at least two-thirds of your room's square footage. To do this with your own room and see all four purifiers in our ranking side by side, use our CADR calculator.
Work out the exact CADR your room needs with our CADR calculator →
See the full air purifier ranking →