Quick answer: CADR (Clean Air Delivery Rate) measures how much clean, filtered air a purifier delivers per hour, usually in m³/h. A higher CADR isn't automatically "better" — the number only matters relative to your room size. The right way to compare purifiers is to match CADR to your actual room's area, not to chase the highest number on the shelf.
Most people shopping for an air purifier land on one spec above all others: CADR. It's on every box, every listing, every comparison chart — and it's also the number most often misread, usually as "bigger is simply better." It's more useful than that, but only once you know what it's actually telling you.
What CADR Actually Measures
CADR stands for Clean Air Delivery Rate — it tells you the volume of clean air a purifier can deliver in an hour, typically expressed in cubic meters per hour (m³/h) or cubic feet per minute (CFM) in some markets. In practice, it's a combined measure of two things: how much air the unit's fan moves, and how effectively its filter actually cleans that air. A high CADR number means more clean air output per hour — not necessarily better filtration quality on its own.
Why "Bigger Number = Better Purifier" Is the Wrong Read
Illustration generated for Kevelin
A purifier with a CADR of 400 m³/h isn't a better fit than one rated 200 m³/h — it depends entirely on the room it's going into. Oversizing has real downsides:
- Cost. Purifiers with higher CADR are typically priced higher and consume more power for a room that doesn't need that much air turnover.
- Noise. Larger fans moving more air tend to run louder, even at comparable "quiet mode" settings.
- Footprint. Higher-CADR units are usually physically larger, which matters in a bedroom, desk setup, or smaller apartment.
Undersizing has its own problem — a low-CADR unit in a large hall simply won't cycle the air often enough to make a meaningful difference.
The Actual Formula: Matching CADR to Room Size
The standard guideline used across most manufacturers is that a purifier should be able to cycle the air in a room roughly 4–5 times per hour for effective filtration. In practical terms, this means checking a purifier's stated coverage area (usually given directly, like "14–24 m²") against your actual room size, rather than comparing raw CADR numbers across purifiers built for different room categories.
A simple way to check it yourself: measure your room's floor area, then look for a purifier whose stated coverage range comfortably includes that number — not the bare minimum, and not dramatically oversized either.
What Else CADR Doesn't Tell You
CADR is genuinely useful, but it's one spec among several that matter:
- Filter type — CADR doesn't tell you if it's true HEPA + activated carbon or a lesser filtration combination (see our [HEPA vs ionizer breakdown]).
- Noise level at the CADR-rated speed — some purifiers only hit their advertised CADR at maximum fan speed, which is also their loudest setting.
- Running cost — higher CADR units generally cost more to run daily, which matters for anything running continuously (a bedroom, home office).
Where KEVELIN Breath Fits
KEVELIN Breath is rated at 200 m³/h CADR, matched specifically to rooms of 14–24 m² — the size of a typical bedroom, home office, or study, rather than an oversized number built for a hall it'll never actually sit in. Paired with true HEPA and activated carbon filtration, it's built to hit that CADR number at a genuinely everyday, low-noise setting — not just on paper at maximum speed.
The Bottom Line
CADR is worth checking, but it's a match-to-room-size number, not a bigger-is-better one. Measure your actual room, look for a purifier whose coverage range fits it comfortably, and then check filter type and noise level before deciding — CADR alone doesn't tell the full story, but paired with the right room match, it's the most useful single number on the spec sheet.
KEVELIN Breath — 200 m³/h CADR, matched to the room you're actually filtering. [Learn more at kevelin.in].
