CADR Explained: PureAir Lab Guide to Air Purifier Ratings

CADR Explained

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When you shop for an air purifier, you'll run into the acronym CADR. It's one of the most useful numbers on a spec sheet — if you know how to read it. This guide explains what CADR means, how to use it to size a unit, and where it can mislead.

What CADR stands for

CADR is Clean Air Delivery Rate. It's a measure, popularized by an industry testing program, of how much filtered air a purifier delivers, typically reported separately for smoke, dust, and pollen. A higher CADR generally means the unit cleans a given room faster. We won't quote specific CADR figures for individual products here, because we haven't tested them and manufacturers' listed numbers should be your reference.

How to use CADR to size a purifier

A common rule of thumb pairs CADR with room area and air changes per hour:

• Bigger room or higher ceiling → you want a higher CADR.
• Want more air changes per hour (useful for allergies or smoke) → step up the CADR.
• A widely cited guideline suggests the smoke CADR should be in the neighborhood of two-thirds of the room's area in square feet, but treat that as a starting point, not gospel.

The practical takeaway: match a unit's listed CADR to your room, and size up if you want faster turnover. Running a higher-CADR unit on a lower, quieter speed is often more pleasant than maxing out a small one.

Where CADR falls short

• It's measured at max speed. Real-world, quieter operation delivers less.
• It doesn't capture odors/gases well. CADR is a particulate metric; carbon performance isn't reflected.
• It says nothing about filter longevity or running cost.

So CADR is a great first filter for shortlisting, but pair it with filtration quality (True HEPA, real carbon) and maintenance cost before deciding.

CADR vs. coverage rating

Many brands also publish a simple "recommended room size." That figure is usually derived from CADR assumptions. When both are listed, CADR is the more transparent number because it's tied to a defined test.

Putting it together

If you want units that are widely recommended and publish clear ratings, the Coway Airmega 400 (large rooms) and Levoit Core 600S (smart value) are common starting points.

See the Coway Airmega 400 → · Check the Levoit Core 600S →

And whatever you buy, budget for filter upkeep — it's the recurring cost behind every CADR figure. Browse replacement filters →

Bottom line

CADR tells you how fast a purifier cleans a room at full tilt, broken out for smoke, dust, and pollen. Use it to size up to your space, then sanity-check filtration quality and running cost. It's a starting point for a smart buy — not the whole story.