The CADR Rating – Clean Air Delivery Rate Explained

CADR Defined

CADR, or Clean Air Delivery Rate, is a metric used for measuring the performance of air purifiers. Developed by the Association of Home Appliance Manufacturers (AHAM), the CADR rating will tell you the volume of air in CFM (cubic feet per minute) cleaned by the air purifier. In other words, it tells you how many cubic feet per minute of air is stripped of particles of various sizes.

If you look at the specifications of different air purifiers, three CADR ratings are usually given: one each for dust, pollen, and smoke. These represent three classes of airborne pollutants in terms of size: large, medium, and small, respectively. So, if you want to know how well a specific model rids the air of large particles, you should look at its CADR rating for dust. On the other hand, its CADR rating for smoke will tell you how it performs against small particle pollutants.

CADR Benefits

In a nutshell, the CADR is the product of an air purifier’s air flow and the efficiency of its filters. With that said, looking at the CADR will give you a balanced view of the air purifier’s performance. The CADR lets you gauge an air purifier’s cleaning ability compared to other popular metrics, such as filter efficiency.

For example, those who’ve shopped for air purifiers have probably already heard of True HEPA filters. A True HEPA filter is known to remove up to 99.97% of all the particles passing through it. While this filter efficiency may be impressive, it doesn’t actually tell you how fast the air purifier provides clean, purified air. If this True HEPA unit has mediocre airflow, it will end up with a much lower clean air delivery rate than, say, another model whose filter efficiency is at a slightly lower than 99% but processes air at a much higher rate.

Conversely, an air purifier that can take in a huge volume of air per minute, but if the filter efficiency isn’t too impressive it will likely have lower CADR ratings as well. With all that being said, looking at an air purifier’s CADR ratings will help you avoid getting misled by marketing claims, as it provides much more insight than air intake (usually in CFM) and filter efficiency (usually in percentages) alone.

CADR Calculations

CADR ratings are determined by running the air purifier at its highest fan speed inside a 1008 cu. ft. testing chamber and consequently measuring the number of particles that it has successfully removed after 20 minutes of operation. This is done for each type of particle (small, medium, and large). Because the test is always conducted within a 1008 cu. ft. space, air purifiers can score within the following CADR lower and upper limits:

  • 10 to 400 CFM for dust
  • 25 to 450 CFM for pollen
  • 10 to 450 CFM for smoke

Also, note that the test is conducted using fresh filters.

Using CADR for Model Comparisons

As mentioned previously, CADR ratings provide a balanced view of how different air purifiers perform. This makes it a good means of comparison when you’re out shopping for an air purifier.

However, while looking at CADR ratings is a good practice, know that the system is far from perfect. Below are the limitations of the CADR system:

  • Since CADR ratings are measured while using an air purifier’s highest fan speed, it might not be an accurate reflection of the cleaning power you’ll enjoy if you prefer to use lower fan speeds to minimize noise level and/or power consumption.
  • The CADR only measures the performance of an air purifier’s filters and tech against particle pollutants. That said, it doesn’t take into account how air purifiers perform against other airborne contaminants like VOCs, ultra-fine particles, and odors.
  • CADR tests are done with brand-new units using clean filters. As such, it will not be an accurate representation of how your air purifier will perform down the road. For example, Air Purifier A might be better than Air Purifier B at the time of testing. But if Air Purifier A has a thinner filtering media than Air Purifier B, its performance might deteriorate a lot faster after a couple of days.

Final Thoughts

CADR ratings provide consumers a way to objectively compare air purifiers. Looking at CADR ratings for dust, pollen, and smoke is definitely a better practice than buying blindly or simply relying on qualitative marketing messages.

The set of limitations discussed above, though, means that this system of comparing different models isn’t perfect. Other factors, such as filter size or thickness, noise level, power consumption, and the presence of non-mechanical technologies, should also be considered on top of an air purifier’s CADR. The table below summarizes the pros and cons of CADR ratings.


  • They allow for the quantification of an air purifier’s cleaning ability
  • They provide an objective way for consumers to compare different models
  • They show an air purifier’s performance in removing small, medium, and large particles


  • They aren’t an accurate representation of performance down the road
  • They don’t tell you how well different models fight VOCs, odors, and microscopic particles
  • They only take into account the performance of an air purifier on its highest speed setting


  • Julia

    Thank you for the useful article, I never actually understood what that rating stood for until now!

  • Theo

    Buying an air purification system isn’t easy at all as you do need to know what certain specs stand for. Now that I fully understand what the CADR rating actually stands for, it will be a lot easier for me to choose the perfect purification system for home use. Thanks for your help!

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