Air Purifiers

What is CADR Rating? Everything You Need to Know

What is CADR Rating


When shopping for an air purifies, one of the most critical specifications to consider is the appliance’s CADR rating.

CADR stands for Clean Air Delivery Rate and essentially represents the particle removal capacity of an air purifier within a given space. 

Read ahead to discover more about the CADR rating, why it matters, and how it's measured.

What is CADR Rating?

The CADR rating measures the number of contaminant particles that a given air purifier removes from the air, within a given space, and in unit time.

For example, if your air purifier has a CADR of 200 CFM (cubic feet/minute), it will clean the air within a space of 200 square feet, in 1 minute. Therefore, the higher the CFM of an air purifier, the faster the appliance works to clean air.

CADR metrics fall within 3 main categories: dust, pollen, and smoke. All the 3 categories have their respective CADR ratings because the particles they represent vary in size.

The choice of particles was inspired by the fact that the three are not only very small, physically, but they are also the most unwanted in the air we breathe.

Smoke has the smallest particle size of the three compounds. Its particles are considered ultra-fine because their size ranges between 0.1 and 0.3 microns.

Dust, as many have experienced, is very common in enclosed spaces, even at home. Its particle size is in the range of 0.5 to 3 micron, making dust significantly larger than smoke.

Finally, there’s pollen. It has notably large particles in the size range of 5 to 11 microns. Pollen, though less common, is the largest of the three categories of air pollutants.

For air purifiers, all the 3 particles have the highest possible score on the CADR scale. The maximum possible score for smoke and pollen is 450; and the same for dust is 400.

CADR Rating and Air Purifiers

CADR Rating and Air Purifiers


The Association of Home Appliance Manufacturers (AHAM) is responsible for standardizing the CADR rating. For this reason, this rating is synonymous with air purifiers.

With this standard, it is possible to compare the air-cleaning capabilities and performance of an air purifier to determine is it meets your demands.

When choosing an air purifier, the unit’s score in each of the 3 categories is very important because it reflects the appliance’s efficiency in removing the three particles from the air.

Ideally, the higher the score of an air purifier in each category, the more efficient it is in removing particles specific to the size range.

That said, there are other factors such as filter, fan, and motor technologies that determine the performance of an air purifier, alongside the CADR rating.

How is CADR Calculated?

Calculating the CADR purifier is a standardized ANSI/AHAM AC-1 test. It involves placing the unit in a room of 1,008 cubic feet in size. The room/chamber typically contains a pre-determined quantity of contaminants. The appliance is then turned on and allowed to run for 20 minutes.

After 20 minutes of continuous running, the air purifier is turned off, and the air in the chamber is tested for the 3 contaminants, against pre-test levels established before the process.

This approach ensures that an objective score is obtained for the air purifier’s capacity to remove different-sized contaminants from the air.

It’s worth noting, however, that the AHAM CADR rating program is voluntary. There is no legal obligation for brands and manufacturers to participate in the program.

Therefore, when shopping for an air purifier, you can maximize the chances of getting an efficient one by confirming the existence of a CADR rating on your models of choice.

Limits of CADR Rating

Limits of CADR Rating

Photo: Samsung

A key limitation of the CADR rating is that it only deals with 3 specific contaminants; smoke, dust, and pollen.

You may need a purifier for other contaminants such as bacteria or viruses. In such cases, the CADR ratings specified by AHAM will not apply to the air purifier you’re considering.

CADR assesses the performance of the air purifier for the first 20 minutes of its run time, only. This short testing duration fails to account for the decline in air performance decline over time.

Finally, the CADR rating is obtained by assessing purifiers at their highest ratings. Although this is the standard for most tests, the outcome can imply the unit has a consistently high efficiency even though performance may vary depending on different conditions.


Without a doubt, the CADR rating is essential to the determination of an air purifier’s efficiency.

The higher the CADR rating of your purifiers in the smoke, dust, and pollen category, the more efficient it is at eliminating these pollutant particles from the atmosphere.

And even though the rating has its limitations, it is a reliable indicator of the kind of performance to expect from your desired air purifier.

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