What is CADR Rating in Air Purifier? | is higher CADR better?

Let us understand the concept of CADR and its significance in air purifiers.

What is CADR?

In simple terms, CADR stands for Clean Air Delivery Rate. It indicates how effectively and quickly does your air purifier purifies the indoor air. It helps you understand how effective your air purifier is in removing contaminants and delivering pure air to the room.

For example, you will find air purifiers declaring that the maximum airflow of the air purifier is 300 cubic feet per minute (CFM). It entails that your air purifier can process 300 cubic feet of air in a minute. However, it does not show how efficient the purifier is when dealing with contaminants like smoke, pollen, and dust. The CADR gives you the perfect picture of the air purifier’s efficiency.

For an air purifier with a 300 CFM airflow, the CADR should be around 200 (We shall see the 2/3 AHAM ruling later in the article.). This rating indicates that the air purifier can effectively purify 200 CFM of air.

Who decides the CADR?

AHAM (Association of Home Appliance Manufacturers), an independent body, conducts CADR tests on the air purifiers. However, the CADR is not a mandatory requirement. Hence, manufacturers can voluntarily submit their air purifiers to AHAM for CADR testing. Since the CADR tests are standard for all air purifiers, you get a desired level of consistency.

CADR – The Definition

The AHAM definition of CADR can be confusing. It defines CADR as follows.

CADR = (Rate of reduction of the contaminant in the test chamber when the air purifier is turned on minus the natural decay rate when the unit is switched off) multiplied by the test chamber volume.

CADR is different for the following three categories of pollutants, dust, pollen, and smoke. For example, the highest possible CADR rating for dust is 400, whereas it is 450 for smoke and pollen.

How does AHAM calculate CADR?

The air purifying machine is placed in a room measuring 1008 cubic feet in volume. The pre-test levels of contaminants is conducted beforehand. The air purifier runs for 25 minutes, after which the contaminant levels are tested again. It gives you an indication of how effective the air purifier is in removing these three contaminants, smoke, dust, and pollen.

Thus, an air purifier should effectively have three CADRs,

• Smoke CADR – deal with smoke particles between 0.9 and 1.0 micrometers.
• Dust CADR – to eliminate dust particles in the range of 0.5 and 3 micrometers.
• Pollen CADR – deals with pollen particles between 5 and 11 micrometers.

The higher the CADR, the better it is, as the air purifier filters more air per minute for the specific particle size.

What is the recommended CADR?

While every air purifier manufacturer should conduct CAHAM rating tests, many manufacturers do not do so. Under such circumstances, AHAM prescribes the 2/3 rule.

For example, if the purifier manual states that the maximum airflow of the machine is 300 CFM, the CADR rating is 2/3 of 300, 200CFM.

Similarly, if the airflow is 200 CFM, the CADR rating is 133 CFM. Thus, it should give you a fair idea of what the CADR of a specific air purifier is.

Benefits of knowing the CADR

• CADR provides information on how well the air purifier filters out smoke, dust, and pollen. A comparison with other air purifiers that have undergone the tests could give you a better perspective.
• CADR rating helps you decide on the ideal air purifier for your home. For example, if you live in places having a high volume of industrial smoke contamination, you can choose an air purifier with a high Smoke CADR rating. Similarly, if you reside in dusty areas, you can go for air purifiers having a higher Dust CADR rating.
• The primary benefit of CADR rating is that it introduces the transparency element because each air purifier has to undergo similar tests under pre-set conditions by a third-party neutral tester.

Drawbacks of CADR

• Though CADR provides the effectiveness of purifying the air of smoke, dust, and pollen, it does not present a complete picture of the air purifier’s efficiency in dealing with other pollutants, like gases, odors, or VOCs. Therefore, the CADR should not be the sole metric for deciding the ideal air purifier for your home. Instead, it helps if you also looked at aspects like HEPA filters, carbon filters, etc., to deal with other pollutants.
• CADR rating tests are done with the air purifier running at the highest settings. However, you do not usually run the air purifier at the highest settings at home because of the noise disturbances they create. Therefore, you get an inflated efficiency level of your air purifier.
• CADR ratings are done with the air purifiers working for 25 minutes. However, you use the air purifier for an extended duration at home. The continuous usage of the air purifier can leave the HEPA and other filters clogged with contaminants. Hence, the CADR of a brand-new machine will be more than a used unit.

Final Thoughts

While CADR ratings have their benefits and drawbacks, they provide you with information regarding the air purifier’s efficiency in dealing with smoke, pollen, and dust impurities. If your primary concern is removing these impurities from your indoor air, the CADR rating is critical.

While CADR ratings are crucial, you have to look at other features of the air purifier, especially the type of filters and the filtration methods. Nevertheless, the CADR rating influences your purchase decision considerably.