What is CADR rating?

To determine a strength of an electronic devices, we always look for all the common specs. For an air purifier, two of the most things we have heard a lot is the CADR rating and ACH rating. So what is CADR rating? What is ACH rating? You may ask these questions many times before purchasing any air purifiers, right?

However, the answer is really simple.

Air purifiers become more and more popular. People who suffer from allergies or asthma will no need to take more pain, as air purifier is one of the top solutions to help prevent allergies and asthma. Because of that, we will see more and more air purifiers used at home and other public places like schools, hospitals or any healthcare services. So are you ready to find out what is CADR rating and pick a right air purifier for you? Let Breathe Quality help you.

Note: If you need answer for common question of air purifier, please read our air purifier FAQs.

Air Purifier Definitions: 

What is CADR rating?

CADR stands for Clean Air Delivery Rate. In general, this numerical value will show you exactly how much of the specific particles to be removed from the air. In other words, CADR rating indicates how fast the air purifier can clean the air within a particular size room. For example, an air purifier with CADR rating of 300 cfm will clean a room of 300 sq ft much faster than an air purifier with CADR rating of only 200 cfm.

CADR rating is taken in CFM which stands for cubic feet per minute, or in m³/hour. CADR measurement is usually for pollen, smoke, and dust. These three pollutants are not only small in size but also the most unwanted particles in the air. Smoke particles are ultra-fine particles, with the defined particle size ranges from 0.1 to 0.3 microns. Dust particles are common particles with size from 0.5 to 3 microns. And pollen particles are the large particles that you can see with your own eyes, with size from 5 to 11 microns.

CADR ratings are invented by AHAM (Association of Home Appliance Manufacturers). It is safe to say that AHAM’s CADR rating is currently the most accurate measurement. To make use of the CADR rating, you can look for it whenever picking an air purifier. The better CADR ratings are, the more powerful this air purifier’s fan is. Here are some examples of air purifiers with high CADR rating.

Expert tips: Remember that CADR ratings only show only the cleaning capacity, not the cleaning capability.

It means an air purifier with high CADR ratings is indeed having a high fan power to cover a large size of room. If you want to know the cleaning capability, you should check for the filters and the technology of this air purifier. Knowing that you don’t have time and experience to test all these specs, Breathe Quality was born to help everyone check all the air purifiers with absolute authenticity.

Up until now, here are our trusted lists of best air purifiers at the moment (always up-to-date):

How to measure CADR ratings?

CADR ratings are strictly determined by an ANSI/AHAM AC-1 test. This test is simple to understand, but is really accurate. The testing agency will put the testing air purifier unit into a chamber with a determined amount of contaminants. After 20 minutes of running, they stop the air purifier and measure the air in this chamber one again. Finally, they can make conclusion of the CADR ratings for this air purifier.

However, this test has its own limits. CADR ratings is only for the specific contaminants and in this case, dust, pollen and smoke. If you need an air purifier for a specific kinds of virus or bacteria, AHAM’s CADR ratings just are not useful. Also, the short test of 20 minutes is a clear limit of this test, as some air purifiers are working fine for the first 20 minutes and then decline the performance rating later.

Also, the ionizer is one reason for making CADR ratings false. An ionization is a process of sticking many small particles into a bigger one, but not trapping them. Usually, these bigger formed particles are dropped on the floor and wall. Without a proper removal, these pollutant particles are ready to be in the air once again.

At the moment, we guess you understand the limit of CADR ratings. While this measurement is one key factor to choose the right air purifier, keep in mind that you should test other specs as well. An expensive air purifier will always better than a cheap one, even when it has a lower CADR rating. That’s mostly because they are using a higher quality filtration system.

What is ACH? Is ACH related to CADR ratings?

ACH stands for Air Changes per Hour. The ACH rating indicates how many times per hour an air purifier device can exchange the air within a room. More fresh air exchange means better air quality in general.

Together with CADR ratings, ACH rating shows exactly the power of this air purifier fan. In short, a 5X ACH air purifier will clean the specific size more times than a 2X ACH air purifier.

If you want to know how ACH is related to CADR ratings, let’s look at the example below:

You have a Honeywell HPA300 with an average CADR of 300 cfm. This air purifier can run as high as 5X ACH. So how much does the room size this Honeywell HPA300 can effectively clean?

Well, within 1 hour (or 60 minutes), Honeywell HPA300 can clean a capacity of: 300 x 60 = 18000 cfm.

With a room of typical 8 feet in ceiling height, you will have: 18000 (cfm)/8 (f) = 2250 (f².h)

Divide this value for the ACH, and you will have the answer: 2250 (f².h)/5 (h) = 450 f². Well, in the manual, Honeywell HPA300 is claimed to be effective in a room size of 450 sq ft.

We hope up until now, you fully understand “what is CADR rating” and “what is ACH“. Don’t forget that you can put full trust in Breathe Quality’s air purifier test. To give one list to you, we need to test hundreds of air purifiers in the market.

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